Neonatal thyrotropin - indicatior of monitoring of iodine deficiency severity. What’s level is considered a «cutoff point»?

Abstract

BACKGROUND: The issues of monitoring the effectiveness of iodine deficiency prevention programs are an important component in the process of iodine elimination. Neonatal thyrotropin (TSH) has been used as a criterion for the severity of iodine deficiency since 1994, however, the question of the “cut-off point” of the neonatal TSH level has been widely discussed in the recent literature.AIM: Evaluate the criterion for neonatal hyperthyroidism above 5 mIU/l from the perspective of monitoring iodine deficiency and establish a «cut-off point» on the model of healthy pregnant women with adequate iodine status.MATERIALS AND METHODS: A prospective study was conducted in a population of pregnant women in the city of Tyumen, with the formation of observation groups according to the level of iodine excretion in the urine — the main group (with adequate iodine status throughout the entire gestation period) and the comparison group (women with iodine levels less than 150 μg/l). The results of neonatal screening for congenital hypothyroidism in children of women participating in the study were evaluated. The frequency of neonatal TSH above 5mIU/l was assessed in the observation groups. ROC-analysis was performed and a «cut-off point» of the level of neonatal TSH was established as an indicator of iodine deficiency.RESULTS: The median urinary iodine concentration in the population of pregnant women in Tyumen was 159.05 μg/l, the incidence of goiter was 0.38%, the incidence of neonatal hyperthyroidism above 5 mIU/l was 2.88%, which characterizes adequate iodine intake in the pregnant population women. The frequency of neonatal TSH above 5 mIU/l in newborns from women from the main group was 1.47%, and in the comparison group — 9.3% (p = 0.076). ROC analysis revealed a threshold value of neonatal TSH of 2.77 mIU/l at the cut-off point, which corresponded to the highest value of the Youden index. Urinary iodine concentrations greater than 150 μg/l were predicted for nTSH values below this value.CONCLUSION: Analysis of databases of neonatal screening for congenital hypothyroidism makes it possible to effectively, quickly and at minimal cost annually assess the iodine status in the population. The established «cut-off point» of neonatal TSH in the model of healthy pregnant women with adequate iodine intake in our work is 2.77 mIU/l, the absence of statistically significant differences in the incidence of neonatal hyperthyroidism above 5 mIU/l from women with different iodine status during pregnancy indicate the need to revise the existing threshold of 5 mIU/l and may be an incentive to conduct large-scale studies in regions with different iodine supply.

Prevalence of high neonatal thyroid stimulating hormone levels as an indicator of iodine deficiency in the province of La Pampa: An epidemiological analysis

“…11 Although the WHO establishes a cut-off point of nTSH levels at 5 mIU/L to differentiate adequate and deficient iodine levels in a population, 1 a study that assessed pregnant women with adequate iodine levels and TSH levels in their newborn infants reported that the cut-off point for nTSH should be 2.77 mIU/L, lower than what has been proposed by the WHO. 25 Regardless of the cut-off point used, the prevalence of nTSH levels ≥ 5 mIU/L in our study was 9.6%, which suggests the presence of mild ID in the population of La Pampa. Although this study did not cover other indicators of ID, the percentage of nTSH ≥ 5 mIU/L mentioned above emphasizes the need for continuous monitoring of iodine nutritional status in the population, as even the presence of mild ID may result in significant damage to the neurodevelopment and other aspects of child health.…”

Prevalencia de hipertirotropinemia neonatal como indicador de deficiencia de yodo en la provincia de La Pampa: un análisis epidemiológico

“…11 Pese a que la OMS establece un punto de corte de TSHn de 5 mUI/l para diferenciar estados de suficiencia o DI en una población, 1 un estudio que evaluó a embarazadas yodosuficientes y las TSH de sus RN plantea que el punto de corte de TSHn debería ser de 2,77 mUI/l, un valor menor al propuesto por la OMS. 25 Independientemente del punto de corte considerado, la prevalencia de TSHn ≥5 mUI/l del 9,6 % encontrada en este estudio sugiere la presencia de una DI leve en la población de La Pampa. Aunque este estudio no abarca otros indicadores de DI, el mencionado porcentaje de TSHn ≥5 mUI/l enfatiza la necesidad de un monitoreo continuo del estado nutricional de yodo en la población, ya que incluso la presencia de una DI leve puede producir daños significativos en el neurodesarrollo y otros aspectos de la salud infantil.…”