Is an upper limit of 2.5 mUI/l for TSH appropriate for the first trimester of pregnancy among young TPO - women?

OBJECTIVES: The general purpose of this study is to assess the distribution among the various hormonal indices in young pregnant women with negative thyroid peroxidase antibodies and iodine sufficiency and classify them accordingly while comparing them to literature proposed reference values for the first trimester.

METHODS: A sectional study was carried out, including 127 pregnant women enrolled at the prenatal outpatient clinic at the Nova Iguaçu General Hospital, in the period comprised between 2000 and June 2007. They were submitted to TSH, free T(4), total T(4), TBG, and thyroid peroxidase antibody determinations.

RESULTS: A median equal to 38.7 microg/ml was observed for TBG; TSH values varied between 0.02 and 5.84 mcUI/ml, with a median of 1.25 mcUI/ml. For total T(4) and free T(4), median values were, respectively 10.3 microg/dl and 1.20 ng/dl. Thirteen patients out of 115 displayed a TSH serum level above 2.5 mUI/ml.

CONCLUSIONS: Patients with subclinical hypothyroidism classified by this new cutoff (serum TSH concentration between 2.5 mUI/l and the upper limit of the reference range), chiefly ATPO-negative young women display no need for treatment as there is no evidence that this condition is associated with maternal and fetal complications.