Treatment of Thyroid Disorders - BMC Notes PDF

Treatment of Thyroid disorders  I- Treatment of Hypothyroidism: Levothyroxine (L-thyroxine): Thyroxine is the standard replacement therapy for hypothyroidism. Thyroxine has all the actions of endogenous thyroxine. Liothyronine (T3): It is the treatment of choice for myxoedema coma. Liothyronine has...

Treatment of Thyroid disorders  I- Treatment of Hypothyroidism: Levothyroxine (L-thyroxine): Thyroxine is the standard replacement therapy for hypothyroidism. Thyroxine has all the actions of endogenous thyroxine. Liothyronine (T3): It is the treatment of choice for myxoedema coma. Liothyronine has all the actions of endogenous triiodothyronine; and it is given intravenously Side effects: Nervousness, heat intolerance, sweating, palpitations, tachycardia, arrhythmias and unexplained weight loss. Indications: Myxedema and hypothyroidism. Drug-Drug Interactions: - Increased dosage is necessary: Estrogen, Bile acid-binding resins, Omeprazole, Phenytoin, Carbamazepine, Propranolol. - Reduced dosage is necessary: Glucocorticoids. II- Treatment of Hyperthyroidism: Principles of management of hyperthyroidism: Symptomatic treatment for thyrotoxicosis (e.g. beta blockers). Treatment of any reversible causes: offending medications (e.g. amiodarone and lithium), Definitive therapy for hyperthyroidism and thyrotoxicosis: [↓ synthesis and/or ↓ release of T3 & T4] including: 1. Anti-thyroid drugs thioamides (Methimazole, Propyl thiouracil) 2. Iodides 4. Partial or total removal of the thyroid. II- Treatment of Hyperthyroidism: II- Management of Hyperthyroidism (cont.): Definitive therapy for hyperthyroidism and thyrotoxicosis. 1. Antithyroid drugs: (Thionamides ) - Methimazole. - Propylthiouracil (PTU). Aim of treatment: ↓ synthesis and/or ↓ release of thyroid hormones, by: Mechanism of action: - Inhibition of synthesis of thyroid hormones T3 and T4 by Inhibiting peroxidase enzyme that catalyzes the iodination of tyrosine residues in the thyroglobulin. - PTU block the conversion of T4 to T3 within the thyroid & in the peripheral tissues Propylthiouracil Vs. Methimazole Propylthiouracil Methimazole Absorption Both are rapidly absorbed from GIT Protein binding 80-90% Most of the drug is free Excretion Kidneys as inactive metabolite Excretion slow,60-70% of within 24 hrs drug in 48 hrs Half life 1.5 hrs ( short half-life) 6 hrs ( long half-life) Given once daily Pregnancy Less crossing placenta Not recommended in (protein bound) pregnancy Recommended in pregnancy Breastfeeding Less secreted in breast milk Less secreted in breast milk Graves disease is the most common cause of hyperthyroidism N.B.1 If agranulocytosis occurred (severe leukopenia (most commonly neutropenia)) discontinue the anti-thyroid drug and give appropriate antibiotics. N.B.2 Hyperthyroidism in pregnant (1 st trimester give PTU- 2nd & 3ed trimester give methimazole ?????? II- Treatment of Hyperthyroidism: 2. Blockade of thyroid hormones release: Iodide. ( Lugol solution, potassium iodide) Mechanism of action: Inhibit thyroid hormone synthesis and release Block the peripheral conversion of T4 to T3. Indications: Prior to thyroid surgery to decrease vascularity & size of the gland. Following radioactive iodine therapy. Thyrotoxicosis The effect is not sustained (produce a temporary remission of symptoms). Side effects: Sore mouth and throat, swelling of the tongue, ulcerations of mucous membranes, and a metallic taste in the mouth. May produce iodism (swelling of salivary glands, mucous membrane ulceration, metallic taste, bleeding disorders and rarely anaphylaxis). Should not be used as a single therapy. Should not be used in pregnancy. II- Treatment of Hyperthyroidism: 3. Partial or total removal of the thyroid: either by radioactive iodine (131I) or surgically → thyroid tissue destruction - Indications of radioactive iodine (131I): e.g. failure to achieve euthyroidism with antithyroid drugs, high surgical risk. - Indications of surgery: e.g. - large goiter, obstructive symptoms e.g. dyspnea, dysphagia. - Sub-total thyriodectomy is the treatment of choice in very large gland or multinodular goiter II- Treatment of Hyperthyroidism: Symptomatic treatment β-blockers are effective in treatment of thyrotoxicosis to treat symptoms Propranolol is the most widely studied and used. Adjunctive therapy to relief the adrenergic symptoms of hyperthyroidism such as tremor, palpitation, heat intolerance and nervousness. E.g. Propranolol, Atenolol , Metoprolol. Propranolol is contraindicated in asthmatic patients Patients who cannot tolerate beta blockers may be treated with calcium channel blockers (diltiazem). Thyroid storm Extreme symptoms of hyperthyroidism. It is a medical emergency. Treatment is similar to hyperthyroidism, but the drugs are given in higher doses and more frequently. β-blockers are effective. A sudden acute exacerbation of all of the symptoms of thyrotoxicosis, presenting as a life- threatening syndrome. There is hyper metabolism, and excessive adrenergic activity, death may occur due to heart failure and shock. Thyroid storm Management Combination therapy: Hydration Potassium iodide 10 drops orally daily Propylthiouracil 250 mg orally every six hours or 400 mg every six hours rectally. Hydrocortisone 50 mg IV every 6 hours to prevent shock. Beta-blockers Thyrotoxicosis during pregnancy Management Better to start therapy before pregnancy with radioactive iodine (131I) or subtotal thyroidectomy to avoid acute exacerbation during pregnancy During pregnancy radioiodine is contraindicated. Propylthiouracil is the drug of choice during pregnancy.