Normal values of thyroid-stimulating hormone and free thyroxin in pregnant women

Abstract

Objective: To prepare a chart for normal values of thyroid-stimulatinghormone (TSH) and free thyroxin (free T4) and to verify the correlationbetween them, in pregnant women. Methods: A prospective crosssectionalstudy was performed on 850 pregnant women of thePrenatal Outpatient Clinic of the Hospital do Servidor Público Estadual– Francisco Morato de Oliveira (HSPE – FMO), from August 2003 toAugust 2005. Serum TSH and free T4 levels were determined usingmicroparticle enzyme immunoassay (MEIA). Maternal age ranged from18 to 47 years, mean of 32.5 ± 6.9 years. Mean gestational age was19.1 ± 8.5 weeks. With linear regression analysis, the 50th and 97.5thpercentiles for TSH and the 2.5th, 50th and 97.5th percentiles for free T4,at weeks 6 to 42 were calculated. The possible correlation betweenthese two indicators was analyzed. Results: Mean TSH and free T4values were 2.14 ± 1.51 μIU/ml and 0.98 ± 0.30 ng/dl, respectively.The correlation between free T4 and TSH levels was positive andstatistically significant according to the Pearson’s correlation coefficient(r = 0.069, p = 0.044). Conclusion: Identifying the normal TSH andfree T4 limits during pregnancy is the first step to safely determine thereal need for thyroid dysfunction treatment.

Keywords

• Thyroid-stimulating hormone
• Thyroxine
• Pregnancy
• Normal values