Chapter 32: Thyroid & Antithyroid Drugs

Chapter 32 details the fundamental anatomy and pharmacology related to treating disorders of the thyroid gland, which is responsible for regulating metabolism via the essential hormones thyroxine (T4) and triiodothyronine (T3), a process controlled by TSH. The chapter addresses hypothyroidism, characterized by a deficiency in these hormones, which can manifest as cretinism in youth or myxedema in adults. Hypothyroidism is primarily treated with synthetic hormone replacement drugs, such as levothyroxine (T4), which is favored for its chemical purity and predictable effects. These replacement medications function like endogenous thyroid hormones, increasing the metabolic rate, stimulating the cardiovascular system, and raising oxygen consumption. Conversely, hyperthyroidism, or thyrotoxicosis, resulting from excessive hormone secretion—often caused by Graves’ disease—is managed using antithyroid drugs like methimazole and propylthiouracil. These antithyroid agents work by inhibiting the necessary incorporation of iodine molecules into tyrosine, thereby impeding the formation of T3 and T4. The nursing process emphasizes careful patient assessment, especially monitoring for cardiac dysrhythmias or symptoms of toxicity (like heat intolerance and palpitations) when administering replacement drugs, as well as watching for serious adverse effects like bone marrow suppression or agranulocytosis caused by antithyroid agents. Patients require education on the necessity of lifelong therapy, the importance of taking thyroid replacement in the morning on an empty stomach for optimal absorption, and avoiding abrupt cessation of either drug class.