Drinking May Alter Thyroid Function
Janary 18, 2002
JTO News Summary

A new study found that drinking alcohol may alter thyroid function in pregnant women and their unborn children, Reuters reported Jan. 16.

The study by researchers at Texas A&M University was conducted on mother sheep and their unborn lambs. The researchers simulated human binge-drinking behavior in sheep that were in their third trimester of pregnancy. The sheep were given either doses of alcohol or saline solution for three days, followed by four days with no alcohol or saline. The researchers then measured levels of thyroid hormone in the animals' blood.

The researchers discovered that alcohol consumption reduced the levels of thyroid hormone in both the sheep and the fetus.

"The administration of alcohol to sheep during the equivalent of the third trimester of pregnancy resulted in altered thyroid function in both the mother and fetus," said lead researcher Dr. Timothy A. Cudd.

Since thyroid hormone is necessary for proper brain development in humans, the study may provide a link between thyroid function and alcohol-related birth defects.

The study is published in the January issue of the journal Alcoholism: Clinical and Experimental Research 2002;26:53-58

Fetal alcohol syndrome, thyroid level may be tied
Researchers seek ways to prevent brain damage
By Brad Evenson, National Post Online 1/19/2002

Researchers have discovered a mechanism they believe causes brain damage in babies born with fetal alcohol syndrome (FAS), a finding that could help doctors prevent the tragic disorder in the womb.

If the findings are confirmed, women could be monitored during pregnancy and treated with readily available synthetic hormones that could mitigate the effects of alcohol on the fetus.

The U.S. experiments also suggest pregnant women who drink alcohol in their third trimester may deprive their babies of a hormone critical for brain development. This may raise questions about the commonly held belief that it is safe to drink moderately after 27 weeks of pregnancy.

The study is published today in the journal Alcoholism: Clinical & Experimental Research.

Roughly three of every 1,000 babies in Canada suffer from FAS, a pattern of birth defects and learning and behavioural problems caused when mothers consume alcohol during pregnancy. Some telltale symptoms, such as cleft palate, can be corrected by surgery, but there is no treatment to reverse the brain damage FAS causes.

The syndrome is widespread among aboriginal Canadians, especially in remote areas, where it affects up to 3% of newborns.

Despite the efforts of doctors and even warning labels on liquor bottles, the rate of FAS has not fallen in the 29 years since it was first defined, so medical researchers have strived to find a way to block the damage by learning how alcohol harms the fetus.

One important clue is the similarity of birth defects in FAS babies and those born to mothers who suffer a shortage of thyroid hormone, which is important for fetal development.

In both conditions, babies suffer damage to the hippocampus and cerebellum.

"From a behavioural standpoint, children born to hypothyroid mothers score less well on intelligence, attention, language, reading ability and school performance measures," said Timothy Cudd, professor of physiology at Texas A&M University and lead author of the study.

"From an anatomical perspective, these deficiencies are similar to those in children with [FAS]."

To determine whether alcohol caused thyroid hormone levels to fall, the Texas researchers gave pregnant sheep doses of alcohol through catheters starting at 109 days of gestation. Since sheep give birth at 145 days, this was the equivalent of the third trimester of human pregnancy.

The sheep got doses of alcohol ranging from 0.75 to 1.75 grams per kilogram of body weight for three days to mimic a pattern of binge drinking. At the higher dose, that's the equivalent of about eight shots of whisky a day in a pregnant woman of average size, and 3.5 shots at the lowest dose.

Next, they collected blood samples from the mother and the fetal lamb. At higher doses, the alcohol "resulted in altered thyroid function in both the mother and the fetus," Dr. Cudd said.

Catherine Rivier, a professor of neuroendocrinology at The Salk Institute in La Jolla, Calif., says this study is important because it sheds light on how alcohol harms fetuses.

"Prior to this study, we knew that, in general, fetal brain development requires thyroid hormones to grow normally and build all the right connections," she said.

"We knew that children born to mothers who have low thyroid hormone levels are often retarded. These results show us that alcohol given to a pregnant mother lowers thyroid hormones in both the fetus and the mother."

Dr. Cudd says although ewes are a good model for women, since their thyroid systems are similar, further studies are required to understand this process in humans.
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