Hyperthyroidism, particularly Graves’ disease, is more common in women than men, especially in women of childbearing age. Untreated hyperthyroidism in pregnancy can affect both the mother and the developing baby. The preferred antithyroid drug in non-pregnant women is Methimazole. During pregnancy, the current American Thyroid Association guidelines recommend propylthiouracil as the drug of choice for newly diagnosed Graves’ disease and to switch to propylthiouracil if already on therapy. The reason for this is that, while both of these medications have been associated with birth defects when used in the first trimester, the risk is lower and the defects appear to be less severe with propylthiouracil. Both antithyroid drugs also have similar side effects, including the rare, but potentially serious, side effect of agranulocytosis (low white blood cells) that can lead to potentially serious infections, and the more rare side effect of liver failure. The goal of this study was to determine the frequency of these two adverse side effects as compared to birth defects in the general population and in pregnant women in an effort to guide the treatment of hyperthyroidism in pregnancy.
THE FULL ARTICLE TITLE:
Andersen SL et al. Antithyroid drug side effects in the population and in pregnancy. J Clin Endocrinol Metab 2016; 101 (4): 1606-14. Epub January 27, 2016.
SUMMARY OF THE STUDY
Children born from January 1st, 1973 until December 31, 2008 and their parents were identified using the Danish Medical Birth Register. Exposure to antithyroid drugs was obtained from the Danish National Prescription Register, which contains information from January 1st, 1995. Information on the outcomes was obtained from the Danish National Hospital Register, which contains inpatient diagnoses since 1977 and inpatient and outpatient diagnoses since January 1995. All visits from January 1st 1995 until December 31, 2010 were included. Birth defects registered before the age of 2 years were included. To study the pregnant women, the population was restricted to women who gave birth to a live-born child between 1996-2008. The study population included 2,299,952 people, out of which 28,998 people were treated with antithyroid in the study period.