Hypothyroxinemia: a subclinical condition affecting neurodevelopment

Abstract

Hypothyroxinemia with low levels of circulating free thyroxine and normal levels of thyrotropin, which is usually caused by iodine deficiency, may affect pregnant women even in apparently iodine-sufficient areas, and it is debated whether it increases the risk of neurodevelopmental abnormalities in children born to them. Epidemiological observations indeed indicate that this is the case. Animal models show abnormal brain cortical cytoarchitecture in pups born to mildly hypothyroxinemic dams. In regions where the availability and use of iodized salt is inadequate (where <90% of households use iodized salt), the WHO and the International Council for Control of Iodine Deficiency Disorders (ICCIDD) recommend iodine supplementation so that the total iodine intake is 250 µg/day to prevent iodine deficiency during gestation and lactation.

Keywords::

• cerebral cortex
• iodine deficiency disorders
• iodine supplementation
• neurocognitive outcome
• pregnancy
• transient hypothyroxinemia of preterm children

Acknowledgements

The authors thank G Morreale de Escobar for critical reading of the manuscript.

Financial & competing interests disclosure

Work in the author’s laboratories is supported by Spanish MICINN Grants PN I+D+I SAF2009-10689, SAF2008-01168 and SAF2008-00429E, the Center for Biomedical Research on Rare Diseases (CIBERER), and the European Union Integrated Project CRESCENDO (LSHM-CT-­2005-018652). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.