3. Decrease secretion or function of thyroid gland or thyroxin. 1.PRIMARY HYPOTHYROIDISM : Due to diseases of thyroid gland. Without Goitre : eg; Idiopathic /Autoimmune Atrophic Hypothyroidism, Radioactive Iodine Therapy, Thyroidectomy, Congenital Agenesis, Transient(Infection, Post partum thyroiditis, Thyroid hormone withdrawal). With Goitre : eg; Hashimoto’s Thyroiditis, Drug Induced(INF, ATD, Amioderone, Lithium), Endemic Iodine Deficiency, Dyshormonogenesis/Inborn Errors, Infiltrative disorders ( Amyloidosis, Sarcoiudosis, Riedel’s thyroiditis. 2. SECONDARY HYPOTHYROIDISM: Due to pituitary lesions. 3. TERTIARY HYPOTHYROIDISM: Due to hypothalamic lesions.

4. CLINICAL FEATURES : COMMON: Weight gain, Cold intolerance, Fatigue, Somnolence, Dry skin & hair, Menorrhagia. LESS COMMON: Constipation, Hoarseness, Carpal tunnel syndrome, Alopecia, Aches & pains, Muscle stiffness, Deafness, Depression, Infertility, Malar flush, Periorbital edema/Myxedema, Loss of lateral eyebrows, Anemia, Carotenemia, Bradycardia, Hypertension, Delayed relaxation of tendon reflexes, Dermal myxedema. RARE: Psychosis ( Myxedema madness ), Galactorrhea, Impotence, Ileus, Ascites, Pericardial & Pleural Effusion, Cerebellar Ataxia, Myotonia.

5. INVESTIGATIONS: 1.T4 : Decreased. 2.TSH : Increased ( > 20 Mu/L ). 3. Thyroid peroidase antibodies, Antibodies to Thyroglobulin & TSH receptors : Increased. 4.Serum CK, AST, LDH : Increased. 5. Cholesterol : Increased. 6.Na : Decreased. 7.Anemia : NCNC / Macrocytic. 8.ECG : Sinus bradycardia, Low voltage complexes, ST- Segment & T wave changes.

6. MANAGEMENT: Thyroxin replacement therapy:  1 st 03 weeks = 50 micro grams/day.  Next 03 weeks = 100 micro grams/day.  maintenance = 100- 250 micrograms/day IN ISCHEMIC HEART DISEASE & ELDERLY PATIENTS:  Initial = 25-50 micro grams/day along with beta blockers and vasodilators. In non-responders to beta blockers and vasodilators PTCA or CABG may be required. HYPOTHYROID AND PREGNENCY:  Pregnant women require 50 micro grams more thyroxin than non- pregnant due to increase serum TBG.

7. MYXEDEMA COMA: Severe Hypothyroidism In Elderly Patients. H ypothermia. Hypoglycemia. Hyponatremia. Confusion or Coma TREATMENT IN MYXEDEMA COMA:  Inj: T3 20 micro grams I/V x 8 h for 48-72 h or Levo Thyroxin Na (400 micro grams I/V stat than 100 micro grams/day) followed by oral thyroxin 50 micro grams/day or through N/G tube.  Oxygen inhalation.  Hydrocortisone (100 mg I/V stat followed by 25-50 mg I/V 8 h).  5% D/W.  Broad spectrum antibiotics.  Gradual re-warming by blankets.