Study Looks at Impact of Hypothyroidism, Hypothyroxinemia in Pregnancy

Subclinical hypothyroidism linked to higher rates of overt hypothyroidism or thyroid replacement therapy within five years of delivery

By Elana Gotkine HealthDay Reporter

WEDNESDAY, Aug. 21, 2024 (HealthDay News) — For women with subclinical hypothyroidism (SH) or hypothyroxinemia (HT) diagnosed during the first half of pregnancy, SH is associated with higher rates of overt hypothyroidism or thyroid replacement therapy within five years of delivery, according to a study published online July 31 in Thyroid.

Michael W. Varner, M.D., from the University of Utah Health Sciences Center in Salt Lake City, and colleagues conducted a secondary analysis of two multicenter treatment trials for SH or HT diagnosed between 8 and 20 weeks of gestation, focusing on individuals randomly assigned to the placebo groups.

The researchers found that one- and five-year follow-up data were available for 307 of 338 participants with SH and 229 of 261 with HT. Compared to those with HT, participants with SH more often had subsequent hypothyroidism at years 1 (13.4 versus 3.1 percent) and 5 (15.6 versus 2.6 percent). This progression was seen more often among those with thyrotropin values >10 mIU/mL. Among individuals with SH, a baseline thyroid peroxidase (TPO) level >50 IU/mL versus ≤ 50 IU/mL was associated with higher rates of hypothyroidism at years 1 and 5 (odds ratios, 5.3 and 5.4, respectively). Among individuals with HT, there were no differences seen in overt hypothyroidism at one year, while more participants with TPO levels >50 IU/mL developed hypothyroidism by year 5 (odds ratio, 13.4).

“Our data lend further evidence to the postpartum time period as a time when autoimmune diseases, in this case, hypothyroidism, are more likely to be present,” Varner said in a statement.