The incidence of congenital anomaly may be reduced by substituting potassium iodide for methimazole to control Graves’ disease during the first trimester of pregnancy, according to recent study findings published in Thyroid.
“This is the first study to evaluate whether switching from [methimazole] to [potassium iodide] in the first trimester of pregnancy decreases the incidence of major congenital anomalies in comparison with continuing treatment with [methimazole] alone,” the researchers wrote.
Ai Yoshihara, MD, PhD, of Ito Hospital in Tokyo, and colleagues evaluated 283 women with Graves’ disease who switched from methimazole treatment to potassium iodide in their first trimester between 2000 and March 31, 2013, and 1,333 women who received methimazole alone to determine the effect of potassium iodide treatment on congenital anomalies.
Compared with the methimazole group (4.14%), the incidence of major congenital anomalies was lower in the potassium iodide group (1.53%; P < .05). More newborns in the methimazole group had findings consistent with methimazole embryopathy (1.6%) compared with those in the potassium iodide group (0.8%).
Thyroid dysfunction or a goiter was not detected in any neonates exposed to potassium iodide. All newborns exposed to antithyroid drugs during the third trimester had detectable severe hypothyroidism (free thyroxine, < 0.9 ng/dL).
“In summary, switching from [methimazole] to [potassium iodide] in [Graves’ disease] patients during the first trimester of pregnancy may reduce the risk of congenital anomalies, at least in iodine-sufficient regions,” the researchers wrote. – by Amber Cox
The researchers report no relevant financial disclosures.