The effect of alcohol on the foetus of two women may not be the same. One woman who drinks alcohol during pregnancy may deliver a child with physical, behavioural or learning problems, while another woman who also drinks alcohol may give birth to a `normal` child.
This is due to a gene variation passed on by the mother to her son. It contributes to a foetus` vulnerability to even moderate alcohol exposure by upsetting the balance of thyroid hormones in the brain.
The Northwestern University`s Feinburg School of Medicine study with rats is the first to identify a direct genetic mechanism of behavioural deficits caused by foetal alcohol exposure, the FASEB Journal reports.
"The findings open up the possibility of using dietary supplements that have the potential to reverse or fix the dosage of the thyroid hormones in the brain to correct the problems caused by the alcohol exposure," said Eva E. Redei, senior study author and professor of psychiatry at the Feinberg School of Medicine.
"In the not-too-distant future, we could identify a woman`s vulnerability to alcohol if she is pregnant and target this enzyme imbalance with drugs, a supplement or another method that will increase the production of this enzyme in the hippocampus, which is where it`s needed," Redei said.
Efforts to educate pregnant women about the risks of alcohol have not changed the percentage of children born with fetal alcohol spectrum disorder, Redei noted.
The gene involved, Dio3, makes the enzyme that controls how much active thyroid hormone is in the brain.
A delicate balance of the thyroid hormone is critically important in the development of the foetal brain and in the maintenance of adult brain function. Too much of it is as bad as too little.
When males inherit this variation of the Dio3 gene from their mother, they don`t make enough of this enzyme in their hippocampus to prevent an excess of thyroid hormones.
The resulting overdose of the hormones makes the hippocampus vulnerable to damage by even a moderate amount of alcohol.