Posted on March 27, 2009
Hypothyroid patients required increased levothyroxine during pregnancy
Women with underlying hypothyroidism during pregnancy
required different levothyroxine dosages.
Researchers conducted a retrospective review of 38 women
with managed hypothyroidism during pregnancy and analyzed data on 45
pregnancies. The researchers collected thyroid function test data when
pregnancy was confirmed and then every four to eight weeks. The thyrotropin
goal was 0.4 mcU/mL to 4.1 mcU/mL.
All women required a cumulative increase in
levothyroxine dosage from baseline: first trimester, 13%; second trimester,
26%; and third trimester, 26% (P<.001 for all).
Patients with primary hypothyroidism were assigned an
average levothyroxine dose of 92.5 mcg per day. These patients required a small
cumulative increase of 11% in the first trimester (P=.125) and 16% in
both the second and third trimesters (P=.016 for both).
Patients with hypothyroidism resulting from treated
Graves’ disease or goiter were assigned an average levothyroxine dose of
140.4 mcg per day. The largest cumulative dosage increases were among patients
in this group: first trimester, 27%; second trimester, 51%; third trimester,
45% (P=.063 for all).
Patients with thyroid cancer were assigned an average
levothyroxine dose of 153.2 mcg. These patients required a 9% cumulative
increase in the first trimester (P=.03), 21% in the second trimester
(P<.001) and 26% in the third trimester (P<.001).
“Patients require vigilant monitoring of thyroid
function upon confirmation of conception and anticipatory adjustments to
levothyroxine dosing based on the etiology of their hypothyroidism,” the
researchers wrote.
Loh JA. Thyroid. 2009;doi:10.1089/thy.2008.0413.
