Maternal Thyroglobulin and Thyroid Function during Pregnancy and Offspring Neurodevelopment

Background: Low maternal urinary iodine concentration (UIC) during pregnancy has been associated with lower child IQ and differences in brain morphology. However, UIC is highly variable as it is a reflection of 24-h urinary intake rather than long-term iodine status. Thyroglobulin (Tg) might be a more sensitive biomarker of the long-term maternal iodine status.

Aim: To study whether maternal Tg is associated with maternal and newborn thyroid hormone concentrations, offspring IQ and brain morphology and if these associations differ by UIC.

Methods: We selected participants from two population-based prospective cohorts: Generation R (the Netherlands) and Instituto de Nanosciencia y Materiales de Aragon (INMA; Spain) with available measurements of maternal Tg and thyroid function at 13 weeks of gestation (N=4,438 women) or at birth (N=2,082 mother-child pairs), early childhood IQ (N=2,984; age 4.5 and 6 years) or late childhood IQ (N=2,569; age 9 and 13 years), and offspring brain morphology at 10 years (N=1,197). The associations of Tg with TSH and FT4 concentrations, IQ and brain MRI outcomes were studied with multivariable linear regression.

Results: Higher maternal Tg was associated with lower TSH (p<0.001), higher FT4 (p<0.001) and lower IQ in early childhood (p=0.02). Tg was not associated with cord blood TSH or FT4, late childhood IQ or brain morphology. We found no clear evidence of effect modification by UIC.

Conclusions: Tg is associated with thyroid function during pregnancy and some markers of offspring neurodevelopment. However, further research should determine the added value of Tg in addition to UIC for defining iodine status.