BACKGROUND AND PURPOSE:

• Peltier et al. (Am J Perinatol., 2020) examined whether hypothyroidism prior to, or during, pregnancy increases the risk of attention-deficit hyperactivity disorder (ADHD) in offspring

METHODS:

• Retrospective cohort study (January 1, 2000 to December 31, 2016)
• Population
  • Singleton births
• Exposure
  • Maternal hypothyroidism: TSH >4.0 μIU/mL or fT4 ≤0.80 ng/dL
• Study design
  • Data were abstracted from linked maternal–child medical records
  • Incidence rate differences (IRDs), adjusted hazard ratios (aHRs), and their 95% confidence intervals (CIs) were used to determine associations
  • Stratification based on timing of first diagnosis, gestational age at birth (term vs. preterm), sex, and race-ethnicity
  • Covariates: Child sex | Race-ethnicity | Maternal age | Education | Median family household income | Parity, and Timing of prenatal care | Smoking habits during pregnancy | Gestational age at delivery

RESULTS:

• 329,157 births
• Hypothyroidism diagnosed prior to, or during, pregnancy increases the risk of ADHD
  • Prior: IRD 1.30; aHR 1.27 (95% CI, 1.15 to 1.41)
  • During: IRD 0.59; 1.17 (95% CI, 1.00 to 1.38)
• Association strongest when hypothyroidism was diagnosed during the first trimester
  • IRD 0.97; aHR 1.28 (95% CI, 1.04 to 1.58)
• Preterm: Significantly increased risk of ADHD if mothers diagnosed prior to, but not during pregnancy
  • IRD 3.06; aHR 1.43 (95% CI ,1.09 to 1.88)
• Association stronger for boys than for girls
  • Boys: IRD 1.84; aHR 1.26 (95% CI, 1.14 to 1.40)
  • Girls: IRD 0.48; aHR 1.19 (95% CI, 1.01 to 1.40)
• Risk was also stronger for Hispanic children compares to other races or ethnicities
  • IRD 1.60; aHR = 1.45 (95% CI, 1.25 to 1.68)
• Treatment effects
  • Maternal treatment with ≥50 μg/d thyroid supplementation was associated with increased risk for ADHD
  • aHR: 1.26 (95% CI, 1.14, 1.39)

CONCLUSION:

• Children born to mothers diagnosed with hypothyroidism preconception or first trimester were at an increased risk for developing ADHD
• Unclear if increased risk for ADHD in offspring treated with higher doses of thyroid supplementation is due to medication or more severe disease

Learn More – Primary Sources:

Maternal Hypothyroidism Increases the Risk of Attention-Deficit Hyperactivity Disorder in the Offspring

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