Thyroid Deficiency In Pregnancy Affects Child IQ

Even a mild, symptom-free case of thyroid deficiency in a pregnant woman can affect her child's IQ scores years later, results of a study suggest. Children aged 7 to 9 who had mothers with untreated hypothyroidism in pregnancy had IQ scores about 7 points lower than youngsters of women without such a deficiency. The researchers note that for the first 12 weeks of pregnancy, before the unborn child's thyroid becomes active, the mother is the sole source of thyroid hormones. Studies suggest that these hormones play a role in brain development. Overall, compared with other children, the offspring of thyroid-deficient mothers had impaired school performance and lower scores on tests of attention, language, and visual-motor performance.

An editorial in NEJM notes that there are two potential causes of hypothyroidism in women: chronic autoimmune thyroiditis and iodine deficiency. Both causes likely play a role in thyroid deficiency in the US, where 15% of women of childbearing age had overtly inadequate intake of iodine between 1988 and 1994. With this in mind, the editorialist notes that efforts to increase dietary iodine intake in the US should be the first step in any program to help prevent the adverse effects of hypothyroidism during pregnancy. 

The New England Journal of Medicine 1999;341:549-555, 601-602.   

COMMENT: Another important recommendation for pregnant women. Please be sure and get your thyroid function tested. The most accurate way is described in my article section on my web site at One needs to measure FREE hormone levels in addition to a TSH level. If levels are low, one should consider going on Armour thyroid. It is likely that iodine supplementation will also work, but it would take too long to determine that during a critical phase of the child?s development. Armour thyroid has plenty of iodine in it and would address both iodine deficiency and thyroid hormone deficiency, so it would seem the route to pursue. Details of how to use Armour thyroid are also in the article. However, the editorial really served to get my thought processes in line and for non-pregnant adults it would certainly seem prudent to provide individuals with potassium iodine drops rather than Armour thyroid and rechecking levels in one month.

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