Endocrine Abstracts

As a component of thyroid hormones, iodine is essential for the development of the fetus, particularly for brain development. Though there has been no awareness of a problem of iodine deficiency in the UK for many years, it is becoming increasingly apparent that mild-to-moderate iodine-deficient is now present in certain population sub-groups. We assessed whether such a level of deficiency in UK pregnant women could be having an adverse effect on cognition in their offspring using samples and data from the Avon Longitudinal Study of Parents and Children (ALSPAC). Urinary iodine concentration (and creatinine to correct for urine dilution) was measured in samples from 1040 first-trimester pregnant women that had been stored at −20 °C. Based on the WHO criteria for deficiency/sufficiency in pregnancy, women’s results were dichotomised to <150 or ≥150 μg iodine/g creatinine. The relationships between maternal iodine status and child’s IQ at age 8 and reading ability at age 9 were analysed. Socio-economic, parental and child factors (n=21) were included as confounders. Overall the group was found to be mildly-to-moderately iodine deficient based on a median urinary iodine concentration of 91.1 μg/l (110 μg/g creatinine). Children of women with an iodine:creatinine ratio <150 μg/g were more likely to have scores in the lowest quartile for verbal IQ (OR 1.58, 95% CI 1.09–2.30), reading accuracy (OR 1.69, 95% CI 1.15–2.49), and reading comprehension (OR 1.54, 95% CI 1.06–2.23) than were children of mothers with an iodine:creatinine ratio ≥150 μg/g. When the <150 μg/g group was sub-divided, scores worsened on going from ≥150 to 50–150 μg/g to <50 μg/g. Our results show the importance of adequate iodine status during early gestation and highlight the risk that even a mild-to-moderate level of iodine deficiency can pose to the developing infant. This situation needs to be addressed urgently through public-health policy.