Data on the health of the cohort children were acquired from routine child welfare clinic visits, national registers, questionnaires, and clinical examinations. Parents completed a questionnaire on health, development, school, and social situations of the children at 7 to 8 years of age (90% response rate). The children’s main teachers completed a questionnaire on impairments in learning reading, writing, or mathematics (92% response rate). At age 16, the adolescents were asked to self-evaluate their school performance in Finnish language and mathematics, using a data-collection tool previously shown to reflect school grades accurately (80% response rate). About 5070 individuals had teacher-estimated performance at 8 years and about 4360 had scholastic self-evaluations at 16 years.
Mothers with hypothyroidism (overt plus subclinical) were more obese, smoked less, and had significantly higher median TPO-antibody levels. Obesity was also significantly higher in mothers with hypothyroxinemia, and maternal obesity is associated with reduced offspring IQ. Mothers who had hyperthyroidism had a significantly smaller percentage of offspring who were male (36%, vs. 51% female).
No differences were found between the 8-year-old offspring of the mothers who were euthyroid and those who had hypothyroidism, hypothyroxinemia, or hyperthyroidism. Overall, 16-year-old offspring of the 358 mothers who had hypothyroidism showed no overall difference in scholastic performance as compared with the offspring of euthyroid mothers, but when the 318 cases of subclinical hypothyroidism were analyzed separately, the risk of having difficulty in mathematics was increased as compared with the 4747 adolescents from euthyroid mothers. The 16-year-old offspring of the 124 mothers with hyperthyroidism (overt plus subclinical) also had an increased risk of difficulty with mathematics.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
In this Northern Finnish cohort, 16-year-old offspring of mothers with first-trimester tests that indicated subclinical hypothyroidism were at increased risk of having difficulty in mathematics. The 16-year-old offspring of mothers with tests indicating hyperthyroidism (overt plus subclinical) were also found to be at increased risk of having difficulty in mathematics. These data suggest another reason to consider screening for thyroid disease in the mother early in pregnancy.
— Alan P. Farwell, MD, FACE
ATA THYROID BROCHURE LINKS