The thyroglossal tract arises form a median bud in the pharynx, it passes from foramen caecum at junction of anterior 2/3 and posterior 1/3 of the tongue and descend toward the root of the neck forming two lobes linked by isthmus. The fourth or fifth pharyngeal pouch gives rise to parafollicular cells ( C cell) which amalgamate with the lobes of the gland.

It is composed of 2 lobes linked by isthmus lying over the second, third and fourth tracheal rings. WT is about 20 to 25 gm. its heavier in female, its just visible in normal person.

The functioning unit is the lobule, which composed of follicles lined by cubical epithelium.

The T.G secretes 3 hormones: Thyroxin T4 Tri-iodothyronine T3 Calcitonin (regulates Ca and ph. Levels) An adequate supply of iodine is required

for the synthesis of these hormones (100 microgram). The most common source is table salt and fish.

Functions of thyroid Hormones1- Growth and development2- Carbohydrate, protein and fat metabolism3- Vitamin metabolism4- Basal metabolic rate5- Effect on the cardiovascular system6- Increase oxygen consumption by the tissue7- Increase oxygen release from Hb8- Effect on muscle function9- Increase oxidative phosphorylation10- Induce hyperglycemia.11- Augmentation of adrenalin and

noradrenalin function

HYPOTHALAMUS

Thyrotropin releasing hormone (TRH)

PITUITARY

Thyroid stimulating hormone (TSH)

THYROID GLAND

Secretes T4 (main hormone) and T3.

•Metabolic demands •Drugs• Infection• Surgery•Trauma •Low temperature•Pit. disorders•Age•stress •Sleep

-VE FEEDBACK MECHANISM

As blood concentrations of thyroid hormones increase, they inhibit both TSH and TRH, leading to "shutdown" of thyroid epithelial cells. Later, when blood levels of thyroid hormone have decayed, the negative feedback signal fades, and the system wakes up again.

T3 is four times more powerful than T4 T3 less adherent to the binding protein.(98%

in comparison with 99.9% for T4) Half life of T3 is 3 days (8 to14 days for T4). All T4 change to T3 at the cellular level. The normal thyroid gland produces about 80%

T4 and about 20% T3.Every cell in the body depends upon thyroid

hormones for regulation of their metabolism.

A- Hormone measurement1- Total T3 1.2 to 2.8 nmol\L2- Total T4 150 nmol\L3- TSH 0.5 to 5 mU\LB- Measurement of thyroid-pituitary-hypothalamic axis

(TSH stimulation test, TRH stimulation test).

C-Thyroid scanning: use of RAI131 then the gland is scanned to see its uptake.

D- Biopsy (FNA ,Core biopsy, Incisional biopsy, excisional biopsy.

E-Imaging study1-Ultrasound2-MRI3- CT scan.

Due to either hypo- or hyper function of gland

They are the second most common endocrine disorder – mostly in woman

Congenital (Agenesis / Ectopic as lingual, supra or infrahyoid , mediastinal ) / persistent thyroglossal duct result in cyst or fistula

Hypofunction (hypothyroidism)

Hyperfunction (thyrotoxicosis)

Thyroiditis.

Thyroid gland neoplasm.

The enlargement may be diffuse, nodular, singular, functional or non-functional.

Hyperthyroidism

Hypothyroidism

Euthyroid (normal levels)

Failure of thyroid gland to produce adequate level of H. It is either1- Congenital

2-Acquired ( primary or secondary)

In adults called myxedemaIn children called cretinism

A- Idiopathic (spontaneous)B- Autoimmune C- ThyroiditisC- Surgery (partial, sub-total or total )D- Radioactive iodineE- Drugs (thiocyanate, propyl-thiouracil -PTU, lithium,

phenylbutazone.F- Post- thyroiditis (Hashimotos)G- Iodine deficiency H- Secondary to pituitary gland failure.

Treatment is replacement therapy (Levothyroxine)

Hypothyroidism

The commonest causes are Primary hyperthyroidism –toxic diffuse goiter - (Graves disease) Toxic nodular goiter Toxic solitary nodule Hashimotos thyroiditis Jud-basedow syndrome (excessive iodine intake) Factitious Thyrotoxicosis (excessive thyroxin intake) Ectopic thyroid H secretion (teratoma) Thyroid carcinoma Malignancies with thyroid stimulators Pitutary adenoma stimulating TSH (Thyroid - stimulating

hormone)

THYROTOXICOSIS

IMPORTANT NOTE

1- Thyrotoxicosis may be confused with acute anxiety

2 -In thyrotoxicosis, hands are sweaty and warm

3- In acute anxiety, palms are cold and clammy

1-Anti-thyroid drugs Inhibit synthesis of thyroxin by

interference with trapping, oxidation and coupling of iodide.

Most commonly used drugs are carbimazole and propylthiouracil (PTU)

2- Radioactive iodine: I131 is commonest isotope used and the aim is to destroy the thyroid tissue. 3- Surgery : The aim is to remove the thyroid tissue by Subtotal thyroidectomy (Preserves about 4g (10%) of thyroid tissue). Patients must be euthyroid prior to operation

Detection of undiagnosed disease Symptoms Signs Referral Patient with diagnosed disease Determine original disease Past therapy Current medication Assessment of clinical status Referral if necessary

Prevent the occurrence of life threatening situations ( Myxedema coma or thyroid storm)

Prevent the exacerbation of complications associated with them as cardiovascular diseases

Avoidance of the following in untreated or poorly treated patients:

Surgical procedures Acute infection Epinephrine in local anesthetic solutions

and gingival retraction cords

Patient under good medical treatment: Supine position Patient on PTU should be given stress management

medications as diazepam, lorazepam

For local anesthesia, use mepivicaine only If patient is off the anti-thyroid drug, THEN you can use

lidocaine,prilocaine , bupivicaine (max= 2 carpules) Epinephrine concentration as low as possible (1:200.000) over (1:100.000) over (1:50.000) In block injections, aspiration before injection Implement normal procedures and management Avoid atropine since it may lead to increase in heart

rate and precipitate a thyroid storm

Patient under good medical treatment

Avoid acute infection

Treat all chronic infections

Patient on PTU causes agranulocytosis, thrombocytopenia and has an anti-vitamin k activity

Always check the complete blood picture (CBC), platelet count , prothrombin time and NR (normalized ratio)

Thyroid storm Life-threatening exacerbation of

thyrotoxicosis. Has a mortality of 50%. Precipitating factors

Thyroid surgery, Radioiodine ,Withdrawal of antithyroid drugs, Acute illness (e.g. stroke, infection, trauma)

Clinical featuresSevere thyrotoxicosis, fever,

delirium ,seizure or coma, tachycardia, congestive heart disease, profuse sweating, .

Treatment

ABC (BASIC LIFE SUPPORT)

Patency of airway (Head tilt-chin lift)

Assessment of breathing

Administration of O2 ( 100% - FLOW RATE 10L/ MIN)

Assessment of adequacy of circulation

If available , establish an IV LINE for 5% dextrose and water or

normal saline

Wet or ice packs

Medical assistance at once

High antithyroid drugs, beta- blockers, 200-300mg

hydrocortisone to prevent adrenal insufficiency

Sedation, hydration and electrolyte balance

Detection of undiagnosed disease Symptoms Signs Referral Patient with diagnosed disease Determine original diagnosis Past therapy Current medication Assessment of clinical status Referral if necessary

Avoidance of the following in untreated or poorly treated patients

Surgical procedures Acute infection CNS depressants (opioid analgesics, sedative

hypnotics as barbiturates and other anianxiety drugs

Administration of such drugs may become an overdose---- respiratory / or cardiovascular depression

Patient under good medical treatment:

Avoid acute infection Implement normal procedures and

management

An exacerbation of hypothyroid signs and symptoms

Usually in old people Seek medical aid Basic life support measures (BLPM) Oxygen – 100%- flow rate 10L/Min) I.V or i.m Hydrocortisone (100-300mg)

Myxedematous crisis:

ThyrotoxicosisOsteoporosis of alveolar bone

Dental caries and PDD

Teeth and jaw develop rapidly

Premature loss of deciduous teeth

Early eruption of permanent teeth

Lingual thyroid

Hypothyroidism

Infants with hypothyroidism

may demonstrate thick lips,

enlarged tongue, delayed

eruption of teeth,

malocclusion

In adults there is

macroglossia