NEONATAL THYROTROPIN PROFILE AS AN INDEX FOR SEVERITY OF IODINE DEFICIENCY AND SURVEILLANCE OF IODINE PROPHYLACTIC PROGRAM

Neonatal serum thyrotropin (TSH) level has been proposed as an index f or the monitoring and surveillance of an iodine prophylactic program. We have determined an effective way to put this idea into practice. Du ring the first phase of our study, neonatal serum TSH levels were obta ined from umbilical cord blood of neonates born in Chiangmai and Nan p rovinces, where several districts were areas of severe iodine deficien cy, and were compared with those of neonates born in Bangkok, which wa s a control area. The median and (95% CI [confidence interval]) of ser um TSH level of neonates born in Chiangmai 5.8 (5.7-5.9) mu U/mL was s ignificantly higher than in Nan 5.1 (5.0-5.2) mu U/mL, and in Bangkok 3.7 (3.7-3.8) mu U/mL. Neonatal serum free thyroxine (FT4) concentrati on in Bangkok was higher than in Nan, while the reciprocal was true fo r neonatal TSH concentration in randomly selected samples (FT4 1.6 [1. 6-1.7] ng/dL vs. 1.5 [1.5-1.6] ng/dL and TSH 3.5 [3.3-3.9] mu U/mL vs. 5.5 [5.2-5.9] mu U/mL, respectively.) When odds ratio of the likeliho od of having neonatal TSH level higher than in Bangkok was calculated using 95th percentile value of neonatal TSH level in Bangkok as a cuto ff point, the odds ratio of TSH profile in all districts in Chiangmai and Nan were greater than unity. In the second phase of our study, dat a were collected from 32 district and 10 provincial hospitals. The opt imum number of samples in each hospital derived from the first phase o f our study was at least 178. Discrepancy between goiter rate and odds ratio of TSH profile was observed, but there was a significant correl ation between the two indices (r = 0.67, P < .001). Our study confirme d the practical utility of neonatal TSH profile as a biological index for assessment and monitoring and surveillance of an iodine prophylact ic program at a district hospital in a developing country.