SERUM LEVELS OF THYROID HORMONES IN PREGNANCY IN ILORIN: COMPARING UNIVERSAL WITH RISK SCREENING
Thyroid disorders are prevalent in women of child bearing age and commonly present during pregnancy and in the puerperium.
Unidentified thyroid dysfunction in pregnancy has adverse effects on foetal and maternal wellbeing, including miscarriage, preterm delivery, preeclampsia, abruptio placenta and post- partum hemorrhage. Thyroid disorders in pregnancy may be missed possibly because affected women could be asymptomatic. It is therefore important to consider the benefits or otherwise of universal screening for thyroid disease in pregnancy.
To determine serum levels of thyroid hormones, in pregnant women in Ilorin and proportion of asymptomatic thyroid disease in pregnancy.
The study was a comparative cross sectional study. Subjects were pregnant women between 14 and 25 weeks gestational age. Duration of gestation was calculated based on the first day of the last menstrual period for women who were sure of dates and from the first or early second trimester ultrasound for those who were unsure of dates. This population was further divided into two groups; those who were not at high risk of thyroid disorder and those who were at risk of thyroid disorder. High risk pregnant women were selected based on the Endocrine Society Clinical practice guidelines.7
Serum levels of thyroid hormones were determined in the whole study population using a highly sensitive and specific chemiluminescence immunoassay technique on Elecsys 2010 immunology analyzer (Roche diagnostic manhemm, Germany). Serum levels of thyroid hormones were compared in the high risk (targeted screening) and low risk (universal
screening) groups. Reference intervals for thyroid hormones for pregnant women at U.I.T.H were locally generated, prevalence of thyroid disorders was also determined.
The prevalence of thyroid disease in the high risk group pregnant women was 20.7% compared to 17.9% in the low risk group. The mean serum levels of TSH in the low risk group in this study was 2.59+ 1.42mIU/L which was higher than mean levels of 1.84+ 0.96mIU/L obtained in the high risk group. The difference was statistically significant (p value <0.001). Generated second trimester reference intervals for TSH, fT3 and fT4 in this study were 0.61- 4.80mIU/L, 0.20-1.60 pg/ml and 0.26-0.93 ng/dl respectively.
This study demonstrated that targeted screening (case finding) approach to screening for thyroid disease in pregnancy would miss about 87.9% of cases of hypothyroidism and 25% of cases of hyperthyroidism in low risk women.
Universal screening of pregnant women for thyroid disease in pregnancy is recommended.