ENDOCRINOLOGY

INTRODUCTION

• Endocrinology – study of the endocrine system

• Encompasses knowledge of the functions of the endocrine system, endocrine glands, types and functions of hormones especially in the regulation of the physiological activities of the body

Functions of the endocrine system

• The endocrine and nervous systems are two regulatory systems of the body

• Compared to neural activity, the action of hormones is usually slower and prolonged

• The endocrine system mainly controls activities that require a longer duration.

• Eg: Help in maintaining homeostasis and regulation of activities such as the concentration of chemicals in body fluids and metabolism of lipids, carbohydrates and proteins

• Work closely with the nervous system to help the body combat stress

• Assist in the regulation of growth and development especially in maturity, sexual development and reproduction

The endocrine system is a complex system

• One endocrine gland can produce multiple hormones. A single hormone can be produced by more than one endocrine gland.

• A single hormone can have more than one type of target cell therefore, more than one effect. Also, a single target cell can be influenced by more than one hormone.

• Other factors contribute to the complexity of the system. The rate of secretion of a hormone can vary over time.

• The same chemical messenger can be a hormone or neurotransmitter (e.g., norepinephrine).

• Some organs have exclusively endocrine functions. Other organs (e.g., testis) have endocrine functions and non-endocrine functions.

Hormone

• Special chemical substances produced and secreted by endocrine cells/tissues/glands

• Effective even in small quantities• Balanced by other hormones• Can act on cells located far away, nearby

or on the cell that secretes the hormone• Helps to regulate the rate of biochemical

reactions• Is not influenced or changed by the

reactions that it controls

HormoneCan be categorized by its solubility:1.   Water soluble (hydrophilic) eg: peptide and protein hormones

are transported freely in blood2. Fat soluble (lypophilic) eg: steroid hormones and

prostaglandins are transported in blood by binding to plasma proteins

Can be categorized according to its chemical structure:1. Acid amino derivatives (amines and secreted by adrenal

medulla with the main aa being tyrosine)2. Peptide hormones (small peptides, polypeptides,

glycoproteins)3. Lipid derivatives (steroid hormones and eicosanoids)

(steroid hormones are secreted by the adrenal cortex and gonads)

 Examples of hormones

1. Protein hormones – Growth Hormone (GH), prolactin and insulin

2. Glycoprotein hormones – Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), Thyroid Stimulating Hormone (TSH) and Parathyroid Hormone (PTH)

3. Polypeptide hormones – oxytocin, calcitonin, glucagon4. Acid amino derivative hormones – adrenaline

(epinephrine), noradrenaline (norepinephrine), melatonin, dopamine, thyroid hormones

5. Lipid/steroid hormones – testosterone, estrogen, corticosteroids, cortisol

6. Fatty acid hormones/eicosanoids – thromboxane, leucotriene and prostaglandins

The mechanisms of hormone synthesis, storage, and secretion vary according to the class of hormone• Peptide hormones have precursors called preprohormones

made on ribosomes of the endoplasmic recticulum (ER). Are converted to prohormones and active hormones in the Golgi complex. The Golgi complex concentrates these hormone into secretory vesicles which are then eleased from endocrine cells by exocytosis

• Cholesterol is the common precursor for all steroid hormones.

A series of enzymatic steps modify this molecule into a different hormone in a specific endocrine cell. Only the precursor (cholesterol) is stored. The lipid-soluble hormone is not stored

• The amine hormones are made from tyrosine. These

hormones are stored until they are secreted

Regulatory feedback mechanisms

• Hormones are secreted in a fixed amount to maintain homeostasis, i.e., not secreted continuously

• Why? Any changes in the body’s physiology will be detected by the brain (main control center) where actions has to be taken to maintain homeostasis

• Therefore secretion of hormones are dependant on a feedback mechanism

• This regulatory feedback mechanism is either positive or negative, long loop or short loop

• Example of a positive and negative feedback mechanism is the regulation of the functions of the female reproductive system

• Example of a long loop and short loop feedback mechanism is the regulation of the body systems under stressful conditions

Interactions of hormones with target cells

What are target cells?Target cells are:• cells that possess a receptor that is

compatible to the hormone and is located either on the plasma membrane surface or in the cytoplasm or nucleus

• influenced by certain hormones

• Hormones that combine with receptors will influence the rate of cell physiological processes

• Down regulation is a decrease in the number of receptor molecules in target cells

• Up regulation is an increase in receptor molecules of target cells

Types of hormone receptors

• Receptors that are located on the membrane or membrane surface will bind to hydrophilic hormones or hormones that have a large molecular weight

• Receptors that are located intracellular (in the cell) will bind to lypophilic hormones

Mechanism of hormone action

• Act by binding to special receptors on target organs

• A hydrophilic hormone binds to the target cell surface and activates a second-messenger system

Eg; Protein hormones will bind to receptors on the surface of the plasma membrane of the target cell

• require a messenger i.e., second messenger e.g., cAMP (cyclic adenosine monophosphate) present in the extracellular fluid to trigger a biologic reaction

eg., insulin

• A lipophilic hormone stimulates a gene, promoting protein synthesis

Eg;Steroid hormones have a receptor in the cell and can diffuse freely into cells because it is lypophilic

• After binding with the cytoplasmic receptors in the target cells, it will trigger a physiological reaction

eg., estrogen

Mechanism of hormone action for protein hormones

(hydrophilic)Hydrophilic hormones secreted by endocrine glands

Travel freely in blood vessels until reach target

organs

Bind with receptor on surface of plasma membrane

Hormone-receptor complex stimulates G protein

G protein connects this complex to adenyl cyclase enzyme in the inner surface of the cell

Activated adenyl cyclase converts ATP to cAMP

cAMP activates protein kinases

Protein kinases trigger a cascade of enzyme reaction

Causes cells to undergo certain functionsi.e., release of energy from hepatic cells

After cells have completed their physiological functions, cAMP is

deactivated by phosphodiesterases

Location of receptor on the plasma membrane returns to its origin and ready to receive new hormones

Firstmessenger, usually an extracellularchemicalmessenger

G proteinintermediary

Plasmamembrane

ECF

Receptor

Binding of extracellularmessenger to receptoractivates a G protein, the subunit of which shuttlesto and activates adenylcyclase

(Converts)

(Activates)

(Phosphorylates)

(Phosphorylation inducesprotein to change shape)

Second messenger

= phosphate

ICFAdenylcyclase

Mechanism of steroid hormones (lypophilic)Lypophilic hormones are secreted

Transported in blood by binding to plasma proteins

Released by plasma proteins on reaching target cells

Diffuses through plasma membrane and binds to receptor inside cytoplasm

Hormone receptor complex enters cell nucleus and binds to cell DNA

Triggers DNA transcription and produces mRNA

Directs protein synthesis

eg:breast development under estrogen influence and development of dense muscular mass under testosterone influence

Plasmamembrane

Cytoplasm of target cell Nucleus

H = Free lypophilic hormoneR = Lypophilic hormone receptor

HRE = Hormone response elementmRNA = Messenger RNA

Hormone excretion• Hormones will be excreted after completing its

functions• Hydrophilic hormones have a short life span while

lypophilic hormones have a longer life span • Life span of hormones is termed ‘half-life’

Rate of hormone excretion

• Rate of hormone excretion is dependant on the plasma concentration of that hormone which is regulated by changes in its rate of secretion i.e.,

a. Hormone’s rate of secretion by the endocrine gland (major factor for all hormones)

b. Its rate of metabolic activation (for a few hormones)

c. Its extent of binding to plasma proteins (lipophilic hormones)

d. Its rate of metabolic inactivation and excretion (for all hormones)

Types of hormone excretion1. Rapid excretion – through the kidney into urine or the liver

into bile

2. Metabolism - destroyed by enzymes in the blood, liver, kidney, lungs and target cells

3. Active transport – some hormones are transported into cells and reuse as hormone substance or neurotransmitter

4. Conjugation – substances like acid sulphates and glucoronic acids will bind to hormones in the liver and render it less active as a hormone and increase its rate of excretion into urine or bile

Plasma

Endocrine glandHormone boundto plasma proteins

Free, biologicallyactive hormone

Target cellsMetabolism inliver or other tissues

Physiologicresponse

Excretion inurine

Secretion

Binding(lipophilichormones)

Activation(some hormones)

Inactivation

Hormone lifespan

Hormone lifespan can be prolong by:• Protection from rapid excretion by binding

to plasma proteins eg., lypophilic hormones

• Protection from proteolytic enzymes in the circulatory system by having a carbohydrate component in their chemical structure eg., glucoprotein hormones

Hormone interactionsFour types of interactions exist:

1. Antagonistic – interaction is opposite each other eg: calcitonin and parathyroid hormone

2. Synergistic – hormones interact so that the end result will be more meaningful as compared to if only one hormone is functioning/several hormones complement each other and combine effects eg: stimulation of mammary glands development by prolactin, estrogen, progesterone and growth hormone

3. Permissive – a pattern of interaction whereby one hormone must be present in sufficient amounts for the full effect of another hormone to occur. eg; adrenaline needs thyroid hormones for energy production

4. Integrative – an interaction whereby many hormones regulate the different body physiological systems eg: calcitriol and PTH effects on tissues involved in calcium metabolism

Other hormones• Leukotrienes, together with prostaglandins

and other related compounds, are derived from 20 carbon (eicosa) fatty acids that contain double bonds (enoic), hence this group of substances is called the eicosanoids.

• The name leukotriene derives from the original discovery of these substances in white blood cells (polymorphonuclear leucocytes) and the fact that they all have in common 4 double bonds (hence the 4 subscript), 3 of which are in a conjugated triene structure.

• Leukotrienes do not exist preformed in cells

• They are formed from the breakdown of arachidonic acid, a polyunsaturated 20 carbon fatty acid.

• In its esterified form, arachidonic acid is bound to the phospholipids of the cell membranes

• Both immunological and non-immunological stimuli can release arachidonic acid from membrane phospholipids by activating phospholipase A2

• The glucocorticosteroid drugs can inhibit phospholipase A2 and thereby decrease the production of all the leukotrienes and hence leukotriene-mediated responses

Endocrine disorders• Due to hyposecretion or hypersecretion of a hormone.• Factors producing hyposecretion include heredity, dietary

deficiency, immunologic factors, and disease processes. • Hyposecretion can be primary or secondary (due to the

deficiency of the hormone’s tropic hormone).• Replacement therapy of a hormone can often successfully

treat the conditions from hyposecretion.• Hypersecretion of a hormone can also be primary or

secondary. • Factors producing hypersecretion include tumors on the

endocrine gland and immunologic factors. • Endocrine dysfunction can also arise from the

unresponsiveness of target cells to a hormone.

Hormone release1. From hypothalamus to anterior

pituitary- ‘releasing’ or ‘inhibiting’ hormones

from the hypothalamus are secreted into the HHP tract to the anterior pituitary. Specific hormones from the AP are then secreted into the same blood vessels to be transported to target cells

• Therefore robust control systems must be present to prevent over or under-secretion of hypothalamic and anterior pituitary hormones.

• A prominent mechanism for control of the releasing and inhibiting hormones is negative feedback

Hormone release2. From hypothalamus to posterior pituitary- Neurohormones from posterior pituitary

glands are produced by neurosecretory cells whose cell bodies are located in the hypothalamus

- These axons from the cell bodies enters the infundibulum of the posterior pituitary gland

- Gives rise to a nerve tract called Hypothalamic-Hypophyseal Tract (HH)

Hormone release- neurohormones enters axons and are stored

in the shape of small secretory vesicles a. Action potentials from the neurone cell

bodies in the hypothalamus travels down the axons until they reach the axon terminals in the posterior pituitary glands via the HH tract

b. These action potentials causes neurohormone release

c. These neurohormones then enters the blood stream

Hypothalamic hypophyseal portal veins

Pituitary GlandAnatomy of the pituitary gland:

• The pituitary gland is as large as a pea, and is located at the base of the brain

• The gland is attached to the hypothalamus by nerve fibers

• The pituitary gland itself consists of three sections:

• the anterior lobe (pars tuberalis)• the intermediate lobe (pars intermedia)• the posterior lobe (pars distalis)

Pituitary gland• The anterior pituitary (adenohypophysis) is a

classical gland composed predominantly of cells that secrete protein hormones

• The posterior pituitary (neurohypophysis) is not really an organ, but an extension of the hypothalamus

• Composed largely of the axons of hypothalamic neurons which extend downward as a large bundle behind the anterior pituitary

• It also forms the pituitary stalk, which appears to suspend the anterior gland from the hypothalamus

Anatomy of the pituitary gland

• Each lobe of the pituitary gland produces certain hormones

anterior lobe:• growth hormone (GH) (non-tropic

hormone)• prolactin (non-tropic hormone)• ACTH (adrenocorticotropic hormone) • TSH (thyroid-stimulating hormone) • FSH (follicle-stimulating hormone) • LH (luteinizing hormone)

Anatomy of the pituitary gland

intermediate lobe:• melanocyte-stimulating hormone (non-tropic

hormones)

posterior lobe:• ADH (antidiuretic hormone)/vasopressin • Oxytocin

• Tropic hormones – their target cells are other endocrine glands

How is it possible for the anterior pituitary gland to produce so many different hormones?

-Because the tissues are so specialized

-They contain three types of cells which can be distinguished by staining

-Red stained cells/acidophils will produce GH and PRL

-Blue stained cells/basophils will produce TSH, FSH, LH, MSH and maybe ACTH

-Unstained cells/chromophobe) which is a variation of both acidophils and basophils may also produce ACTH

Functions of pituitary Functions of pituitary hormoneshormones

GROWTH HORMONE (GH)GROWTH HORMONE (GH)

Somatotropin. Effective on all body sections Somatotropin. Effective on all body sections involved in growth involved in growth

Have a dramatic effect on the growth rate of Have a dramatic effect on the growth rate of children and adolescents where it increases tissue children and adolescents where it increases tissue mass and stimulates cell division mass and stimulates cell division

Its secretion is controlled by GH-RH and GH-IH Its secretion is controlled by GH-RH and GH-IH from the hypothalamus. This hormone is released from the hypothalamus. This hormone is released in a pulsatile rhythm. in a pulsatile rhythm.

Functions of GH:Functions of GH:

maintains the epiphyseal discs at long bonesmaintains the epiphyseal discs at long bones

stimulates the rate of growth by increasing RNA stimulates the rate of growth by increasing RNA development that will promote rate of protein synthesisdevelopment that will promote rate of protein synthesis

decreases protein denaturationdecreases protein denaturation

promotes use of fat for energy by storing CHOpromotes use of fat for energy by storing CHO

changes body composition to have more muscle mass as changes body composition to have more muscle mass as compared to fat depositioncompared to fat deposition

If too much GH is secreted at the end of the adolescent If too much GH is secreted at the end of the adolescent stage, gigantism will occur where the height will reach 7 stage, gigantism will occur where the height will reach 7 to 8 feet tall to 8 feet tall

If less GH is secreted at a young age, then a premature If less GH is secreted at a young age, then a premature closure at the epiphyseal discs occur and the body will closure at the epiphyseal discs occur and the body will stop growing therefore causing a condition called stop growing therefore causing a condition called cretinism or dwarfism cretinism or dwarfism

If normal development has stopped but GH is still If normal development has stopped but GH is still secreted, then a condition called acromegaly occurs secreted, then a condition called acromegaly occurs where the bones at the skull, hands and feet thickenswhere the bones at the skull, hands and feet thickens

Too much GH secreted will cause hyperglycemia, Too much GH secreted will cause hyperglycemia, because the beta cells of the pancreas that secretes because the beta cells of the pancreas that secretes insulin are stimulated causing diabetes mellitusinsulin are stimulated causing diabetes mellitus

AcromegalyAcromegaly

GigantismGigantism

Adrenocorticotropic Adrenocorticotropic hormone (ACTH)hormone (ACTH)

Stimulates the adrenal cortex gland to Stimulates the adrenal cortex gland to synthesis and release glucocorticoidssynthesis and release glucocorticoids

ACTH secretion is regulated by (C-RH) ACTH secretion is regulated by (C-RH)

or corticotrophin from hipothalamus. or corticotrophin from hipothalamus.

C-RH is regulated by a feed-back C-RH is regulated by a feed-back mechanism system that is influenced by mechanism system that is influenced by stress, the homone insulin, interleukin stress, the homone insulin, interleukin and other hormonesand other hormones

Melanocyte Stimulating Melanocyte Stimulating Hormone (MSH)Hormone (MSH)

Real function unknown Real function unknown

May play a role in the darkening of skin because May play a role in the darkening of skin because skin will look pale without MSH.skin will look pale without MSH.

MSH release is regulated by two hormones from MSH release is regulated by two hormones from the hipothalamus that is MSH-RH and MSH-IHthe hipothalamus that is MSH-RH and MSH-IH

MSH is secreted by the pars intermedia during MSH is secreted by the pars intermedia during the fetal stage, during childhood and to pregnant the fetal stage, during childhood and to pregnant women and also in some diseases. MSH is women and also in some diseases. MSH is usually not detected in mature human bloodusually not detected in mature human blood

HyperpigmentationHyperpigmentation

Thyroid stimulating hormone Thyroid stimulating hormone (TSH)(TSH)

Stimulates the synthesis and secretion of the hormones Stimulates the synthesis and secretion of the hormones thyroxine and triiodothreoinine. Goiter occurs when the thyroxine and triiodothreoinine. Goiter occurs when the thyroid gland enlarges due to too much TSH stimulationthyroid gland enlarges due to too much TSH stimulation

TSH secretion is controlled by T-RH from hipothalamus. TSH secretion is controlled by T-RH from hipothalamus.

T-RH release depends on the concentration of TSH and T-RH release depends on the concentration of TSH and thyroid hormones in the blood, metabolic rate of the body thyroid hormones in the blood, metabolic rate of the body and the surrounding temperatureand the surrounding temperature

Anti-diuretic hormone Anti-diuretic hormone (ADH)(ADH)

Vasopressin. Vasopressin.

Functions in urine production and assist in regulating fluid Functions in urine production and assist in regulating fluid balance in the bodybalance in the body

Target organ is the kidney. Target organ is the kidney.

ADH increases kidney tubules permeability to water so > ADH increases kidney tubules permeability to water so > water is reabsorbed into the body and not excreted as water is reabsorbed into the body and not excreted as urineurine

If ADH < secreted, a lot of water will be lost up to 23 liters If ADH < secreted, a lot of water will be lost up to 23 liters daily causing a condition called diabetes insipidusdaily causing a condition called diabetes insipidus

Secretion of ADH will increase in a Secretion of ADH will increase in a response to emotional or physical stress, response to emotional or physical stress, plasma osmotic pressure increases, plasma osmotic pressure increases, decreased extracellular fluid volume due decreased extracellular fluid volume due to high blood loss, heavy exercise and to high blood loss, heavy exercise and intake of nicotine or barbituratesintake of nicotine or barbiturates

Secretion of ADH will decrease as a Secretion of ADH will decrease as a response to low plasma osmotic response to low plasma osmotic pressure, increased extracellular fluid pressure, increased extracellular fluid volume and a high level of alcohol in volume and a high level of alcohol in bloodblood

PROLACTIN (PRL)PROLACTIN (PRL) Have two functions in women. Along with Have two functions in women. Along with

estrogen, they stimulate the development of the estrogen, they stimulate the development of the ductal system in the mammary glands during ductal system in the mammary glands during pregnancy. pregnancy.

Prolactin also synthesize milk after parturitionProlactin also synthesize milk after parturition

Prolactin release can be inhibited by (P-IH) or Prolactin release can be inhibited by (P-IH) or dopamine from hipothalamus. This inhibition is dopamine from hipothalamus. This inhibition is high in non-pregnant women or non-breastfeeding high in non-pregnant women or non-breastfeeding women. This inhibition is lifted during pregnancy.women. This inhibition is lifted during pregnancy.

Luteinizing Luteinizing Hormone(LH)Hormone(LH)

Also known as Interstitial Cell Stimulating Also known as Interstitial Cell Stimulating Hormone (ICSH) in the male reproductive systemHormone (ICSH) in the male reproductive system

Is a gonadotrophic hormone that stimulates Is a gonadotrophic hormone that stimulates ovulationovulation

Stimulates progesterone and a little bit of Stimulates progesterone and a little bit of estrogen release from the corpus luteum estrogen release from the corpus luteum

Target cells in male is the Leydig cellsTarget cells in male is the Leydig cells

Release of LH is dependant on Gn-RH from the Release of LH is dependant on Gn-RH from the hipothalamus which is regulated by a feedback hipothalamus which is regulated by a feedback mechanism involving progesterone, estrogen and mechanism involving progesterone, estrogen and testosterone levels in the bloodtestosterone levels in the blood

Follicle Stimulating Follicle Stimulating Hormone (FSH)Hormone (FSH)

Also a gonadotropic hormone.Also a gonadotropic hormone.

Stimulates follicular growth in the ovary at each Stimulates follicular growth in the ovary at each menstrual cycle and also stimulates cells in the menstrual cycle and also stimulates cells in the testes to produce spermatozoatestes to produce spermatozoa

Stimulates the follicles to secretes estrogen and Stimulates the follicles to secretes estrogen and the Gn-RH from the hypothalamus is the the Gn-RH from the hypothalamus is the regulatory factor for FSH releaseregulatory factor for FSH release

How do FSH and LH affects both the male and How do FSH and LH affects both the male and female reproductive system?female reproductive system?

Both hormones stimulate and gave the Both hormones stimulate and gave the same response to two different tissues same response to two different tissues (testes and ovaries) because both (testes and ovaries) because both organs/gonads have the same embryonic organs/gonads have the same embryonic origins origins

FSH is related to the production of sex FSH is related to the production of sex cells for both males and females while cells for both males and females while LH is related to the release of sex LH is related to the release of sex hormoneshormones

OxytocinOxytocin

Stimulates smooth muscle contractility Stimulates smooth muscle contractility at the myometrium of the uterus before at the myometrium of the uterus before parturitionparturition

Uterus will be sensitive to oxytocin at Uterus will be sensitive to oxytocin at the end of pregnancythe end of pregnancy

Release of oxytocin increases when Release of oxytocin increases when estrogen increase close to parturitionestrogen increase close to parturition

Will also stimulate myoephitelial cells Will also stimulate myoephitelial cells surrounding the ductal region of the breast surrounding the ductal region of the breast to ejects milk during lactation to ejects milk during lactation

Nipple stimulation by the baby will send a Nipple stimulation by the baby will send a nerve impulse to the hipothalamus to cause nerve impulse to the hipothalamus to cause the posterior pituitary to release oxytocinthe posterior pituitary to release oxytocin

Works together with prolactin throughout Works together with prolactin throughout lactation periodlactation period

Thyroid glandsThyroid glands Located in front of the trachea on the neck regionLocated in front of the trachea on the neck region Made up of two lobes connected to each other by Made up of two lobes connected to each other by

a bridge (isthmus). a bridge (isthmus). Possess a very efficient circulatory system (80-100 Possess a very efficient circulatory system (80-100

ml blood/min)  ml blood/min)   Made up of thousands of spherical gelatinous sacs Made up of thousands of spherical gelatinous sacs

where the thyroid hormones are keptwhere the thyroid hormones are kept Two types of cells: follicular cells (abundance) and Two types of cells: follicular cells (abundance) and

parafollicular cells (bigger but less).parafollicular cells (bigger but less). Follicular cells synthesize and secretes thyroxine Follicular cells synthesize and secretes thyroxine

((tetraiodotreionine T4) tetraiodotreionine T4) and triidothreoinine (and triidothreoinine (T3)T3) Made up of iodine and thyroxineMade up of iodine and thyroxine Parafollicular cells synthesize and secretes Parafollicular cells synthesize and secretes

calcitonincalcitonin

Function of Thyroid hormones

Control metabolic rate by > rate of 02 consumption by cells and organic molecules = energy and heat (> 02 consumption by all cells except brain, spleen and testes. The process of energy and heat poduction – calorigenic process)

Work with GH to regulate growth and maturity and also the development of the CNS

CVS becomes > sensitive to the symphatetic nervous system i.e., CO and HR increases

stimulates celluar differentiation and protein synthesis stimulates skeletal growth in children effective on maturity and the homeostasis of the skeletal

system and CNS

< thyroid hormones – < thyroid hormones – hypothyroidism, hypothyroidism, cretinism (if this happens cretinism (if this happens during prenatal during prenatal development, mental development, mental disability and abnormal disability and abnormal growth of bones and growth of bones and muscles occursmuscles occurs

> thyroid hormones – > thyroid hormones – hyperthyroidism, goitrehyperthyroidism, goitre

Regulation of thyroid hormonesRegulation of thyroid hormones

The secretion of thyroid hormones is The secretion of thyroid hormones is regulated by TSH regulated by TSH

TSH is secreted if < thyroid hormones in TSH is secreted if < thyroid hormones in the blood, when too cold or under stress the blood, when too cold or under stress or pregnancyor pregnancy

TSH is inhibited when the thyroid hormone TSH is inhibited when the thyroid hormone levels are > in the blood. levels are > in the blood.

The –ve and +ve feedback mechanism The –ve and +ve feedback mechanism control the secretion of thyroid hormonescontrol the secretion of thyroid hormones

Parathyroid glandsParathyroid glands Pea-shaped and embedded in the posterior lobe Pea-shaped and embedded in the posterior lobe

of the thyroid gland.of the thyroid gland. Each lobe will have a pair of parathyroid glandsEach lobe will have a pair of parathyroid glands Due to its small size, this gland was only Due to its small size, this gland was only

discovered in 1850. Before its discovery, it is discovered in 1850. Before its discovery, it is usually accidentally removed during thyroid usually accidentally removed during thyroid surgery and patients dies afterwards.surgery and patients dies afterwards.

Consists of principal or chief cells which Consists of principal or chief cells which secretes parathyroid hormone or parathormone secretes parathyroid hormone or parathormone and oxyphilic cells of unknown functionand oxyphilic cells of unknown function

Hormone secretion is dependent on the Hormone secretion is dependent on the concentration of calcium and phosphate ions in concentration of calcium and phosphate ions in the bloodthe blood

Parathyroid hormone (PTH)Parathyroid hormone (PTH) Increases calcium ions in the blood Increases calcium ions in the blood

whenever calcium concentration falls below whenever calcium concentration falls below normalnormal

Interacts antagonistically with calcitoninInteracts antagonistically with calcitonin Increases Ca in the blood by stimulating Increases Ca in the blood by stimulating

osteocyte activity in destruction of bone osteocyte activity in destruction of bone tissue and releasing the Ca into the bloodtissue and releasing the Ca into the blood

Stimulates Ca and POStimulates Ca and PO44 absorption in the absorption in the small intestines and reabsorption of Ca and small intestines and reabsorption of Ca and POPO44 by the kidneys by the kidneys

Decreases the concentration of PODecreases the concentration of PO44 in the in the blood by inhibiting reabsorption in kidney blood by inhibiting reabsorption in kidney and increasing its excretion into urineand increasing its excretion into urine

Calcium homeostasisCalcium homeostasis

Thymus gland Thymus gland A bi-lobe lymphoid organ located at the back of A bi-lobe lymphoid organ located at the back of

the sternum on the anterior mediastinum. the sternum on the anterior mediastinum. Cortex (high lymphocytes) and medulla (less Cortex (high lymphocytes) and medulla (less

lymphocytes) but consists of a branch of thymic lymphocytes) but consists of a branch of thymic corpuscle cells whose function is unknowncorpuscle cells whose function is unknown

Supplied by blood vessels but less nerve fibersSupplied by blood vessels but less nerve fibers Maximum efficiency during adolescence hood Maximum efficiency during adolescence hood

but becomes small during adulthoodbut becomes small during adulthood Secretes thymosin and its release is dependent Secretes thymosin and its release is dependent

on the demand for T lymphocytes and on the demand for T lymphocytes and antibodies by the bodyantibodies by the body

Functions in preprocessing of T cells and Functions in preprocessing of T cells and development of B cells to plasma cells to development of B cells to plasma cells to produce antibodiesproduce antibodies

Adrenal glandAdrenal gland

Triangular shapedTriangular shaped Located on the left and right kidneysLocated on the left and right kidneys Two endocrine glands that differs in both Two endocrine glands that differs in both

hormone production and target cellshormone production and target cells Inner part - medulla which consists of Inner part - medulla which consists of

secretory cells originating from embryonic secretory cells originating from embryonic ectodermal tissues and ganglia from the ectodermal tissues and ganglia from the symphatetic nervous system branch of symphatetic nervous system branch of the autonomic nervous systemthe autonomic nervous system

Contains two populations of cells that Contains two populations of cells that secretes adrenaline and nor-adrenalinesecretes adrenaline and nor-adrenaline

Outer part - cortex which is bigger and Outer part - cortex which is bigger and produces steroid hormones glucocorticoid, produces steroid hormones glucocorticoid, mineralocorticoid and androgensmineralocorticoid and androgens

Secretion of adrenaline and nor-adrenaline Secretion of adrenaline and nor-adrenaline is dependent on the body’s reaction to is dependent on the body’s reaction to stress stress

Secretion of glucocorticoids and androgens Secretion of glucocorticoids and androgens are controlled by ACTHare controlled by ACTH

Secretion of mineralocorticoid (aldosterone) Secretion of mineralocorticoid (aldosterone) depends on the concentration of water and depends on the concentration of water and ions in the bodyions in the body

GlucocorticoidsGlucocorticoids

FunctionsFunctions

1.1. Stimulates gluconeogenesis (synthesize Stimulates gluconeogenesis (synthesize glucose from liver from non-CHO sources e.g. amino glucose from liver from non-CHO sources e.g. amino acids and fatty acidsacids and fatty acids

2.2. Stimulates glycogenesis (process to produce Stimulates glycogenesis (process to produce glycogen from CHO stores kept in the liver)glycogen from CHO stores kept in the liver)3.3. Anti-inflammatory agent, effective on growth Anti-inflammatory agent, effective on growth and can decrease the effects of physical and and can decrease the effects of physical and emotional stressemotional stress

Glucocorticoid family - cortisol /hydrocortisone, Glucocorticoid family - cortisol /hydrocortisone, corticosterone dan cortisone where cortisol is corticosterone dan cortisone where cortisol is responsible for 95% of glucocorticoid activity responsible for 95% of glucocorticoid activity . .

MineralocorticoidsMineralocorticoids Functions:Functions:

- regulate the concentration of water and ions - regulate the concentration of water and ions e.g; Na and K. e.g; Na and K.

- The main hormone aldosterone functions in - The main hormone aldosterone functions in stimulating Na retention by the kidney and K stimulating Na retention by the kidney and K excretion into urineexcretion into urine

AndrogenAndrogen - secreted in small amounts by sexual secreted in small amounts by sexual

hormoneshormones- Functions: its importance is unknownFunctions: its importance is unknown

  Adrenaline,nor-adrenaline, dopamine = Adrenaline,nor-adrenaline, dopamine =

catecholaminescatecholamines

Adrenaline and nor-adrenaline produces an Adrenaline and nor-adrenaline produces an effect that is similar to stimulation by the effect that is similar to stimulation by the symphatetic nervous systemsymphatetic nervous system

Functions to accelerate the energy Functions to accelerate the energy consumption by body cells and to mobilized consumption by body cells and to mobilized energy stores for body systems utilization energy stores for body systems utilization

Is secreted in body response to stress or flight Is secreted in body response to stress or flight or fight response or fight response

> adrenaline is secreted as compared to nor-> adrenaline is secreted as compared to nor-adrenaline. The half-life is short., only 3 adrenaline. The half-life is short., only 3 minutes then it will be deactivated by hepatic minutes then it will be deactivated by hepatic enzymesenzymes

Adrenaline causes vasoconstriction and Adrenaline causes vasoconstriction and vasodilation of certain blood vessels to vasodilation of certain blood vessels to allocate more blood to the brain and allocate more blood to the brain and musclesmuscles

Digestive process stops, blood pressure > Digestive process stops, blood pressure > heart rate >, clotting time <, respiration heart rate >, clotting time <, respiration rate > and bronchioles dilaterate > and bronchioles dilate

Hepatic enzymes are activated to release Hepatic enzymes are activated to release glucose from glycogen stores (glycolysis) glucose from glycogen stores (glycolysis) for instant energy to cells that needs themfor instant energy to cells that needs them

Adrenaline functions for energy Adrenaline functions for energy consumptionconsumption

Summary of control of Summary of control of Fight or Flight reactionFight or Flight reaction

Adrenaline and nor-adrenaline are secretedAdrenaline and nor-adrenaline are secreted

Vasoconstriction/vasodilation of certain blood vesselsVasoconstriction/vasodilation of certain blood vessels > blood supply to brain and muscles> blood supply to brain and muscles Blood pressure >, Heart rate increases >Blood pressure >, Heart rate increases > Blood clotting time <, Rate of breathing > Glycolysis Blood clotting time <, Rate of breathing > Glycolysis

>, Digestive process stops, Urine output <, Pupils >, Digestive process stops, Urine output <, Pupils dilatedilate

Increase in energy consumptionIncrease in energy consumption Secretion stops after 3 minutes and condition returns Secretion stops after 3 minutes and condition returns

to normalto normal

Running from tsunamiRunning from tsunami

Digestive HormonesDigestive Hormones

GastrinGastrin CholescystokininCholescystokinin SecretinSecretin

• GastrinGastrin is a hormone is a hormone that stimulates that stimulates secretion of gastric acid by the stomach. It is secretion of gastric acid by the stomach. It is released by G cells in the stomach and released by G cells in the stomach and duodenum. duodenum.

• SecretinSecretin is a peptide hormone produced in is a peptide hormone produced in the S cells of the duodenum in the crypts of the S cells of the duodenum in the crypts of Lieberkühn. Its primary effect is to regulate Lieberkühn. Its primary effect is to regulate the pH of the duodenal contents via the the pH of the duodenal contents via the control of gastric acid secretion and buffering control of gastric acid secretion and buffering with bicarbonate. with bicarbonate.

• Cholescystokinin Cholescystokinin is a peptide hormone is a peptide hormone responsible for stimulating the digestion of responsible for stimulating the digestion of fat and protein. Previously called fat and protein. Previously called pancreozyminpancreozymin, this hormone is secreted by , this hormone is secreted by the duodenum, and causes the release of the duodenum, and causes the release of digestive enzymes and bile from the digestive enzymes and bile from the pancreas and gallbladder, respectively. pancreas and gallbladder, respectively.

KidneyKidney

Kidney is basically an excretory organ, Kidney is basically an excretory organ, but it is also an endocrine glandbut it is also an endocrine gland

Secretes three types of hormones:- Secretes three types of hormones:- calcitriol, erythropoeitin and rennin calcitriol, erythropoeitin and rennin

Secretion of calcitriol is dependant on Secretion of calcitriol is dependant on PTH production PTH production

Secretion of erythropoeitin depends on Secretion of erythropoeitin depends on the amount of RBC in the circulationthe amount of RBC in the circulation

Secretion of rennin depends on fluid and Secretion of rennin depends on fluid and ionic concentrationionic concentration

CALCITRIOL,ERITHROPOEITIN AND RENNINCALCITRIOL,ERITHROPOEITIN AND RENNIN

CalcitriolCalcitriol Is synthesize and secreted as a response to Is synthesize and secreted as a response to

PTH secretionPTH secretion Also dependant on vitamin D3 Also dependant on vitamin D3

(cholecalciferol). (cholecalciferol). Functions to stimulate Ca and POFunctions to stimulate Ca and PO44 absorption absorption

from the digestive tractfrom the digestive tract  ErythropoeitinErythropoeitin Stimulates RBC production by > Stimulates RBC production by >

Haemoglobin (Hb) synthesisHaemoglobin (Hb) synthesisand release of RBC from bone marrowand release of RBC from bone marrow

RenninRennin Functions like an enzyme when secreted by Functions like an enzyme when secreted by

cells of the juxtaglomerular apparatus of the cells of the juxtaglomerular apparatus of the kidney into the blood vessels. kidney into the blood vessels.

Rennin changes angiotensinogen (from the Rennin changes angiotensinogen (from the liver) to angiotensin I.  liver) to angiotensin I.  

Angiotensin I changes to angiotensin II by Angiotensin I changes to angiotensin II by angiotensin converting enzymes in the angiotensin converting enzymes in the capillaries of the lungs. Angiotensin II capillaries of the lungs. Angiotensin II functions to:functions to:

1) stimulates aldosterone production from 1) stimulates aldosterone production from the adrenal cortex and ADH secretion from the adrenal cortex and ADH secretion from the post. pituitary the post. pituitary 2) stimulates thirst so we consume more 2) stimulates thirst so we consume more fluids to increase blood volumefluids to increase blood volume3) triggers arteriole contraction so that 3) triggers arteriole contraction so that blood volume increases and this effect is blood volume increases and this effect is 4-8 X > effects by noradrenaline 4-8 X > effects by noradrenaline

The rennin-angiotensin I-angiotensin The rennin-angiotensin I-angiotensin II system influences blood pressure II system influences blood pressure and volume, salt intake and salt-fluid and volume, salt intake and salt-fluid balance balance

Rennin is secreted when there is a Rennin is secreted when there is a symphatetic stimulation and < blood symphatetic stimulation and < blood flow to the kidneys due to < blood flow to the kidneys due to < blood volume, blood pressure or bothvolume, blood pressure or both

HeartHeart

Basically the heart is the most important Basically the heart is the most important organ in the circulatory systemorgan in the circulatory system

The heart however also contains secretory The heart however also contains secretory cells located at the atrium that cells located at the atrium that synthesize, store and secretes a peptide synthesize, store and secretes a peptide hormone called atrial natriuretic peptide hormone called atrial natriuretic peptide (ANP).(ANP).

ANP secretion depends on the salt ANP secretion depends on the salt concentration in the bodyconcentration in the body

ATRIAL NATRIURETIC PEPTIDEATRIAL NATRIURETIC PEPTIDE

Is secreted continuously but in a small Is secreted continuously but in a small amount in the circulation amount in the circulation

The secretion when > salt in the The secretion when > salt in the body, blood pressure > which body, blood pressure > which stimulate stretch receptors in the stimulate stretch receptors in the atrium or when blood pressure > atrium or when blood pressure > significantlysignificantly

Target cells are the blood vessels, Target cells are the blood vessels, kidney and adrenal glandkidney and adrenal gland

Functions :Functions :   1) stimulates Na and air excretion by 1) stimulates Na and air excretion by

kidneyskidneys2) inhibit rennin release and the 2) inhibit rennin release and the secretion of hormones (ADH and secretion of hormones (ADH and aldosterone) involve in water retentionaldosterone) involve in water retention3)3) < thirst and inhibit the action of < thirst and inhibit the action of angiotensin II or nor-adrenaline on angiotensin II or nor-adrenaline on arterioles. The relaxation of blood arterioles. The relaxation of blood vessels will help to < blood pressure vessels will help to < blood pressure and cardiac muscles stretching on the and cardiac muscles stretching on the atriaatria

Pineal glandPineal gland A small granule located at the at A small granule located at the at

the diencenphalon at the inner the diencenphalon at the inner part of the cerebral hemisphere on part of the cerebral hemisphere on the posterior part of the third the posterior part of the third ventricle ventricle

Contains neuron, glial cells and Contains neuron, glial cells and secretory cells called pinocytessecretory cells called pinocytes

Synthesize the hormone melatonin Synthesize the hormone melatonin from serotonin molecules which is from serotonin molecules which is a neurotransmitter. a neurotransmitter.

Melatonin secretion is dependant Melatonin secretion is dependant on light availabilityon light availability

How? This is because the How? This is because the collateral nerve from the collateral nerve from the vision pathway enters the vision pathway enters the pineal gland and this pineal gland and this influence the melatonin influence the melatonin production rate production rate

Melatonin is secreted more Melatonin is secreted more at night as compared to at night as compared to daytimedaytime

MelatoninMelatonin

Is secreted at a constant rate every nightIs secreted at a constant rate every night Production is inhibited by lightProduction is inhibited by light < secretion of melatonin causes drowsiness < secretion of melatonin causes drowsiness

because the sleep cycle is disturbedbecause the sleep cycle is disturbed Important to maintain biological rhythm and Important to maintain biological rhythm and

light-dark cycle light-dark cycle In mammals, melatonin slows sperm, ovum In mammals, melatonin slows sperm, ovum

and reproductive organ maturity by < rate of and reproductive organ maturity by < rate of Gn-RH secretionGn-RH secretion

Melatonin may also slow down human sexual Melatonin may also slow down human sexual maturity (levels of melatonin in the blood falls maturity (levels of melatonin in the blood falls at puberty. If there is a tumour at the pineal at puberty. If there is a tumour at the pineal gland, loss of melatonin will cause premature gland, loss of melatonin will cause premature puberty to childrenpuberty to children

An important antioxidant that protects CNS An important antioxidant that protects CNS from free radicals NO or Hfrom free radicals NO or H22002 2 produced by produced by active nervous tissuesactive nervous tissues

Activity of pineal gland is cyclic i.e., plays a role Activity of pineal gland is cyclic i.e., plays a role in the circadian rhythm (daily changes in in the circadian rhythm (daily changes in physiological process that follows the same physiological process that follows the same pattern)pattern)

> melatonin secretion during the dark may be > melatonin secretion during the dark may be the primary cause for a condition called the primary cause for a condition called ‘‘seasonal affective disorder (SAD)’.seasonal affective disorder (SAD)’.

SAD = changes to behavior, nutritional intake SAD = changes to behavior, nutritional intake and sleep patterns occurring to people living at and sleep patterns occurring to people living at high altitudes during the winter when amount of high altitudes during the winter when amount of light is shorterlight is shorter

Important in the digestive processImportant in the digestive process Elongated and fleshy and about 12 – 15 Elongated and fleshy and about 12 – 15

cm longcm long Located posterior to the stomach Located posterior to the stomach An exocrine and endocrine organAn exocrine and endocrine organ The exocrine component is involved in the The exocrine component is involved in the

digestive process digestive process The endocrine part is located at the Islets The endocrine part is located at the Islets

of Langerhans which is about 200,000 to 2 of Langerhans which is about 200,000 to 2 million islets in an adult pancreasmillion islets in an adult pancreas

PancreasPancreas

The islets contains alpha cells (The islets contains alpha cells (glucagon)glucagon), , beta cells (beta cells (insulin)insulin), delta cells , delta cells ((somatostatin)somatostatin) and F cells (p and F cells (pancreatic ancreatic polypeptide)polypeptide)

The secretion of glucagon and insulin The secretion of glucagon and insulin depends on glucose concentration in the depends on glucose concentration in the bloodblood

Secretion of somatostatin depends on GHSecretion of somatostatin depends on GH Secretion of pancreatic polypeptide Secretion of pancreatic polypeptide

depends on the release of digestive depends on the release of digestive enzymes from the pancreasenzymes from the pancreas

GLUCAGON GLUCAGON 

Peptide hormone ( hyperglycemic hormone).Peptide hormone ( hyperglycemic hormone). Function - stimulate glycogenolysis (stimulate the Function - stimulate glycogenolysis (stimulate the

liver to convert glycogen to glucose whenever liver to convert glycogen to glucose whenever hypoglycemia occurshypoglycemia occurs

Also stimulates gluconeogenesis, lypogenolysis Also stimulates gluconeogenesis, lypogenolysis (release of fatty acids and glycerol from adipose (release of fatty acids and glycerol from adipose tissues) and > cAMP concentration from ATP in tissues) and > cAMP concentration from ATP in hepatocyes hepatocyes 

INSULIN INSULIN

Peptide hormones (hypoglycemic hormone)Peptide hormones (hypoglycemic hormone) The first hormone that has its full chemical The first hormone that has its full chemical

structure identified by Frederick Sanger in 1955. structure identified by Frederick Sanger in 1955. Function: > glucose uptake into cells, > conversion Function: > glucose uptake into cells, > conversion

of glucose to glycogen (glycogenesis) to be stored of glucose to glycogen (glycogenesis) to be stored in the liver  in the liver  

> glucose transport into cells which will > > glucose transport into cells which will > CHO metabolism and < blood glucose CHO metabolism and < blood glucose concentration (hypoglycemic)concentration (hypoglycemic)

> amino acid transport into cells to > > amino acid transport into cells to > protein synthesis protein synthesis

> conversion of glucose to fatty acids > conversion of glucose to fatty acids (lypogenesis). (lypogenesis).

Act antagonistically with glucagon because Act antagonistically with glucagon because it < glucogenolysis and gluconeogenesis.it < glucogenolysis and gluconeogenesis.

If > insulin secreted, hypoglycemia occurs If > insulin secreted, hypoglycemia occurs If < insulin secreted, diabetes mellitus occur If < insulin secreted, diabetes mellitus occur

and will cause hyperglycemia and excess and will cause hyperglycemia and excess glucose will be excreted by the kidneys into glucose will be excreted by the kidneys into urineurine

  

Why do diabetics have to take injectable Why do diabetics have to take injectable insulin rather than oral insulin? This is insulin rather than oral insulin? This is because insulin molecules are so small and because insulin molecules are so small and if taken orally, will be destroyed by the if taken orally, will be destroyed by the gastric juices in the stomach.gastric juices in the stomach.

SOMASTOSTATINSOMASTOSTATIN A GH-IH like hormone that can inhibit insulin A GH-IH like hormone that can inhibit insulin

and glucagon secretionand glucagon secretion

PANCREATIC POLYPEPTIDEPANCREATIC POLYPEPTIDE Regulate the secretion of digestive Regulate the secretion of digestive

enzymes from the pancreasenzymes from the pancreas

Part of the male reproductive tractPart of the male reproductive tract Produces testosterone from the Produces testosterone from the

interstitial cells of Leydig and inhibin interstitial cells of Leydig and inhibin from Sertoli cellsfrom Sertoli cells

TestisTestis

TESTOSTERONETESTOSTERONE

Functions:Functions: Stimulate sperm production together with Stimulate sperm production together with

FSH and LH FSH and LH Growth, development and maintanance of Growth, development and maintanance of

male sexual organs male sexual organs Stimulate development and maintains male Stimulate development and maintains male

sexual libido sexual libido Responsible for development of male Responsible for development of male

secondary sexual characteristics incl. voice secondary sexual characteristics incl. voice deepening, body hair growth, muscle mass deepening, body hair growth, muscle mass and othersand others

Production of testosterone depends on the Production of testosterone depends on the testosterone levels in bloodtestosterone levels in blood

If increase, will send negative feedback If increase, will send negative feedback mechanism to pit. ant. to inhibit LH releasemechanism to pit. ant. to inhibit LH release

INHIBININHIBIN Function:Function: Helps in sperm production Helps in sperm production If amount of sperm > 20 million cells/ml, inhibin If amount of sperm > 20 million cells/ml, inhibin

will send a negative feedback mechanism to the will send a negative feedback mechanism to the ant pit to inhibit FSH releaseant pit to inhibit FSH release

  

Part of female reproductive systemPart of female reproductive system Produces estrogene (follicles), Produces estrogene (follicles),

progesterone (corpus luteum), progesterone (corpus luteum), inhibin (follicle), relaxin (corpus inhibin (follicle), relaxin (corpus luteum) during pregnancyluteum) during pregnancy

Uterus Uterus – produces prostaglandin F – produces prostaglandin F 22

OvaryOvary

ESTROGENEESTROGENE  

Function: Function: Regulate menstrual cycleRegulate menstrual cycle Development of the mammary glandsDevelopment of the mammary glands Development of female secondary sexual Development of female secondary sexual

characteristics (enlargement of breasts, > characteristics (enlargement of breasts, > adipose tissue at the buttock, growth of body adipose tissue at the buttock, growth of body hairs, and maintanance of female sexual organs). hairs, and maintanance of female sexual organs).

Hormone that stimualates sexual desire in Hormone that stimualates sexual desire in womenwomen

PROGESTERONEPROGESTERONE

Function:Function: Maintains pregnancyMaintains pregnancy Regulate menstrual cycleRegulate menstrual cycle Development of mammary glands and Development of mammary glands and

placental formation during pregnancyplacental formation during pregnancy Pregnancy hormonePregnancy hormone

RELAXINRELAXIN

Function:Function: Important during parturition Important during parturition Softens cervix by causing ligament dilation at Softens cervix by causing ligament dilation at

the symphisis pubis to facilitate deliverythe symphisis pubis to facilitate delivery Helps in development of mammary glands Helps in development of mammary glands

during pregnancy during pregnancy During early pregnancy, secretion of relaxin During early pregnancy, secretion of relaxin

depends on LH influencedepends on LH influence At the end of pregnancy, relaxin is secreted At the end of pregnancy, relaxin is secreted

due to the influence of human chorionic due to the influence of human chorionic gonadotrophin released by the uterus. Relaxin gonadotrophin released by the uterus. Relaxin secretion stops after parturitionsecretion stops after parturition

PROSTAGLANDIN F2PROSTAGLANDIN F2

Function:Function: Kills corpus luteum (luteolytic) when Kills corpus luteum (luteolytic) when

no fertilization occurs and no no fertilization occurs and no embryonic implantation embryonic implantation

Can cause eruption of spiral arteries Can cause eruption of spiral arteries in the uterus and endometrium to in the uterus and endometrium to contract causing menstrual crampscontract causing menstrual cramps

Can erode sperm plasma membrane Can erode sperm plasma membrane causing capacitation during sperm causing capacitation during sperm transport in the female reproductive transport in the female reproductive tracttract