Ethanol inhibition of pituitary-thyroid axis: an effect secondary to nutritional deficiency.
Ethanol as either 20% or 36% of total calories in a Lieber diet was administered to male rats. At these concentrations, ethanol consumption relative to body weight did not differ. Pair-fed controls were restricted to the amount of calories consumed by rats given ethanol. Under these conditions, a direct effect of ethanol on the hypothalamic-hypophyseal-thyroid axis could not be demonstrated. There were no differences between pair-fed control and ethanol treated rats in serum or pituitary TSH, TSH response to TRH, or T4 and T3 levels. On the other hand, in rats given ethanol as 36% of total calories ("36%" ethanol-treated), and in their pair-fed controls, a marked decrease in serum T4 levels occurred (25% and 30%), relative to the corresponding "20%" groups. The decreased T4 in the "36%" groups was associated with a pronounced fall in caloric intake, decreased serum TSH, and declines in adenohypophyseal and body weights -- all of which were of similar magnitude in experimental and control rats. Thus, inanition was probably the primary cause of reduced thyroid function in the "36%" groups. An interesting aspect of this change was the finding of no difference in serum T3 levels between pair-fed control and ethanol treated rats in the 36% and 20% groups despite the reduced T4 and caloric intake in 36% animals; the lack of decrease in T3 concentration in 36% animals may reflect augmented peripheral conversion of T4 to T3 or reduced T3 clearance.
D000818:Animals; D004435:Eating / Q000187:drug effects; D000431:Ethanol / Q000494:pharmacology*; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects*; D008297:Male; D009748:Nutrition Disorders / Q000503:physiopathology*; D010902:Pituitary Gland / Q000378:metabolism; D051381:Rats / Q000254:growth & development; D011919:Rats, Inbred Strains; D013961:Thyroid Gland / Q000187:drug effects*; D013963:Thyroid Hormones / Q000097:blood; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D013963:Thyroid Hormones; D000431:Ethanol; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin