Gestational hypothyroidism carries risk of neonatal cognitive delays

A hypothyroidism diagnosis is problematic no matter what stage of life a person is in, but for pregnant women the risks can be especially great, since research indicates that children born to mothers with the thyroid disease can have intellectual delays.

This is one of the reasons that the American Thyroid Association recently released new guidelines concerning hypothyroidism among expectant mothers.

As reported in the journal Thyroid, an international panel of endocrinologists determined that even mothers with a subclinical variety of the disease should be treated with synthetic hormones. Likewise, the group supported the widespread use of blood testing to determine which mothers need more clinical attention paid to their glandular health.

Researchers emphasized that prenatal hypothyroidism poses risks to a baby's weight and their birth timing, potentially leading to premature delivery or even miscarriage. However, a baby born to a hypothyroid mother can also have subtler problems, ones that will only appear when the child begins to mature.

A pair of California scientists have noted that too little maternal thyroid hormone increases the risk that a child will have a lower-than-average intelligence quotient (IQ). Their findings appear in the medical text Fetal and Neonatal Brain Injury.

Drs. Kimberlee Sorem and Maurice Druzin - of the California Pacific Medical Center and the Stanford School of Medicine, respectively - estimated that a baby born to a mother with untreated overt hypothyroidism will have an IQ 7 percent lower than his or her peers.

Likewise, the pair stated that of all children born to untreated hypothyroid mothers, 19 percent will have an IQ under 85.

Several studies have noted that even subclinical thyroid hormone deficiencies may result in intellectual delays. For instance, a report in Thyroid announced that female laboratory rodents with subclinical hypothyroidism were more likely to have offspring with short- and long-term memory problems.

In it, scientists from China Medical University reported that these offspring tended to display lower levels of proteins related to neural health. Specifically, these mice had less brain-derived neurotrophic factor and Rap1 proteins, which encourage the growth of brain cells and stimulate neural firing, respectively.

The offspring of subclinically hypothyroid mothers also tended to take longer to navigate a water maze in the lab.

Researchers emphasize that mothers and doctors alike should watch for the symptoms of the thyroid disease before, during and shortly after pregnancy.

Approximately 5 percent of Americans have hypothyroidism, according to the National Institute of Diabetes and Digestive and Kidney Diseases.