TSH neonatal como marcador del estado de nutrición de yodoinfluencia de la yoduria y la función tiroidea maternas sobre la TSH neonatal

Abstract

Introduction Neonatal thyroid stimulating hormone (nTSH) is a marker of iodine nutrition status in the population. The WHO considers a prevalence of less than 3% of nTSH levels greater than 5 mIU/L in samples obtained within 72 h from birth indicative of iodine sufficiency. The aim of this study was to determine the prevalence of nTSH levels greater than 5 mIU/L in an iodine-sufficient population and its association with maternal, neonatal and obstetric factors. Materials and methods A total of 243 pregnant women were recruited between May and June 2017 in our health area. A questionnaire of iodine intake was administered, in addition to determination of ioduria, thyroid function and autoimmunity in the first trimester of gestation. We analysed nTSH levels in samples collected between 48 and 72 h post birth and other obstetric and neonatal factors. Results The mean nTSH level (standard deviation) was 2.43 (1.68 mIU/L), with 7.8% of neonates having levels greater than 5 mIU/L. The highest nTSH levels corresponded to neonates of mothers with insufficient ioduria (p = .021) or TSH levels greater than 2.5 mIU/L, in both the case of negative (p = 0.049) and positive (p = 0.006) thyroid autoimmunity results. Maternal ioduria greater than 150 μg/L was a risk factor for nTSH levels greater than 5 mIU/L (3.70 [1.06–14.60]; p = 0.046), while a neonatal weight of 2500 g or greater was a protective factor (0.14 [0.02–1.00]; p = 0.038). Conclusions The prevalence of nTSH levels greater than 5 mIU/L in our health area was high based on the WHO recommendations. Maternal iodine deficiency was associated with a higher risk of nTSH levels less than 5 mIU/L. Given that nTSH is currently measured before 72 h post birth, we need new cut-off points to keep on using nTSH as a marker of iodine nutritional status.