Thyroid hormone levels in rats exposed to alcohol during development.

Maternal ingestion of alcohol appears to cause a pattern of congenital anomalies with a reduction of pre- and postnatal growth in the offspring. In order to study the possible implication of thyroid function in the effects of pre- and/or postnatal exposure to alcohol, we have studied serum thyroxine (T4) and triiodothyronine (T3) levels in rats from alcohol-fed mothers during the postnatal period (0-50 days). Blood alcohol levels of ethanol-treated pregnant rats were approximately equal to 20-25 mM and their serum T4 levels were decreased, compared with the pair-fed controls, at 15 and 21 days of gestation. No significant changes were observed in T3 levels. Prenatal alcohol exposure was associated with a decrease in both T4 and T3 levels in pups at birth. Although T4 levels continued reduced in the 40-50 days of the postnatal period, no clear effects were observed on T3 levels during this time. Moreover, the more marked alterations were obtained when the offspring were postnatally and pre + postnatally exposed to alcohol. Significant decreases were found in both T4 and T3 levels following postnatal exposure, except at the 20-25th day when a marked but transient increase in T4 levels was observed. These results indicate that alcohol exposure disturbs the hypothalamo-pituitary-thyroid axis, as measured by T3 and T4 hormone levels, mainly when the rats are exposed during the postnatal period.