DEAR DR. ROACH: I am 81 now and had a thyroidectomy in 2017. My whole thyroid gland was removed. I also had a little bit of cancer. I have started to get hot flashes again. I had originally been on thyroid medicine before and after the surgery. Then I was put on levothyroxine and decided to try NP Thyroid. I was doing better on NP Thyroid, then started getting the hot flashes again. At this point, for several reasons, I would rather be on NP Thyroid for the time being.
I was wondering if there is anything I can take for the hot flashes? Years ago, in my 50s, I took estrogen that helped, but this is a different time. I have spoken with other people who are also having hot flashes again. — Anon.
ANSWER: Hot flashes are common — about 75% of women in North America will experience them around the time of menopause. It’s not uncommon for hot flashes to go away then return, but I haven’t personally seen them recur after 30 or so years. I’d be concerned that there may be another cause for the hot flashes, which brings me to your thyroid.
Elevated levels of thyroid hormone can cause sensations very similar to hot flashes. One reason I, along with most endocrinologists, recommend against products like NP Thyroid is because most of those products come from pigs. There are two thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Humans have a different ratio of T3 and T4 than pigs do, and T4 gets converted to the active form, T3. T3 is quickly broken down, so if it’s used, it needs to be dosed twice daily.
So, if a person takes NP Thyroid, their thyroid levels are too high during part of the day and too low during another. This isn’t good for anyone; the “high times” not only cause hot flashes, but also predispose people to atrial fibrillation. But it’s particularly a problem in a person with a history of thyroid cancer, where we want the thyroid-stimulating hormone (TSH, the hormone in the pituitary gland that regulates the activity of the thyroid gland) to be on the lower side.
If the thyroid blood levels get low in the afternoon/evening when the T3 in NP Thyroid is gone, that can theoretically increase the risk of cancer recurrence as the TSH rises in response. So, in my opinion, you should be on levothyroxine, not NP Thyroid. (I do have a handful of patients who take levothyroxine and also take T3 twice daily. There are a few people who cannot convert T4 to T3 efficiently.)
Estrogen is the most effective treatment for hot flashes, but it increases the risk of heart disease when used by women more than 10 years away from menopause. So, I don’t normally prescribe it to a woman in her 80s. However, there is a new medication, fezolinetant (Veozah), which is highly effective and reduced hot flashes by 93% in a trial. My only patient on it so far has reported 100% cessation of her hot flashes.
There are other rare causes of hot flashes, including tumors that secrete substances, such as carcinoid tumors, and tumors that secrete adrenalin-like hormones (pheochromocytomas).
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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.
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