The association of lactating mothers’ urinary and breast milk iodine levels with iodine nutrition status and thyroid hormone levels of newborns

OBJECTIVE: To explore the iodine status of lactating mother-newborn pairs, and whether neonatal serum thyroid-stimulating hormone (TSH) can be used for estimation of iodine status of the population. MATERIALS AND METHODS: A total of 334 mothers and their healthy neonates were included. Urine, serum, and breast milk samples were obtained at 4th and 6th days of delivery. Urinary iodine concentration (UIC) was measured in urine samples of mothers and their neonates, as well as breast milk iodine concentration (BMIC) and serum thyroid hormone levels of neonates, were measured from the samples taken between the 4th and 6th days after birth. RESULTS: Median age of the mothers was 27 years (23–30). The median UIC of mothers and their newborns were 125 μg/L and 142 μg/L, respectively. The median BMIC was 138,0 μg/L. There was a significant positive correlation between the BMIC and UIC of neonates (r=0.276, p<0.001). The prevalence of neonatal serum TSH >10 mIU/L, which is suggestive of mild iodine deficiency (i.e. 3.0–19.9%), was 19.0%. However, there were no participants with iodine deficiency in lactating mothers and neonates according to UIC. CONCLUSION: By previous reports, Aydın is iodine sufficient. Although 19% of the neonates had serum TSH levels >10 mU/L, which is suggestive of a mild iodine deficiency, iodine deficiency was observed in none of the neonates and their mothers. Therefore, it will be appropriate to investigate the role of neonatal TSH levels in a larger sample to assess the iodine status of the population.