Study results from J.A. Loh et al provide new insights into hypothyroidism.

According to recent research published in the journal Thyroid, "In the United States, many women with hypothyroidism are on thyroid hormone replacement during pregnancy. The optimal management strategy for thyroid hormone dosing in hypothyroid women during pregnancy is controversial."

"We hypothesized that dosage requirements during pregnancy might differ depending upon the nature of the underlying hypothyroidism. We conducted a retrospective review of 45 pregnancies from 38 women whose hypothyroidism was managed during pregnancy. Thyroid function tests were obtained when pregnancy was confirmed, then every 4-8 weeks. The thyrotropin (TSH) goal was 0.4-4.1 mu U/mL (SI unit conversion: multiply TSH by 1.0 for mIU/L). On average, the entire group required a cumulative increase from baseline in levothyroxine (LT4) dosage of 13% in the first trimester, 26% in the second trimester, and 26% in the third trimester (p

The researchers concluded: "Patients require vigilant monitoring of thyroid function upon confirmation of conception and anticipatory adjustments to LT4 dosing based on the etiology of their hypothyroidism."

Loh and colleagues published their study in Thyroid (The Magnitude of Increased Levothyroxine Requirements in Hypothyroid Pregnant Women Depends upon the Etiology of the Hypothyroidism. Thyroid, 2009;19(3):269-275).

For additional information, contact K.D. Burman, Washington Hospital Center, Division Endocrinol, 110 Irving St. NW, Washington, DC 20010, USA.

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