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Endocrine System

By

Shahzad Bashir

RN, BScN

NMC (ION)

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ObjectivesBy the end of this lecture, you will be able to:

�Define endocrine system.

�Identify endocrine glands and endocrine tissues present in the body.

�Discuss types of hormones, target cell, target organ.

�Briefly discuss mechanism of action of hormone(proteins and steroids).

�Discuss the location and structure of pituitary gland.

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Objectives

�Discuss the role of hypothalamic hormones in the regulation of pituitary gland secretions.

�Discuss the function of hormones secreted by anterior and posterior pituitary gland.

�Briefly discuss the structure, function and hormones of the following glands

�Thyroid, parathyroid, pineal,adrenal and pancreas.

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Endocrine System

It is system of ductless gland which pour their secretions directly into the bloodstream.

Consists of endocrine glands that release chemical messengers called hormones.

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FUNCTIONS OF THE FUNCTIONS OF THE ENDOCRINE SYSTEMENDOCRINE SYSTEM

Regulation of effectors to maintain homeostasis.

Water balanceWater balance

Uterine contractions & milk releaseUterine contractions & milk release

Growth, metabolism, & tissue maturationGrowth, metabolism, & tissue maturation

Ion regulationIon regulation

Heart rate & blood pressure regulationHeart rate & blood pressure regulation

Blood glucose controlBlood glucose control

Immune system regulationImmune system regulation

Reproductive functions controlReproductive functions control7/6/2012 6

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HomeostasisThe word homeostasis means “the maintenance

of stable internal conditions in an organism”.

Example: Blood sugar is too high, and the pancreas makes more insulin to reduce the level of sugar. Blood sugar goes down. When it is

low enough, the production ceases. Insulin will be produced again when blood sugar again

increases.

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HORMONESComes from the greek word hormaein whichmeans “ to excite”Mediator molecules released by the glands of the endocrine system

ENDOCRINE GLANDSProduce hormones thatare released into thecirculatory system

and travel some distancewhere they act on target

tissues to produce aresponse

“ductless glands”

EXOCRINE GLANDSSecrete products intoducts (sweat glands,sebaceous glands, mucous & digestive

glands)

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Receptors—protein molecules that trigger specific physiologic changes in a target cell in response to hormonal stimulation

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Endocrine Glands

1 Pituitary gland

1 thyroid gland

4 parathyroid gland

2 adrenal(suprarenal) glands

The pancreatic islets(islets of langerhans)

1 pineal gland

1 thymus gland

2 ovaries in female

2 testes in male7/6/2012 10

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THE PITUITARY & THE PITUITARY & HYPOTHALAMUSHYPOTHALAMUS

HYPOTHALAMUSHYPOTHALAMUS

Autonomic nervous system & endocrine control Autonomic nervous system & endocrine control center of the braincenter of the brain

Inferior to the thalamusInferior to the thalamus

Controls the pituitary gland in 2 ways:Controls the pituitary gland in 2 ways:

Produce RELEASING HORMONESProduce RELEASING HORMONES

Controls the secretion of hormones in the posterior Controls the secretion of hormones in the posterior pituitarypituitary

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PITUITARY GLANDPITUITARY GLAND

Hypophysis & called “master gland”Hypophysis & called “master gland”

Located in ventral surface of brain within skullLocated in ventral surface of brain within skull

Divided into anterior (adenohypophysis) & posterior Divided into anterior (adenohypophysis) & posterior pituitary (neurohypophysis)pituitary (neurohypophysis)

Anterior pituitaryAnterior pituitary: made up of epithelial cells derived : made up of epithelial cells derived from embryonic oral cavityfrom embryonic oral cavity

Posterior pituitaryPosterior pituitary: extension of the brain and made : extension of the brain and made up of nerve cellsup of nerve cells

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Secretions from anterior pituitary Secretions from anterior pituitary are controlled by hypothalamicare controlled by hypothalamic--releasing hormone (hypothalamicreleasing hormone (hypothalamic--pituitary portal system) pituitary portal system) Secretions from posterior pituitary Secretions from posterior pituitary controlled by nerve impulses that controlled by nerve impulses that pass through infundibulumpass through infundibulum

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Hormones released from Hormones released from anterior pituitaryanterior pituitary

growth hormone (GH)growth hormone (GH)

thyroidthyroid--stimulating hormone (TSH)stimulating hormone (TSH)

adrenocorticotropic hormone (ACTH)adrenocorticotropic hormone (ACTH)

luteinizing hormone (LH)luteinizing hormone (LH)

folliclefollicle--stimulating hormone (FSH)stimulating hormone (FSH)

prolactinprolactin

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Hormones released from Hormones released from posterior pituitaryposterior pituitary

antidiuretic hormone (ADH) and oxytocinantidiuretic hormone (ADH) and oxytocin

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HORMONESHORMONESGH GH –– promotes growth of bone, muscle & other promotes growth of bone, muscle & other

tissues; function as insulin antagonist vital in tissues; function as insulin antagonist vital in maintaining homeostasis of blood glucose levelmaintaining homeostasis of blood glucose level

Prolactin Prolactin –– promotes development of breast, promotes development of breast, anticipating milk secretion (during pregnancy), anticipating milk secretion (during pregnancy), stimulates mother’s mammary gland for milkstimulates mother’s mammary gland for milk

TSH TSH -- growth & development of thyroid gland; growth & development of thyroid gland; cause thyroid gland to release hormonescause thyroid gland to release hormones

ACTH ACTH –– increase secretion of cortisol from adrenal increase secretion of cortisol from adrenal

cortex; increase skin pigmentationcortex; increase skin pigmentation

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FSH FSH –– stimulates development of follicles in stimulates development of follicles in ovaries & sperm cellsovaries & sperm cellsLH LH –– stimulates the formation & activity of corpus stimulates the formation & activity of corpus luteum (secretes progesterone & estrogen) in luteum (secretes progesterone & estrogen) in ovary, stimulates interstitial cells in the testes to ovary, stimulates interstitial cells in the testes to develop & secrete testosteronedevelop & secrete testosteroneOxytocin Oxytocin –– stimulates contraction of uterine stimulates contraction of uterine muscles and causes milk ejectionmuscles and causes milk ejectionAntidiuretic hormone Antidiuretic hormone –– helps body conserve helps body conserve

water, prevents formationwater, prevents formation of large volume ofof large volume of

urine, maintains water balance in the bodyurine, maintains water balance in the body7/6/2012 18

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PINEAL GLANDPINEAL GLAND

Small gland attached to the roof of 3Small gland attached to the roof of 3rdrd ventricleventricle

Part of epithalamus positioned between 2 Part of epithalamus positioned between 2 superior colliculi (weighs .1superior colliculi (weighs .1--.2 grams) .2 grams)

Consists of secretory cells called pinealocytes, Consists of secretory cells called pinealocytes, neuroglia, and scattered postganglionic neuroglia, and scattered postganglionic

sympathetic fiberssympathetic fibers

Secretes melatonin which contributes to the Secretes melatonin which contributes to the setting the body’s biological clock (patterns of setting the body’s biological clock (patterns of

eating, sleeping, reproduction & behavior)eating, sleeping, reproduction & behavior)7/6/2012 21

HORMONE OF THE PINEAL BODY

MELATONIN

(AT LEAST THE

HYPOTHALAMUS)

Inhibits secretion of

gonadotropin-releasing hormone

thereby inhibiting reproduction

Induce sleep

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THYROID GLANDTHYROID GLAND

Made up of 2 large lateral lobes & a narrow Made up of 2 large lateral lobes & a narrow connecting isthmus (weight: 30 grams)connecting isthmus (weight: 30 grams)

Located in the neck, on the anterior & Located in the neck, on the anterior & lateral surface of trachea, just below the lateral surface of trachea, just below the

larynxlarynx

Thyroid hormone: regulate metabolic rate Thyroid hormone: regulate metabolic rate of all cells & cell growth & tissue of all cells & cell growth & tissue

differentiation; have a “general” target (T3 differentiation; have a “general” target (T3 & T4); produced by follicular cells& T4); produced by follicular cells7/6/2012 23

Triiodothyronine (T3) Triiodothyronine (T3) –– principal thyroid principal thyroid hormone; contains 3 iodine atoms; binds hormone; contains 3 iodine atoms; binds efficiently to nuclear receptors in target cellsefficiently to nuclear receptors in target cellsTetraiodothyronine (T4) or thyroxine Tetraiodothyronine (T4) or thyroxine –– 20 times 20 times more abundant than T3; contains 4 iodine more abundant than T3; contains 4 iodine atomsatomsCalcitonin Calcitonin –– produce by the thyroid gland in the produce by the thyroid gland in the parafollicular cells; influences the processing of parafollicular cells; influences the processing of calcium in bone cells by decreasing blood calcium in bone cells by decreasing blood calcium level & promote conservation of hard calcium level & promote conservation of hard bone matrixbone matrixParathyroid hormone Parathyroid hormone –– antagonist to calcitonin antagonist to calcitonin to maintain calcium homeostasisto maintain calcium homeostasis7/6/2012 24

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HORMONES OF THE THYROID GLANDTRIIODOTHYRONINE(T3) =increases rate of metabolism

TETRAIODOTHYRONINE THYROXINE(T4)= increases rate of

metabolism

CALCITONIN=Increase calcium storage in bone

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PARATHYROID GLANDPARATHYROID GLANDSmall, round masses of tissue attached to the posterior Small, round masses of tissue attached to the posterior

surface of lateral lobes of thyroid glandsurface of lateral lobes of thyroid gland

PTH:PTH:

Increases number & activity of osteoclastsIncreases number & activity of osteoclasts

Results in elevated bone resorption which releases Results in elevated bone resorption which releases ionic calcium & phosphates into the bloodionic calcium & phosphates into the blood

Produces changes in the kidneys: increase rate at Produces changes in the kidneys: increase rate at which it removes calcium and magnesium from urine which it removes calcium and magnesium from urine

& returns it to the blood, inhibits reabsorption of & returns it to the blood, inhibits reabsorption of phosphates filtered by kidneys (more is excreted in phosphates filtered by kidneys (more is excreted in

urine), promote formation of hormone calcitriol urine), promote formation of hormone calcitriol (active form of vit D) which increases rate of calcium, (active form of vit D) which increases rate of calcium,

phosphates & magnesium absorption from GI to phosphates & magnesium absorption from GI to bloodblood

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HORMONE OF THE PARATHYROID

GLAND

PARATHYROID HORMONE

(BONE TISSUE & KIDNEY)

Increase calcium removal from storage in bone

Produces active form of vitamin D in kidneys

Increase absorption of calcium by intestines

Increase blood calcium level

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ADRENAL GLANDSADRENAL GLANDS

Located on top of kidneys, fitting like capsLocated on top of kidneys, fitting like caps

Made up of 2 portions: adrenal cortex (endocrine Made up of 2 portions: adrenal cortex (endocrine tissue) and adrenal medulla (neurosecretory tissue) and adrenal medulla (neurosecretory

tissue)tissue)

33--5 cm height, 25 cm height, 2--3 cm width, 3.53 cm width, 3.5--5 grams5 grams

Adrenal cortex: large periphery (80Adrenal cortex: large periphery (80--90% of the 90% of the gland by weight)gland by weight)

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Adrenal cortex

�Three zones:

Zona glomerulosa (outermost zone)—produces mineralocorticoids, primarily aldosterone

Zona fasciculata (middle and largest zone)—produces the glucocorticoids cortisol

(hydrocortisone), cortisone, and corticosterone and small amounts of androgen and estrogen

Zona reticularis (innermost zone)—produces mainly glucocorticoids and some sex hormones

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Glucocorticoids (cortisol) Glucocorticoids (cortisol) –– reduce reduce inflammation & break down fat & protein inflammation & break down fat & protein making them available as energy sources to making them available as energy sources to other tissuesother tissuesMineralocorticoids (aldosterone) Mineralocorticoids (aldosterone) –– help help regulate sodium & potassium levels & water regulate sodium & potassium levels & water volume in the bodyvolume in the bodyAdrenal androgens Adrenal androgens –– male sex hormonemale sex hormone

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Adrenal MedullaAdrenal Medulla

Situated directly a top each kidney and stimulated by Situated directly a top each kidney and stimulated by the sympathetic nervous systemthe sympathetic nervous system

Secretes the catecholaminesSecretes the catecholamines

EpinephrineEpinephrine: elicits a fight or flight response: elicits a fight or flight response

Increase H.R. and B.P.Increase H.R. and B.P.

Increase respirationIncrease respiration

Increase metabolic rateIncrease metabolic rate

Increase glycogenolysisIncrease glycogenolysis

VasodilationVasodilation

NorepinephrineNorepinephrine

House keeping systemHouse keeping system7/6/2012 33 7/6/2012 34

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PANCREASPANCREASElongated gland (5Elongated gland (5--6 inches long, weight: 500 6 inches long, weight: 500

grams); located posterior & inferior to the grams); located posterior & inferior to the stomachstomach

Tissue composed of endocrine & exocrine tissuesTissue composed of endocrine & exocrine tissues

Pancreatic islets (islets of Langerhans) Pancreatic islets (islets of Langerhans) --scattered tiny island of cells (2scattered tiny island of cells (2--3% of total mass)3% of total mass)

HormoneHormone--producing islets are surrounded by cells producing islets are surrounded by cells called ACINI (secretes a serous fluid containing called ACINI (secretes a serous fluid containing

digestive enzymes into ducts that drain into small digestive enzymes into ducts that drain into small intestineintestine

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4 hormone4 hormone--secreting cell typessecreting cell types::

ALPHA or A cellsALPHA or A cells –– 20% of islet cells secreting 20% of islet cells secreting GLUCAGON (raises blood sugar level)GLUCAGON (raises blood sugar level)BETA or B cellsBETA or B cells –– 70% of islet cells secreting 70% of islet cells secreting INSULIN (lowers blood sugar level)INSULIN (lowers blood sugar level)DELTA or D cellsDELTA or D cells –– 50% of islet cells secreting 50% of islet cells secreting SOMASTATIN (inhibit both insulin & glucagon SOMASTATIN (inhibit both insulin & glucagon release; slows absorption of nutrients from the GI release; slows absorption of nutrients from the GI tracttractF cellsF cells –– secrete PANCREATIC POLYPEPTIDE secrete PANCREATIC POLYPEPTIDE (inhibits somastatin secretion, gallbladder (inhibits somastatin secretion, gallbladder contraction & secretion of digestive enzymes by contraction & secretion of digestive enzymes by the pancreas)the pancreas)

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HORMONES OF THE PANCREATIC

ISLETS

GLUCAGON

(GENERAL)Promotes movement of glucose from storage and into the blood

INSULIN

(GENERAL)

Promotes movement of glucose out of the blood and into the cells7/6/2012 39

REPRODUCTIVE ORGANSREPRODUCTIVE ORGANS

FEMALEFEMALEOVARIES OVARIES –– paired oval female gonads located paired oval female gonads located

in pelvic cavityin pelvic cavity

Produces estrogen & progesterone Produces estrogen & progesterone –– regulate regulate female reproductive cycle, maintain pregnancy female reproductive cycle, maintain pregnancy

& prepare mammary glands for lactation& prepare mammary glands for lactation

Produce inhibin (inhibits secretion of FSH) and Produce inhibin (inhibits secretion of FSH) and relaxin (increases flexibility of pubic symphysis relaxin (increases flexibility of pubic symphysis during pregnancy & dilate uterine cervix during during pregnancy & dilate uterine cervix during

labor)labor)7/6/2012 40

MALEMALE

TESTES TESTES –– 2 oval gonads 2 oval gonads

Produce testosterone that regulates production ofProduce testosterone that regulates production of

sperm & stimulates development & sperm & stimulates development &

maintenance of masculine secondary sex maintenance of masculine secondary sex

characteristicscharacteristics

Produce inhibin (inhibits secretion of FSH)Produce inhibin (inhibits secretion of FSH)7/6/2012 41

HORMONES OF THE REPRODUCTIVE ORGANS

TESTES OVARIESUTERUS &

OVARIES

TESTOSTERONE ESTROGEN &

PROGESTERONEPROSTAGLANDINS

(MOST TISSUES)

Sperm cell production,

maintain functional repro

organs

(MOST TISSUES)

Mediate inflammatory

responses; increase

uterine contractions

(MOST TISSUES)

Uterine and mammary

gland development &

function, etc.

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THYMUSTHYMUS

2 lobes, located in mediastinum, between 2 lobes, located in mediastinum, between sternum and large blood vessels above the heart; sternum and large blood vessels above the heart;

site of T cell maturationsite of T cell maturation

Secretes hormones related to immunitySecretes hormones related to immunity

Each lobule consists of deep straining outer Each lobule consists of deep straining outer cortexcortex and lighter staining central and lighter staining central medullamedulla

Cortex: Cortex: lymphocytes, reticular epithelial cells & lymphocytes, reticular epithelial cells & macrophagesmacrophages

Medulla: Medulla: mostly reticular epithelial cells (produce mostly reticular epithelial cells (produce thymic hormones) & scattered lymphocytesthymic hormones) & scattered lymphocytes7/6/2012 43

HORMONE OF THE THYMUS GLAND

THYMOSIN

(IMMUNE TISSUES)

Promotes immune system

development and function

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OTHER ORGANS THAT CONTAIN OTHER ORGANS THAT CONTAIN ENDOCRINE CELLSENDOCRINE CELLS

GASTROINTESTINAL TRACT: gastrin, secretin, GASTROINTESTINAL TRACT: gastrin, secretin, cholecystokinincholecystokinin

PLACENTA: human chorionic gonadotropin, PLACENTA: human chorionic gonadotropin, estrogen/progesterone, human chorionic estrogen/progesterone, human chorionic

somatomammotropinsomatomammotropin

KIDNEYS: erythropoietin (EPO), calcitriolKIDNEYS: erythropoietin (EPO), calcitriol

HEART: atrial nutriuretic peptide (ANP)HEART: atrial nutriuretic peptide (ANP)

ADIPOSE TISSUE: leptinADIPOSE TISSUE: leptin

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Feedback Mechanisms

Control of hormone secretions is accomplished by an internal control system.

In most instances, a feedback mechanism is employed.

The majority of feedback loops work as a negative feedback.

In negative feedback, the endocrine gland has a natural tendency to over-secrete its

hormone.

The hormone then stimulates the target tissue to perform a function 7/6/2012 46

Thus, the important factor is not the rate of secretion of the hormone but the rate that the target function is performed.When the target organ’s activity rises to an appropriate level, feedback is released to the endocrine gland to

slow further secretion of the hormone.For example, the pituitary gland (endocrine gland) secretes thyroid-stimulating hormone, which acts on the target organ, the thyroid gland, to stimulate production of the thyroid hormones T3 and T4. The pituitary then monitors the circulating levels of

thyroid hormones. 7/6/2012 47

When these levels are deemed by the pituitary to have reached appropriate levels, the release of TSH by the pituitary is curtailed. If the target organ (in this case the thyroid gland) were not to be able to produce adequate amounts of thyroid hormones, a healthy pituitary would secrete more and more TSH until the

thyroid gland responded.7/6/2012 48

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ENDOCRINE CONDITIONS

HYPERSECRETION

� ACROMEGALY

� ALDOSTERONISM

� CUSHING SYNDROME

� GIGANTISM

� HYPERPARATHYROIDISM

� GRAVES DISEASE

HYPOSECRETION

� ADDISON DISEASE

� CRETINISM

� DIABETES INSIPIDUS

� TYPE 1 DIABETES

MELLITUS

� OSTEOPOROSIS

� PITUITARY DWARFISM

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CONDITIONCONDITION HORMONEHORMONE DESCRIPTIONDESCRIPTION

AcromegalyAcromegaly GHGH Elongation of facial & Elongation of facial & extremity bonesextremity bones

AldosteronisAldosteronismm

AldosteroneAldosterone Sodium retention and Sodium retention and potassium losspotassium loss

Cushing Cushing SyndromeSyndrome

GlucocorticoiGlucocorticoidd

Rounded “moon” face, Rounded “moon” face, muscular atrophy, muscular atrophy, edema etc.edema etc.

GigantismGigantism GHGH Extreme skeletal sizeExtreme skeletal size

HyperHyper--

parathyroidiparathyroidismsm

PTHPTH Increase reabsorption Increase reabsorption of Ca from bone tissues of Ca from bone tissues & kidneys& kidneys

Graves Graves DiseaseDisease

Thyroid Thyroid hormonehormone

Hyperthyroidism, Hyperthyroidism, exophthalmosexophthalmos

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CONDITIONCONDITION HORMONEHORMONE DESCRIPTIONDESCRIPTION

Addison Addison DiseaseDisease

Adrenal Adrenal cortical cortical

hormonehormone

Weakness, Weakness, anorexia, weight anorexia, weight loss, irritability etcloss, irritability etc

CretinismCretinism Thyroid Thyroid hormonehormone

Dwarfism, MR, Dwarfism, MR, facial puffiness, dry facial puffiness, dry skin etc.skin etc.

Diabetes Diabetes InsipidusInsipidus

ADHADH Extreme polyuria & Extreme polyuria & polydipsiapolydipsia

Type 1 Type 1 Diabetes Diabetes MellitusMellitus

InsulinInsulin Polydipsia, Polydipsia, polyuria, polyuria, overeating, weight overeating, weight lossloss

OsteoporosisOsteoporosis EstrogenEstrogen Bone disorder, loss Bone disorder, loss of minerals & of minerals & collagencollagen

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