Thyroid Medications span three categories with opposing risks that nurses must distinguish. Levothyroxine (T4 replacement): dosed precisely — too little leaves hypothyroidism undertreated; too much causes iatrogenic hyperthyroidism (palpitations, bone loss, atrial fibrillation risk in elderly). Administration: every morning on an empty stomach, 30–60 minutes before food. Calcium supplements, iron supplements, antacids, and PPI therapy reduce absorption — space by 4 hours. Methimazole and PTU (antithyroid drugs): inhibit thyroid hormone synthesis. Critical safety: agranulocytosis (sore throat + fever = stop drug, CBC stat, notify provider immediately — the nurse does not wait for the next scheduled appointment). Methimazole is preferred except first-trimester pregnancy (PTU used T1 because methimazole carries teratogenic risk; PTU carries hepatotoxicity risk in later trimesters → switch to methimazole after T1). Radioiodine (131-I) therapy: permanent thyroid ablation. Teaching: private bathroom, limit close contact with pregnant women/children for 1 week; expect post-treatment hypothyroidism requiring levothyroxine.