The Impact of Gestational Thyroid Hormone Concentrations on ADHD Symptoms of the Child

Context: Maternal hypothyroidism during pregnancy is associated with adverse neuropsychological development in the offspring. Objective: The objective of the study was to evaluate the effect of maternal thyroid dysfunction during pregnancy on a child's attention-deficit/hyperactivity disorder (ADHD) symptoms. Design, Settings, and Participants: The prospective, population-based Northern Finland Birth Cohort 1986 (9362 pregnancies; 9479 infants) included analysis of maternal TSH, free T-4, and thyroid-peroxidase antibodies (TPO-Abs) from early pregnancy samples (5791 women). Teachers evaluated the children's ADHD symptoms at 8 years using the Rutter B2 scale (5131 mother-child pairs), in which a high score indicated probable psychiatric disorders and three questions focused directly on ADHD. Main outcome measures: The odds ratios (ORs) and 95% confidence intervals (95% CIs) of child having ADHD symptoms and/or a high Rutter B2 score after exposure to increases in maternal TSH levels (after logarithmic transformation), low free T-4 levels, and TPO-Ab positivity was tested with logistic regression, adjusting for maternal/family covariates. Data were stratified by the child's gender due to interaction. Results: Among girls the odds of inattention (OR 1.18,95% CI 1.02-1.37), high Rutter B2 total score (OR 1.23, 95% CI 1.03-1.48), and combined ADHD symptoms (OR 1.39, 95% CI 1.07-1.80) significantly increased with every natural log increase in maternal TSH concentrations. Such findings were not evident in boys. No associations were seen between ADHD symptoms and low maternal free T-4 levels or TPO-Ab positivity. Conclusions: Increases in maternal TSH in early pregnancy showed weak but significant association with girls' ADHD symptoms.