### Date : 2024-06-24 08:53 ### Topic : Pharmacological treatment of hyperthyroidism and thyrotoxicosis #medicine #internalmedicine #endocrinology #thyroid ---- ### Pharmacological Treatment Options for Thyrotoxicosis and Hyperthyroidism Thyrotoxicosis refers to the clinical syndrome of excess thyroid hormone in the body, whereas hyperthyroidism specifically refers to disorders characterized by increased thyroid hormone production. Pharmacological treatment aims to reduce the levels of thyroid hormones, manage symptoms, and address the underlying cause. ### 1. Antithyroid Medications **a. Thionamides:** - **Methimazole (MMI):** - **Mechanism of Action:** Inhibits thyroid peroxidase, blocking the synthesis of thyroid hormones (T4 and T3). - **Indications:** First-line treatment for Graves' disease, toxic multinodular goiter, and toxic adenoma. - **Dosing:** Initial doses vary (usually 10-30 mg daily) based on severity; maintenance doses are lower (5-15 mg daily). - **Propylthiouracil (PTU):** - **Mechanism of Action:** Inhibits thyroid peroxidase and peripheral conversion of T4 to T3. - **Indications:** Alternative to methimazole, especially during the first trimester of pregnancy or thyroid storm. - **Dosing:** Initial doses are higher (usually 100-150 mg three times daily); maintenance doses are lower (50 mg two or three times daily). - **Side Effects:** Risk of hepatotoxicity, agranulocytosis, rash, and arthralgia. ### 2. Beta-Blockers **a. Non-Selective Beta-Blockers:** - **Propranolol:** - **Mechanism of Action:** Blocks beta-adrenergic receptors, reducing symptoms like palpitations, tremors, and anxiety; also inhibits peripheral conversion of T4 to T3 at high doses. - **Indications:** Symptomatic relief in hyperthyroidism and thyroid storm. - **Dosing:** Typical starting dose is 10-40 mg three to four times daily. **b. Cardioselective Beta-Blockers:** - **Atenolol and Metoprolol:** - **Mechanism of Action:** Similar to propranolol but more selective for beta-1 receptors. - **Indications:** Alternative for patients with contraindications to non-selective beta-blockers. - **Dosing:** Atenolol 25-50 mg once daily; Metoprolol 25-50 mg twice daily. ### 3. Iodine and Iodinated Compounds **a. Potassium Iodide:** - **Mechanism of Action:** Inhibits the release of thyroid hormones and reduces thyroid vascularity. - **Indications:** Preoperative preparation for thyroidectomy, treatment of thyroid storm, and short-term use in hyperthyroidism. - **Dosing:** Lugol's solution (5% iodine and 10% potassium iodide) 5-7 drops three times daily; SSKI (saturated solution of potassium iodide) 1-2 drops three times daily. ### 4. Radioactive Iodine Therapy **a. Radioiodine (I-131):** - **Mechanism of Action:** Radioactive iodine is taken up by the thyroid gland and destroys thyroid tissue through local radiation. - **Indications:** Definitive treatment for Graves' disease, toxic multinodular goiter, and toxic adenoma. - **Dosing:** Typically a single oral dose, calculated based on the size of the thyroid and iodine uptake. - **Considerations:** Not used in pregnant or breastfeeding women; risk of post-treatment hypothyroidism. ### 5. Corticosteroids **a. Prednisone:** - **Mechanism of Action:** Reduces inflammation and immune response; inhibits peripheral conversion of T4 to T3. - **Indications:** Thyroid storm, severe hyperthyroidism, and Graves' ophthalmopathy. - **Dosing:** Initial high doses (e.g., 40-60 mg daily) with gradual tapering based on response. ### Example Case Study **Patient Profile:** - **Name:** Jee Hoon Ju - **Age:** 38 - **Occupation:** Office Worker **Medical History:** - Diagnosed with Graves' disease, presenting with weight loss, palpitations, and tremors. **Treatment Plan:** 1. **Methimazole:** - Initial dose of 20 mg daily to inhibit thyroid hormone synthesis. 2. **Propranolol:** - 40 mg three times daily to control symptoms of palpitations and anxiety. 3. **Radioactive Iodine Therapy:** - Considered for definitive treatment after achieving euthyroid state with antithyroid medications. ### Conclusion Pharmacological treatment of thyrotoxicosis and hyperthyroidism includes antithyroid medications like methimazole and propylthiouracil, beta-blockers for symptomatic relief, iodine and iodinated compounds for short-term inhibition of hormone release, and radioactive iodine for definitive therapy. Corticosteroids are used in severe cases or for specific complications like thyroid storm and Graves' ophthalmopathy. The choice of treatment depends on the underlying cause, severity of symptoms, patient preference, and specific contraindications. Regular monitoring and follow-up are essential to ensure effective management and adjustment of therapy as needed.