Dr. Scott Rivkees, Chief of Pediatric Endocrinology at U. of Florida, and expert in anti-thyroid medication, discussed at a plenary lecture at American Thyroid Association\’s (ATA) meeting why the use of propylthiouracil (PTU) for the treatment of Graves disease is no longer recommended.
It has been well documented that children with Graves Disease have increased risk of hepatotoxicity (liver damage) when their hyperthyroidism is treated with PTU. Based on the work of Dr. Rickees and these data children with Graves disease are no longer being treated with PTU. They now receive treatment with Methimazole (MMI). MMI however carries the rare and potential risk agranulocytosis (bone marrow toxicity to precursor cells that make your white and red blood cells), when used at high doses. A risk that is much lower than that of liver damage.
For pregnant women with Graves we have special considerations. During the first trimester of pregnancy all of the baby’s organs are formed. There has been a concern about treating women who have Graves disease at this time because of the potential risk of developing malformations at this critical time. Up to now (2018) we had been treating women with PTU thinking that it might be safer in the first trimester. However, this assumption was not quite right. New review of the data shows that while both PTU and MMI pose risks, the risk for fetal malformations is lower with MMI. PTU therefore is not to be used on anyone with Graves unless there are no other option. The new recommendations for women are as follows:
- Avoid active Graves disease during pregnancy, to avoid using meds. Whenever possible women with Graves Disease should have “definitive” treatment of their graves before pregnancy Definitive treatment means that either they are in remission and are not using anti-thyroid medicines, or have had treatment with surgery or prior radioactive iodine.
- If one has to treat hyperthyroidism during first trimester use low dose MMI instead of PTU. The use of MMI in the first trimester decreases likelihood of any liver damage and of fetal malformations when low doses are used.
You might ask why do we have to treat mom’s hyperthyroid during pregnancy? We do this to prevent early pregnancy loss, and importantly to help the baby’s brain develop well and make healthy flexible neuronal connections.
I know you are curious as to what are the potential malformation that can develop with PTU? These are situs inversus (the left and right are reversed), problems with the heart, and urinary system.