Maternal Thyroid Dysfunction During Pregnancy and Thyroid Function of Her Child in Adolescence

Normal maternal thyroid function is important for fetal development. No knowledge exists on how maternal thyroid function and thyroid antibodies during early pregnancy affect thyroid function of the offspring.The aim of this study was to investigate the relationship between maternal and adolescent thyroid function parameters.A total of 3673 mother-child pairs from the prospective, population-based Northern Finland Birth Cohort 1986 participated in the study. Maternal serum samples were drawn in early pregnancy (<20th gestational week), and children's samples were drawn at the age of 16 years and analyzed for TSH, free T4 (fT4), and thyroid peroxidase antibodies (TPO-Abs).TSH, fT4, and TPO-Ab concentrations were measured at the age of 16 years. Children of mothers with thyroid dysfunction (hypothyroidism, hyperthyroidism, or hypothyroxinemia) or TPO-Ab positivity were compared to those of euthyroid or TPO-Ab-negative mothers. The distributions are expressed as medians with 5th to 95th percentiles.Boys of hypothyroid mothers had higher TSH concentrations than those of euthyroid mothers: 2.0 (0.9-4.0) vs 1.7 (0.8-3.3) mU/L; P = .001. Children of hyperthyroid mothers had lower TSH concentrations than those of euthyroid mothers: 1.3 (0.6-4.2) vs 1.7 (0.8-3.3) mU/L, P = .013, for boys; and 1.3 (0.5-3.5) vs 1.6 (0.7-3.4) mU/L, P = .034, for girls. There were no differences in TSH or fT4 concentrations between children of hypothyroxinemic and euthyroid mothers. TPO-Ab-positive mothers more often had TPO-Ab-positive children (prevalence, 9.0 vs 3.7% among boys, and 22.7 vs 7.5% among girls).Maternal thyroid dysfunction and TPO-Ab positivity during pregnancy seem to modify thyroid function parameters of offspring even in adolescence. Whether this increases the thyroid disease risk of the children is still unknown.