Dr. Roach: Beta blockers work with other hyperthyroidism meds

Keith Roach
To Your Health

Dear Dr. Roach: I am 80 years old. Two years ago, I was diagnosed with hyperthyroidism. I am taking methimazole 10 milligrams, two tabs daily. Whenever the endocrinologist reduces the tablets to once daily, my TSH remains low. I am also taking metoprolol. I read on my computer that beta blockers interfere with the absorption of methimazole. Should I take a different medication?

— M.W.

Dear M.W.: Hyperthyroidism is when the thyroid gland releases too much hormone into the blood. This may cause many symptoms, such as fast heart rate, tremor, anxiety, weight loss, excess bowel movements and shortness of breath. Methimazole blocks the synthesis of thyroid hormone, but often beta blockers such as metoprolol are also used to treat some symptoms, especially the fast heart rate, anxiety and tremor. Beta blockers work quickly and are usually prescribed as soon as hyperthyroidism is diagnosed.

Since they are so often used together, I was surprised to hear you read beta blockers block absorption of methimazole — nothing in medical literature supports that. It is true that once a person has gone from hyperthyroid to normal thyroid, the body can absorb metoprolol better, so the dose may need to be decreased.

TSH is “thyroid stimulating hormone,” the body’s signal to release thyroid hormone. In people with hyperthyroidism due to a problem with the gland -- Graves’ disease, an autoimmune thyroid disease — the TSH level is very low. More methimazole would be expected to raise the TSH, while decreasing the dose should make TSH lower.

Dear Dr. Roach: I am 84 years old and in good health. I recently read that most Americans don’t get enough potassium, which lowers blood pressure. Assuming I was one of the majority, I started taking a potassium Supplement. Wise Or Not?

— C.H.

Dear C.H.: A large 2012 study examining dietary habits concluded that the vast majority of Americans consume too much sodium and too little potassium. Increasing potassium uptake almost always lowers blood pressure. However, I still recommend lowering sodium and increasing potassium through diet rather than supplementation.

Less meat, less processed foods and of course less salt added to food all will decrease sodium. More fruits and vegetables will increase potassium. In addition, this dietary change has many other benefits, with the net effect of decreasing heart disease and cancer risk.

I don’t recommend a potassium supplement without a specific recommendation from your physician and unless your blood level has been tested and found to be in the normal or low range. It is possible to have high blood levels of potassium, despite a traditional American diet, perhaps due to kidney conditions associated with aging.

In general, there are very few (if any) supplements that benefit a healthy person with a good diet. Over-the-counter supplements can be useful alternatives to prescription medications for people with specific medical concerns, but should still be used with caution. Supplements are generally safer than prescription medicines, but they can cause harm if used incorrectly, in a person with unrecognized medical conditions or when taken at too high a dose. Finally, OTC supplements are not regulated the way prescription medicines are.

Readers may email questions to ToYourGoodHealth@med.cornell.edu.