Reference intervals in evaluation of maternal thyroid function during the first trimester of pregnancy

Background: Insufficient function of the thyroid gland can cause low concentrations of thyroid gland hormones which tire necessary for the proper development of the foetus brain, especially during the beginning of pregnancy. We determined the reference interval for TSH in the first trimester of pregnancy and the decision point for anti-TPO antibodies' positivity Methods: We tested 5520 women from the central part of the Czech Republic during the first trimester of pregnancy for serum TSH. anti-TPO and FT4 by chemiluminometric immunoanalysis on an AI)VIA Centaur system (Siemens). The reference interval for TSH during the first trimester of pregnancy was determined using the log transformation, and then summarized its the geometrical mean (95% CI); following which, a suitable decision point for anti-TPO positivity wits set. Results: The reference interval for TSH was determined to be 0.06-3.67 mU/l. The suppression of TSH was found in 2.93%, of the women; a raised concentration of TSH had been found in 4.48%, of the women. For anti-TPO, the cut-off was established at. 143 kU/l; 11.2%, of the pregnant women were found to be anti-TPO positive. Conclusion: Determination of the reference interval for TSH during early pregnancy is one of the basic requirements when implementing it general examination of the thyroid gland at the beginning of pregnancy The decision level for positivity of anti-TPO is more than double the manufacturer's reference interval.