Searchable abstracts of presentations at key conferences in endocrinology
Endocrine Abstracts (2007) 14 OC1.7

ECE2007 Oral Communications Thyroid clinical (7 abstracts)

Pregnant women on thyroxine substitution are often dysregulated in early pregnancy

Bengt Hallengren 1 , Mikael Lantz 1 , Bengt Andreasson 2 & Lars Grennert 3


1Department of Endocrinology, Malmö University Hospital, Malmö, Sweden; 2Department of Pediatrics, Malmö University Hospital, Malmö, Sweden; 3Department of Obstetrics and Gynecology, Malmö University Hospital, Malmö, Sweden.

Background: Thyroid hormones are important for normal fetal development. The aim of this prospective study was to explore whether thyroxine treated pregnant women with hypothyroidism are adequately thyroxine substituted during pregnancy.

Material and method: During the years 1997–2002 119 pregnancies in 101 females with thyroid diseases were followed at the Department of Endocrinology. The diagnoses were autoimmune thyroiditis (AIT) with or without hypothyroidism n=46, hypothyroidism (non AIT) n=9, status post Graves’ thyrotoxicosis (GD) n=33, active GD n=8, multinodular toxic goitre (MNTG) n=2, atoxic goitre with or without autonomous function n=20, operated thyroid cancer n=1 (+1 in the group status post GD).

Results: 64 patients were on thyroxine due to hypothyroidism at the first visit: 50% (32/64) had serum TSH values within the reference range (0.4–4.0 mIE/l) at first laboratory control. 20% (13/64) had TSH<0.40 mIE/l, 14% (9/64)≤0.1 mIE/l, 30% (19/64) had TSH>4.0 mIE/l, 14% (9/64)>10 mIE/l. 67% (44/66) had to increase the dose during pregnancy, 2/66 could stop thyroxine medication when finishing antithyroid drugs, 30% (20/66) did not have to change the dose.16 miscarriages, 1 late miscarriage, 1 intrauterine fetal death occurred. Of these 18/119 (15%) patients 78% (14/18) had TSH outside the reference range at first control. 44% (8/18) had TSH<0.40 mIE/l, 33% (6/18) had TSH>4.0 mIE/l.

Summary: In 50% of pregnant women on thyroxine substitution the serum TSH values were outside the reference range at first control. A majority had to increase the thyroxine substitution during pregnancy. In pregnant women with miscarriage a great majority had TSH values outside the reference range at first control. The study demonstrates that pregnant women with thyroxine substitution should be carefully checked and the thyroxine dose increased early in pregnancy to avoid hypothyroidism.

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