When thyroid function is low, thyroid hormone needs to be replaced to ensure adequate metabolism and homeostasis in the body. When thyroid function is too high, the resultant systemic effects can be serious, and the thyroid will need to be removed or destroyed pharmacologically, and then the hormone normally produced by the gland will need to be replaced with thyroid hormone. Thyroid agents include thyroid hormones and antithyroid drugs, which are further classified as thioamides and iodine solutions. Following table includes a complete list of each type of thyroid agent.
When the correct dose of the replacement therapy is being used, few if any adverse effects are associated with these drugs. Skin reactions and loss of hair are sometimes seen, especially during the first few months of treatment in children. Symptoms of hyperthyroidism may occur as the drug dose is regulated. Some of the less predictable effects are associated with cardiac stimulation (arrhythmias, hypertension), central nervous system (CNS) effects (anxiety, sleeplessness, headache), and difficulty swallowing (taking the drug with a full glass of water may help).