A large American study found that low levels in key, body-regulating chemical may affect brain development in babies born to mothers who have experienced low levels during the first three month of pregnancy.
These hormones, also known as thyroid hormones, are made in the neck’s thyroid gland and influence fetal growth. Investigators have suspected that disruptions in their production, or hypothyroidism, may contribute to attention deficit/hyperactivity disorder (ADHD), which is the most common neurodevelopmental disorder of children in the U.S.
The new study, led by a NYU Long Island School of Medicine researcher and involving children from hypothyroidism mothers, found that these children were 24 percent more likely than children whose mothers had the diagnosis. Their findings also showed that ADHD in boys born to hypothyroid mother were four times more likely than ADHD in girls. Hispanic children of hypothyroid mothers had the highest chance of any ethnic group.
Morgan Peltier (PhD), study lead author, said that “our findings make it clear that thyroid health likely has an even larger role in fetal development and behavioral disorders like ADHD” Peltier is an associate Professor in the Departments of Clinical Obstetrics, Gynecology, Reproductive Medicine at NYU Winthrop Hospital. This hospital is part of NYU Langone Health.
The study found that hypothyroidism by a woman in her second trimester of pregnancy had no effect on her children. Peltier believes that this is because the fetus is now producing its own thyroid hormones, making it less vulnerable to her mother’s deficiency.
The new investigation, published in the Oct. 21 issue of the American Journal of PerinatologyThe study followed 329,157 children, from birth to age 17, who were all born in Kaiser Permanente Southern California hospitals. According to the study’s researchers, it is the first large-scale American study to examine the possible link between hypothyroidism in a mother and ADHD in her children. The American study, unlike European research, included children from diverse backgrounds and was followed for almost two decades. Lead author Peltier said that this long study period allowed researchers to better capture ADHD cases in children as they aged and went through school.
The team also analyzed the medical records of the children and collected key information about their mothers. This included details such as their age during pregnancy and race. The same criteria were used to evaluate all children for ADHD. This, according to the authors, helped prevent inconsistencies in the way cases were identified.
The findings showed that ADHD was diagnosed in 16,696 children. Hispanic children with low thyroid hormone levels in their mothers during pregnancy were at 45 percent higher risk than white children with the same condition.
Peltier believes that the team’s findings are strong enough for pregnant women with low levels of thyroid hormone to be monitored closely. He says that children whose mothers were low in thyroid hormones during pregnancy may benefit from early surveillance for signs and symptoms of ADHD. These include hyperactivity, inattention, and difficulty focusing. Research has shown that ADHD can be managed quickly and children are more likely to succeed in school and in social skills learning.
Next, the team will investigate whether hypothyroidism can increase the risk for other neurodevelopmental disorders like epilepsy, cerebral paralysis, and difficulties speaking. They also plan to investigate other factors that could increase ADHD in children such as pregnancy exposure to environmental toxicants like flame retardants in upholstered furniture or electronic devices.
Kaiser Permanente Southern California, NYU Langone Health provided funding for the study.