Endocrinology Drug Introduction Endocrine medications can be broken down into the following categories Diabetic Agents Hormone Agonists Hormone Antagonists Thioamides Drugs propylthiouracil (PTU) methimazole Mechanism inhibit thyroid hormone synthesis by blocking peroxidase-catalyzed reactions iodination of tyrosine residues of thyroglobulin coupling of DIT and MIT propylthiouracil ↓ peripheral conversion of T4 to T3 Clinical use HYPERthyroidism Toxicity skin rash agranulocytosis (rare) aplastic anemia Pregnancy use PTU methimazole crosses the placenta and enters breast milk Thyroid hormones Drugs levothyroxine synthetic T4 (thyroxine) triiodothyronine T3 Mechanism replaces endogenous thyroid hormones Clinical use HYPOthyroidism myxedema Toxicity thyrotoxicosis heat intolerance tachycardia dyspnea ↑ appetite tremors arrhythmias