Hyperthyroidism Basics for the Physician Assistant Exam
Hyperthyroidism is a condition the Physician Assistant Exam (PANCE) will cover Hyperthyroidism refers to an overactive thyroid gland. Hyperthyroidism has many causes, but the most common is Graves’ disease. Like Hashimoto’s thyroiditis, Graves’ disease is an autoimmune condition that usually affects young women. In Graves’ disease, the body forms antibodies that have a high affinity for the TSH receptor, the place on the thyroid that TSH would normally bind to.
Other causes of hyperthyroidism are easy to remember because they begin with the letter t. The two toxic causes are toxic adenomas and toxic multinodular goiter (TMG). These are common etiologies of hyperthyroidism, not as prevalent as Graves’ disease but in second place in the developed world.
Toxic adenomas are benign nodules that actively take up radioactive iodine on thyroid testing — the adenoma is the only area that’s active for the iodine uptake. With toxic multinodular goiter, you may see multiple areas of active iodine uptake. Thyroid nodules may not be present.
Signs and symptoms of hyperthyroidism
The classic triad of Graves’ disease includes goiter, pretibial myxedema, and exopthalmos. Exophthalmos is significant swelling of the eye tissues that can cause the eyeball to protrude. (Think of Bart Simpson with his big eyeballs.) In many cases of Graves’ disease, though, there’s milder ophthalmic involvement.
Other signs and symptoms can include high blood pressure with a widened pulse pressure, tachycardia, intolerance to heat, fever, diaphoresis, hyperdefecation, palpitations, tremor, increased reflexes, and moist skin (as opposed to the dry skin seen in hypothyroidism). Other behavioral abnormalities can include psychotic behavior and delirium.
If hyperthyroidism remains undiagnosed and unchecked, long-term sequelae include the development of atrial fibrillation, high calcium levels, and osteoporosis.
Older people can have a condition called apathetic hyperthyroidism. They have none of the symptoms mentioned earlier, but they can present with atrial fibrillation. Apathetic here does not mean that they don’t care about their atrial fibrillation.
Labs showing hyperthyroidism include a high free T4 and a low TSH level. The T3 level is often elevated.
How to treat hyperthyroidism
The treatment of hyperthyroidism is multifaceted. It involves treating not only the thyroid gland but also the peripheral manifestations of thyroid disease. One important medication class is the beta blocker, the most common being propranolol. It inhibits the peripheral conversion of T4 to T3, and because it’s lipophilic, can cross the blood-brain barrier. It’s good for helping not only high blood pressure and tachycardia but also tremor and other symptoms.
Thyroid-specific medications such as propylthiouracil (PTU) and methimazole (Tapazole) are used as well. Significant side effects of methimazole include hepatitis, drug-induced lupus-like syndrome, and negative effects on the bone marrow. These include thrombocytopenia, anemia, and agranulocytosis. Propylthiouracil, like methimazole, carries a risk of bone marrow suppression and liver problems. It increases the risk of developing significant autoimmune problems such as vasculitis and glomerulonephritis.
Two other options for hyperthyroidism are radioactive iodine-131 ablation and surgery. Radioactive iodine is the more customary therapy because it’s a permanent therapy. One side effect is the development of hypothyroidism over time; thyroid replacement therapy is often needed.
Radioactive iodine-131 (I131) ablation shouldn’t be used in pregnancy, nor should methimazole (Tapazole), which can cause fetal harm. Because methimazole has been found in breast milk, nursing mothers shouldn’t use methimazole, either. Opt for propylthiouracil if you’re taking care of a pregnant woman.
Surgery is less common because of its increased risk. Because the vagus nerve (recurrent laryngeal nerve branch) runs along this area, hoarseness related to injury to this nerve can be a complication of surgery.
Thyroid storm is a potentially fatal condition if not recognized. The affected person can present with high fevers, very high blood pressure, tachycardia, and psychotic and/or profound diaphoresis. The treatments include using beta blockers for managing the peripheral symptoms and either propylthiouracil or methimazole to decrease the synthesis of thyroid hormone. Intravenous steroids can also be administered. Close hemodynamic support and monitoring is essential.