Endocrine Abstracts

Recent guidelines indicate that pregnant women with subclinical hypothyroidism (SCH, TSH above the pregnancy-related reference range where available, or ≧2.5 mU/l) should be treated with thyroxine. We aimed to determine the frequency of overt hypothyroidism (OH; TSH>5 mU/l) and SCH (TSH >2.5 but <5 mU/l) in pregnancy, and to examine how many are diagnosed with thyroid problems after pregnancy. Four thousand three hundred women were recruited between 2007 and 2010. Plasma samples were obtained at gestational weeks 12–14. Delivery information was obtained from hospital databases. Thyroid stimulating hormone (TSH) and free thyroxine (fT4) levels were analysed in 2014 using clinically validated platforms (Roche). In women with TSH >2.5 mmol/l hospital records were used to identify more recent thyroid problems. Eighty-six women were known to have pre-existing thyroid disease and were not included in the analysis. Fifty-five women (1.3%) were identified as having OH. Of these one was diagnosed during pregnancy, 12 have been diagnosed since pregnancy, and one diagnosed with Grave’s disease. Another three women have had elevated TSH but have no formal diagnosis, five have had TFTs in the normal range, and 33 have had no TFTs checked. 396 women (9.4%) were identified as having SCH. Of these none were diagnosed during pregnancy, 14 have since been diagnosed with hypothyroidism, two have been diagnosed with Grave’s disease, four developed post-partum thyroiditis. 21 women have had elevated TSH but have no formal diagnosis. 179 have since had TFTs within the normal range. In this unselected obstetric cohort 9% of pregnant women have SCH, and according to recent guidelines these women should be treated with thyroxine. Of them, only 5% have subsequently been diagnosed with thyroid disorders, compared to 25% of women with OH. Screening of TFTs in all pregnant women, and associated treatment of SCH would have major implications for costing and design of obstetric services.