Frequency and characteristics of thyroid dysfunction in pregnant women – screening of 547 women in Bulgaria

The Recommendations of the European Thyroid Association’2014 have been widespread among the medical community for many years. In them as well as in the latest Recommendations of the American Thyroid Association’2017 the first recommendation is related to the development of population-based reference limits based on data from the local population. The aim is to study the current functional thyroid status in pregnant Bulgarian women and to carefully assess in the light of modern understandings the specific diagnostic and therapeutic approach for our population. Material and Methods: The study was conducted as a cross-sectional multicenter population-based study, which included 547 pregnant women, mean age 30 ± 5 years. Fasting morning venous blood (TSH, FT4, TPOAb - determined by ECLIA method) and fresh morning urine sample (to determine urine iodine concentration) was taken, ultrasound examination of the thyroid gland was performed. Results: Based on the accepted cut-off for TSH according to the Recommendations of ETA’2014, the studied pregnant women were divided into six groups: Subclinical and Clinical hypothyroidism; Subclinical and Clinical hyperthyroidism; Euthyroid; Low T4 syndrome. Almost 2/3 of pregnant women have TSH < 2.5 mIU / L. Undiagnosed hypothyroidism is present in 121 pregnant women (22%), which is a bad feature of our health system. The data were analyzed in two TSH cut-offs (ETA’2014 and ATA’2017) and it was found that the increase in TSH cut-off for the first trimester did not change the absolute number of undiagnosed and untreated pregnant women with Clinical hypothyroidism, increasing 2.5 times its relative share, from 25.6% reaching 63.3% of all undiagnosed cases of hypothyroidism. Conclusion: Increasing the cut-off of TSH would unrealistically calm and neglect the follow-up of the pregnant women which is very dangerous. Efforts should focus on early screening for verbally identified risk factors. Of course, it is necessary to develop a national standard for TSH, which would serve more accurately to assess the thyroid status of pregnant women in the Bulgarian population.