Thyroid and Parathyroid Drug Therapy

The thyroid and parathyroid glands produce hormones responsible for metabolism, growth, and development. The thyroid gland produces the thyroid hormones T3, or triiodothyronine, and T4, or thyroxine. Thyroid medications are primarily used to treat hypothyroidism which is a decrease in thyroid hormones; and hyperthyroidism, which is an increase in these thyroid hormones.
The parathyroid glands, on the other hand, produce parathyroid hormone, or PTH for short. So parathyroid disorders include hypoparathyroidism, which is a decrease in PTH, and hyperparathyroidism, which is an increase in PTH. Let’s start with the treatment for hypothyroidism, which often presents with weight gain, weakness, fatigue, and cold intolerance. Treatment involves thyroid hormone replacement therapy with levothyroxine, which is a synthetic form of T4.
In contrast, hyperthyroidism presents with weight loss, anxiety, an elevated heart rate and blood pressure, as well as bulging eyes, or exophthalmos. Hyperthyroidism is treated with methimazole or propylthiouracil, which suppress the synthesis of thyroid hormones. Now, hypoparathyroidism, will often present with signs and symptoms of hypocalcemia, like numbness in the hands, feet, and mouth, as well as cardiac arrythmias and tetany, or involuntary muscle cramps. It’s treated with calcitriol, or vitamin D3, which increases blood calcium levels.
In contrast, hyperparathyroidism presents with signs and symptoms of hypercalcemia, which can be remembered by ‘stones, bones, abdominal groans, and psychiatric overtones’ meaning kidney stones, osteoporosis, abdominal pain and constipation, and depression and fatigue. It can be treated with cinacalcet, which decreases blood calcium levels.
As far as side effects go, levothyroxine can cause headaches, insomnia, nausea, and weight loss, as well as hyperthyroidism. Importantly, it has a Black Box warning that it should not be used for weight loss. Side effects of methimazole and propylthiouracil include headaches, nausea, skin rash, as well as hypothyroidism. Hepatitis and jaundice can also occur. In fact, propylthiouracil has a Black Box warning for being highly hepatotoxic, potentially causing severe liver injury and acute liver failure. Now, the most common side effects of calcitriol are headache, drowsiness, and dry mouth, as well as nausea, vomiting, and constipation. Other important side effects include hypertension, cardiac arrhythmias, as well as hypercalcemia.