Can Neonatal TSH Screening Reflect Trends in Population Iodine Intake?
- 1 August 2008
- journal article
- research article
- Published by Mary Ann Liebert Inc in Thyroid®
- Vol. 18 (8), 883-888
- https://doi.org/10.1089/thy.2008.0036
Abstract
Background: The distribution of neonatal blood thyroid-stimulating hormone (TSH) concentrations has been used as an index reflecting population dietary iodine intake, with higher concentrations being indicative of lower iodine intake. We examined this distribution in neonates born in Ireland, where the pregnant population has shown a recent decline in urinary iodine (UI) excretion. Our objectives were to determine if any alteration was observed in the percentage of values > 5.0 mIU/L and whether a trend in neonatal blood TSH was apparent. Methods: Samples drawn from the National Neonatal Screening Programme were assessed during the years 1995–2006 from winter (January n = 35,079) and summer (August n = 37,940) months, respectively, in view of the known seasonal variation in Irish dietary iodine intake. Results: Apart from the first years studied (1995–1996), the proportion of individual blood TSH values >5.0 mIU/L did not exceed 3%, a value believed to be indicative of iodine deficiency. A significant declining trend in the proportion of blood TSH >5.0 mIU/L was observed in subsequent years (p < 0.01). While excluding severe iodine deficiency, these analyses failed to detect the slight but highly significant (p < 0.001) tendency toward increasing blood TSH within the 0–5.0 mIU/L interval in the study population between 1999 and 2006, which was greater in summer than in winter months (p < 0.001). Conclusions: These data support a link between fetal thyroid function and a fall in maternal iodine intake. While the findings of the proportion of blood TSH values >5.0 mIU/L exclude severe maternal or fetal iodine deficiency, a trend toward increasing TSH may provide an early indication of impending iodine deficiency. The findings assume greater importance in the context of declining UI reported from many developed countries even where the proportion of blood TSH values >5.0 mIU/L is <3%, thus excluding severe maternal and fetal iodine deficiency.Keywords
This publication has 24 references indexed in Scilit:
- Iodine intake in pregnancy in Ireland — A cause for concern?Irish Journal of Medical Science, 2006
- Nutrient Effects upon Embryogenesis: Folate, Vitamin A and IodineNestle Nutrition workshop series. Paediatric programme, 2005
- Thyroid Hormone and Brain Development: Translating Molecular Mechanisms to Population RiskThyroid®, 2003
- Urinary iodine and thyroid status of New Zealand residentsEuropean Journal of Clinical Nutrition, 2001
- Iodine deficiency as a cause of brain damagePublished by Oxford University Press (OUP) ,2001
- Neonatal thyroid screening as a monitoring tool for the control of iodine deficiencyActa Paediatrica, 1999
- Screening for Congenital Hypothyroidism Used as an Indicator of the Degree of Iodine Deficiency and of its ControlThyroid®, 1998
- Iodine Nutrition in the United States. Trends and Public Health Implications: Iodine Excretion Data from National Health and Nutrition Examination Surveys I and III (1971-1974 and 1988-1994)Journal of Clinical Endocrinology & Metabolism, 1998
- What's Happening to Our Iodine?Journal of Clinical Endocrinology & Metabolism, 1998
- The Regulation of Thyroid Function in Pregnancy: Pathways of Endocrine Adaptation from Physiology to PathologyEndocrine Reviews, 1997