MONDAY, June 1, 2020 (HealthDay News) — Current practice patterns relating to testing and management of thyroid-stimulating hormone (TSH) during pregnancy are associated with overdiagnosis and overtreatment of hypothyroidism, according to a study published online June 1 in CMAJ, the journal of the Canadian Medical Association.

Jennifer M. Yamamoto, M.D., from the University of Calgary in Alberta, Canada, and colleagues conducted a retrospective cohort study of pregnancies in Alberta to examine the frequency and distribution of TSH testing by gestational age as well as TSH values associated with treatment.

The researchers found that 59.2 percent of the 188,490 pregnancies had at least one TSH measurement. Gestational week 5 to 6 was the most common time for testing. Thyroid hormone therapy was initiated at a median of 7 gestational weeks. Among women with first TSH measurements of 4.01 to 9.99 mIU/L who were not immediately treated, in 67.9 percent of pregnancies, the repeat TSH measurement was 4.00 mIU/L or less. For 44.6 percent of women who started therapy during their pregnancy, thyroid hormone therapy was continued postpartum.

“The practice of TSH testing early in the first trimester may be resulting in overdiagnosis and unnecessary thyroid hormone therapy during and after pregnancy,” the authors write. “Clinical practice guidelines are needed to give clinicians a stepwise approach, based on the best existing evidence, for deciding whether and when TSH testing should occur.”

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