Tag Archives: PTU

Endocrinologists Take a Backward Step in the Treatment of Hyperthyroidism


When I became an endocrinologist in 1981 I was truly excited about the field. At that time it seemed that the science of endocrinology was expanding rapidly and new discoveries were on the horizon particularly in regards to the way hormones effect the brain, mood and the immune system. Was I ever wrong! It’s thirty years later and none of those expectations were realized. In fact, I find that the field of endocrinology has barely budged since then and in some areas has actually lost ground.

Bringing on this round of pessimism on my part, is a recent “development” in the area of treatment for hyperthyroidism (over active thyroid). Ever since I was in training there have been two medicines, propylthiouracil (PTU) and methimazole (Tapazole), which are the mainstays of medical treatment for hyperthyroidism. Both medicines have been available since the 1940’s and show excellent efficacy and tolerability (and they are cheap!). Almost all endocrinologists I have met use these two drugs interchangeably although in pregnancy propylthyiouracil is favored due to rare birth defects in fetuses exposed to methimazole.

The “development” which I find so discouraging is the recent action by the FDA to place a very strict (black box) warning on the use of PTU due to the possible occurrence of a rare form of liver injury attributed to the drug. After almost 70 years of exemplary use, this has given rise to extensive debate in the endocrinology literature about how to restrict PTU use.

While it is true that methimazole is equally as effective as PTU to treat hyperthyroidism, I have personally seen numerous cases of fairly severe allergic reactions to methimazole. Fortunately it has been easy to continue medical treatment by simply switching to PTU. If we can’t use PTU freely then the only other options are surgical removal of the thyroid or eradication of the thyroid using radioactive iodine, neither of which is free of potentially adverse outcomes.

I have never encountered severe liver injury with PTU nor has any of the colleagues I have polled. It has to be very, very rare. This is obvious because it has taken 70 years to get around to recognizing it formally. Can we really call it progress that we now have one less simple option for treating hyperthyroidism, a common and relatively benign disease? Let me take my cynicism to the next level. I won’t be surprised if a major pharmaceutical company soon announces the development of a new drug for treating hyperthyroidism. If I’m right the new drug will add nothing of real value that wasn’t previously available but is many times more expensive then the drug it replaces.

So goes endocrinology into the new century, the stogy old lady of medicine.

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