Congenital hypothyroidism in Indian preterm babies - screening, prevalence, and aetiology.

INTRODUCTION: Paucity of data on hypothyroidism in Indian preterms. Aim of the study: To describe the prevalence, aetiology, and experience with screening for primary hypothyroidism in preterm babies. MATERIAL AND METHODS: A prospective observational study conducted for 3 years in a tertiary care unit, where all babies born < 37 weeks screened by heel prick for Thyroid Stimulating Hormone (TSH) were included. All screen positive cases (TSH ≥ 6 µIU/ml) underwent venous testing immediately; venous TSH ≥ 20 or Free T4 < 0.9 ng/dl was considered as confirmed positive. All babies underwent venous testing at term. Etiological testing was performed where feasible. Confirmed cases were initiated on thyroxine therapy and followed up. RESULTS: 1167 preterm babies presented during the study period. 1147 (98%) underwent TSH screening and 17 (1.4%) were screen positive; 15 babies underwent confirmatory venous test. Of these 15 babies, 2 were confirmed and started on therapy. The remaining 13 babies underwent retest venous sample at term, and 8 of these were confirmed cases. Of the screen-negative babies, 94% underwent repeat venous testing at term/ prior to discharge. Five were confirmed to have congenital hypothyroidism. Thus, the prevalence of congenital hypothyroidism was 1 in 77 preterm babies. No correlation was observed between screening TSH and venous TSH (p > 0.05). Aetiological evaluation in 8 babies revealed secondary to maternal antibody in 4 cases (50%) and permanent thyroid defects in 4 cases (50%). CONCLUSIONS: We observed a high prevalence (1 in 77), need for repeat venous testing, irrespective of initial screening, and significant permanent congenital hypothyroidism (50%) in our series.

Impact of maternal thyroid disease on neonatal thyroid status.

OBJECTIVES: Prevalence of Maternal and congenital hypothyroidism is on the rise. To present the thyroid stimulating hormone screening results in babies born to hypothyroid mothers and assess the burden, aetiology of hypothyroidism in these babies. METHODS: All antenatal mothers attending our hospital during the study period were enrolled into the study. Group I includes 249 term babies born to hypothyroid mothers and group II comprises 2154 newborns born to mothers who are euthyroid. Heel prick thyroid stimulating hormone was done for all newborns on day 3 for both groups. Confirmatory venous testing was done for all for babies in group I and screen positives belonging to group II. Evaluation and therapy done as per standard guidelines. RESULTS: Thyroid stimulating hormone values in the two groups are presented. There was significant correlation between peak maternal thyroid stimulating hormone and neonatal day 3 heel prick in group I (r=0.7, P<0.05). The prevalence of positive screening test in groups I and II was 3.8 and 1.03% (p<0.05) whereas corresponding values for confirmed disease was 4.3 and 0.6%, respectively (p<0.05). Aetiological evaluation revealed both transient hypothyroidism (33.3%) and permanent hypothyroidism (66.6%). CONCLUSION: 4.3% of babies born to hypothyroid mothers develop congenital hypothyroidism; aetiology being both transient and permanent. A venous test by 3 weeks is helpful in these babies to improve case identification.