Dear Dr. Roach: About 35 years ago, a renowned Beverly Hills internist prescribed Armour Thyroid for me. At the time, I was burned out in a highly stressful job and would get bronchitis, usually twice a year. Although my thyroid was in the low-normal range, he felt it would boost my metabolism and improve my resistance to colds. It did. I am now retired and have not seen this doctor for more than a decade. I recognize that I can鈥檛 just quit taking a thyroid supplement, but is there a danger in continuing to take Armour Thyroid? Would I be better served by a synthetic version?
F.L.
The use of thyroid replacement for people who have symptoms of low thyroid but whose lab tests are normal or equivocal is common, but generally discouraged by experts. There are many reasons, apart from low thyroid hormone levels, to have symptoms such as fatigue or to get occasional infections. Chronic stress by itself certainly can predispose one to infection. Sometimes, people get better with this treatment, but whether they have truly low thyroid levels or whether it is a placebo effect might be impossible to know.
The body鈥檚 regulatory system of thyroid function consists of the pituitary gland, the hypothalamus of the brain and the thyroid gland itself. If someone with a normal thyroid starts taking a fairly low dose, then the body simply makes less thyroid hormone, provided the mechanism for sensing and adjusting the dose is intact. I suspect that your body is in this state of equilibrium now. If, however, you have been taking a higher dose than your body needs, then there is some danger, both to the bones and to your heart. Even if your body shuts off your own thyroid entirely, you might still be getting too much. Again, blood tests can help sort that out.
Armour Thyroid is made from pig thyroid, and has both thyroxine (also called T4, which is synthesized to make the most commonly taken thyroid replacement hormone) and triiodothyronine (also called T3, the active form of the hormone). Your current doctor could test your thyroid hormone levels to see whether you are in balance now, at least by blood tests. If so, your doctor could try to very slowly reduce the dose, keeping a careful eye on any symptoms you might have and on your blood tests. 听
The T3 in Armour Thyroid starts working very quickly. This can be dangerous in people with heart disease.
On the other hand, there are a very few people who cannot properly convert T4 to the active T3, so it is effective in some people who do not respond to synthetic T4. Being a natural product, it has more potential for variation, which is why many endocrinologists refuse to use it. The manufacturer reports testing both the raw material and the actual tablets to ensure the correct amount. Most endocrinologists prefer using thyroxine, and adding in synthetic T3 in a case of suspected inability to convert T4 to T3.
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 [email protected].
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