Handling hyperthyroidism
By Jennifer Kearney-Strouse
In a Thursday talk at Internal Medicine Meeting 2021: Virtual Experience, Douglas Paauw, MD, MACP, offered listeners pearls on detecting and managing hyperthyroidism.
Some symptoms of the condition, such as weight loss, heat intolerance, and anxiety, are well known, whereas others are not, explained Dr. Paauw, who is a professor of medicine at the University of Washington in Seattle. "A lot of times people don't understand that the people that are hyperthyroid don't have diarrhea, they hyperdefecate. They have four to six formed stools a day," he said.
Muscle weakness, especially proximal muscle weakness, can also occur in patients who have had hyperthyroidism for a longer period, he noted, and amenorrhea is another possible symptom. "And remember, these people can get all sorts of arrhythmias," Dr. Paauw said, including tachycardia and atrial fibrillation.
Causes of hyperthyroidism include Graves' disease, toxic multinodular goiter, toxic adenoma, thyroiditis, ectopic/exogenous hormones, and medications, he said. Of these, Dr. Paauw noted, "Graves' disease is probably the most important. The other most important, in my opinion, is thyroiditis. This is super common, and with thyroiditis we're going to do a watch-and-wait approach, whereas the other causes, we tend to do more of a quick workup on them."
Palpable goiter is present on physical exam in 95% of patients who have hyperthyroidism due to Graves' disease, Dr. Paauw stressed. Other signs include onycholysis, hair thinning, and pretibial myxedema.
Abnormal lab values in hyperthyroidism include hypercalcemia, increased alkaline phosphatase, low total and HDL cholesterol, and impaired glucose tolerance, among others. "There are some interesting, really interesting presentations, including high-output heart failure, osteoporosis, new atrial fibrillation, and the rare thyrotoxic periodic paralysis," Dr. Paauw noted.
Sometimes, the history and exam will suggest a clear diagnosis, for example, if the patient has Graves' ophthalmopathy or has been taking thyroid hormone, Dr. Paauw said. "If you don't have a certain diagnosis, check thyroid antibodies, especially the thyroid stimulatory immunoglobulin, which is very good for diagnosing Graves' disease," he said.
If these tests don't provide an answer, radioactive iodine uptake might provide some clues, Dr. Paauw noted. Low uptake usually indicates thyroiditis or thyroid hormone ingestion, whereas high uptake points to Graves' disease, hyperfunctional adenoma, or toxic multinodular goiter, he explained.
To provide an example of how to manage subclinical hyperthyroidism, Dr. Paauw discussed the case of an 84-year-old woman with lower-extremity edema who has a low thyroid-stimulating hormone (TSH) level, at 0.15 mIU/L, but normal free T4 and T3 levels. "This is a person with subclinical hyperthyroidism, and we would just repeat the TSH in three to six months," he said. He noted that subclinical hyperthyroidism leads to overt hyperthyroidism in 6% of patients over the first year and rarely progresses after that time frame.
Dr. Paauw would consider treatment of subclinical hyperthyroidism in asymptomatic patients with a TSH level below 0.1 mIU/L. Treatment should be expedited in patients who have TSH level below 0.1 mIU/L and age greater than 65 years, heart disease, or osteoporosis. For patients with TSH levels of 0.1 to 0.4 mIU/L, observation with repeated testing is reasonable, he said.
"The bottom line I want you to remember is if the TSH is less than 0.1, we move on to a workup and treatment," he said. "If the TSH is between 0.1 and 0.4, we follow it, because that group rarely progresses." ■