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Endocrinal System Thyroid and Parathyroid

INDIAN DENTAL ACADEMY Leader in continuing dental education

Thyroid • Endocrine gland situated in the neck. • Two lobes joined by an isthmus. • Secretes two hormones Thyroxine(T3) and Triiodothtroxine(T4)

Regulation of thyroid gland activity • Thyroid gland is an effector component of classic hypothalamic-anterior pitutaryperipheral gland axis. • Major stimulator- TSH or thyrotropin from anterior pitutary. • Direct stimulator for TSH is TRH or thyrotropin-releasing harmone from hypothalamus. • Negative feedback mechanism.

Actions of thyroid hormone • • • •

Whole body actions : Increase the whole body consumption of Oxygen and heat production. Increase the cardiac output. Accelerates the response to starvation. Metabolic disposal of other hormones and many drugs are increased.

Effects on growth and development • Stimulates linear growth, development and maturation of the bone. • Accelerates secretion of growth hormone. • Normal skeletal muscle function also requires thyroid. • Has critical effects on the development of CNS. • Contributes to the reproductive function of both genders.

Disorders of thyroid function • Hyperthyroidism : • More common in women in the age range of 20-40 years. • Three conditions account for most cases Grave’s disease Toxic multinodular goitre Solitary toxic nodule

• Clinical features : • Characteristic eye changes- Exoptholmous, limitation of ocular movement and optholmoplegia. • Increase in BMR • Heightened level of anxiety and restlessness • Intolerance to heat. • Pretibial myxoedema

• • • • • • • • •

Management : Antithyroid drugs – Carbimazole Beta blockers Radioactive iodine Total or subtotal thyroidectomy. Dental aspects : GA is risky – chances of dangerous dysrythmias Sedation may be necessary – N20 is safer Risk of giving adrenaline containing LA is more of theoretical risk. • Thyroid crisis !!!

Hypothyroidism • Commonest cause is chronic autoimmune hypothyroidism- two clinical forms Goitrous form (Hashimoto’s disease) & Atrophic form • Other causes – surgical removal, radiation, iodine deficiency and some drugs. • Common in women in the age group 60 yrs

• Clinical features : • Often unrecognized • Weight gain, lassitude, dry skin and loss of hair. • Bradycardia and heart failure. • Neurological and psychological changes like sleeplessness, irritability and mental dullness. • Hoarseness,hypothermia and cold intolerance. • Associated autoimmune disease like Sjogren’s syndrome.

• Dental aspects : • Main danger is of precipitating myxoedema coma by sedatives(diazepam), opioids, tranquillizers and general anaesthetics. • Local anaesthesia is safe and preferrable. • Stunted growth is most marked feature of cretinism.Also eruption and shedding of primary teeth are delayed. • Additional problems may be posed by associated hypopitutarism and Sjogren’s syndrome.

Parathyroids • Four pea-sized glands located on the back of thyroid gland. • Secrete parathyroid hormone(PTH). • Secretion is controlled by negative feed back mechanism. Stimulated by fall in the plasma ionized calcium.

• Actions of PTH : • Acts on kidneys, GIT and bone. • PTH and vit D both act to control plasma Ca levels. • Increases renal re absorption of calcium and impairs phosphate re absorption. • Enhances GI absorption of calcium. • Promotes osteoclastic bone resorption which is reflected in a rise in plasma level of calcium and alkaline phosphatase enzyme.

Hypoparathyroidism • Most common cause is thyroidectomy. • Muscle irritability and tetany is the classical feature with Facial twitching(Chvostek’s sign) Carpopedal spasms(Trousseau’s sign) Numbness and tingling of arms and legs • Other uncommon features like Psychiatric disorders Dental defects Constipation Etc.

• Diagnosis and management : • Blood biochemistry Low plasma calcium and often raised phosphate. • Therapy : Replacement therapy includes Vit D and calcium supplements. Vit D 500-3000 micrograms/day, Calcium 2-3 gms/day.

• Dental aspects : • LA is safe • Dental management may be complicated by tetany, Seizures, psychiatric problems and learning disabilities. • Congenital forms may feature enamel hypoplasia, shortened roots and sometimes delayed eruption.

Hyperparathyroidism • Three types – Primary hyperparathyroidism : usually caused by a parathyroid adenoma seen in post menopausal women. Secondary hyperparathyroidism : is a response to plasma low calcium levels secondary to chronic renal failure or prolonged dialysis. Tertiary hyperparathyroidism : follows prolonged secondary hyperparathyroidism that has become autonomous.

• Clinical features : • “Stones, bones and abdominal groans” • Hypercalcaemia leading to Renal disease – renal calcifications (stones) Skeletal disease – bone pain, pathological fractures and giant cell tumors. GI - Peptic ulcers and pancreatitis. Others – hypertension and sometimes dysrhythmias. • Hyperparathyroidism may sometimes be associated with tumors of other endocrine glands (MEN I, II and III).

• Diagnosis : • Confirmed by raised parathyroid hormone levels – raised serum calcium. Plasma phosphate levels may be low. • Enzyme alkaline phosphatase level will be normal unless there is significant bony involvement. • Management : • Surgical : Parathyroidectomy. • Medical : active Vit D hormone(1,25dihydroxycholecalciferol). Also hydration, increased salt intake and mild forced diuresis.

Dental aspects • LA is preferred over GA. • Dental treatment may be complicated by Renal disease – may impair drug excretion. Peptic ulceration – may limit the choice of analgesics. Bone fragility – pathological fractures. • Dental changes : • Loss of lamina dura and generalized bone rarefaction. • Giant - cell lesions of hyperparathyroidism (Browns tumor).

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