American Thyroid Association

American Thyroid Association

September 22, 2016
1 min read

Pregnancy loss, preterm delivery reduced with levothyroxine therapy

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DENVER — Levothyroxine therapy reduced pregnancy loss, preterm delivery and offspring with low birth weight or low Apgar score for women with subclinical hypothyroidism negative for thyroid peroxidase antibodies, researchers reported at the Annual Meeting of the American Thyroid Association

However, they found a higher incidence of gestational diabetes and premature rupture in membranes in women prescribed levothyroxine.

“The findings of our study suggest that levothyroxine therapy in pregnant women with subclinical hypothyroidism and negative [thyroid peroxidase] antibody status could be beneficial, but also associated with possible risks,” Spyridoula Maraka, MD, of the Mayo Clinic, told Endocrine Today. “In the setting of uncertainty regarding the expected benefits of levothyroxine in this population and while waiting for more clinical evidence to be available, clinicians should engage in frank, shared decision making with their patients when considering treatment options.”

S. Maraka
Spyridoula Maraka

Maraka and colleagues evaluated medical records of pregnant women with subclinical hypothyroidism negative for thyroid peroxidase (TPO) antibody evaluated at the Mayo Clinic from 2011 to 2013 to determine the potential benefits of levothyroxine therapy.

Participants were divided into two groups: those prescribed levothyroxine (n = 22) and those who did not start levothyroxine (n = 34).

The levothyroxine group had a higher thyroid-stimulating hormone level (median, 4.9 mIU/L) compared with the control group (median, 3.5 mIU/L; P < .001). Compared with the control group, the levothyroxine group experienced less pregnancy loss (9.1% vs. 17.7%), fewer preterm deliveries (4.6% vs. 23.5%) and no offspring with low birth weight (0 vs. 14.3%) or low 5-minute Apgar score (0 vs. 7.1%). However, the control group experienced less gestational diabetes (2.9% vs. 9.1%) compared with the levothyroxine group and less premature rupture of membranes (8.8% vs. 18.2%).

There were similar rates of gestational hypertension and preeclampsia in the groups.

Maraka said larger studies are needed to determine the effects of levothyroxine on pregnancy and offspring outcomes.

“These should evaluate the expected benefits in patients with different degrees of severity of subclinical hypothyroidism and TPO-antibody status,” she said. – by Amber Cox


Maraka S, et al. Poster 46. Presented at: 86th Annual Meeting of the American Thyroid Association; Sept. 21-25, 2016; Denver.

Disclosure: Maraka reports no relevant financial disclosures.