Effect of perinatal factors on neonatal thyroid stimulating hormone

Abstract

Background: Congenital Hypothyroidism (CH) is a common cause of mental retardation. Its incidence varies in different parts of the world from 1:4000 to 1:2000. Objective: To study effect of perinatal factors on heel prick blood TSH levels and to find incidence of congenital hypothyroidism. Study Design: Prospective Observational birth cohort study. Method: Heel prick blood samples of total 3151babies, 1673 (53.1%) males and 1478 (46.9%) females was taken on special graded filter paper within 48 hours of life and screened by fluoroimmunometric assay. Babies with TSH value more than 9µU/ml were recalled at 5 to 7 days of life for repeat sample of T3, T4, TSH. Babies with low T4 less than 7 µgm/dl and TSH more than 20 µU/ml were labelled as congenital hypothyroidism. The effect of perinatal factors was analyzed statistically. Result: In our study, thyroid screening in two third of neonates was done at 12 to 24 hours of age. Median (IQR) TSH of 3151 neonates was 3(1.4-5.5) µU/ml. TSH level was significantly low in neonates with sampling at age of >24 hours. Recall rate in our study was 7.6% (238 cases) and 2 neonates were diagnosed as congenital hypothyroidism. Neonates with assisted deliveries showed a higher median (IQR) TSH level 5.3(3-9.1µU/ml) as compared to normal vaginal deliveries and lower segment caesarean section. This was statistically significant (p