Chronic ethanol treatment reduces the responsiveness of the hypothalamic-pituitary-thyroid axis to central stimulation.
The hypothalamic-pituitary-thyroid (HPT) axis functions abnormally in man and animals chronically exposed to ethanol. The most consistent observation in humans is that the thyrotropin response to thyrotropin-releasing hormone (TRH) is blunted. We have tested the hypothesis that chronic ethanol treatment in rats leads to a diminished responsiveness of the hypothalamus to central stimulation. Animals were maintained on 1 of 3 diets for 4 weeks: (1) laboratory chow and water provided ad libitum (chow-fed), (2) Sustacal chocolate liquid diet with vitamin mixture containing 5% (w/v) ethanol provided ad libitum (ethanol), or (3) Sustacal chocolate liquid diet with vitamin mixture containing sucrose substituted isocalorically (35%) for ethanol and provided in amounts matched to a weight-paired, ethanol-treated animal (pair-fed). At the end of 4 weeks, the animals were evaluated for their response to a single injection of ethanol (3 g/kg, ip) and/or exposure to 5 degrees C. Chronic ethanol treatment produced an increase in TRH mRNA in neurons of the paraventricular nucleus and fully blocked the thyrotropic response to cold exposure. However, chronic ethanol-treated animals did not exhibit altered basal levels of triiodothyronine or thyrotropin, nor did they have an altered response to a single injection of ethanol. These data demonstrate that chronic alcohol exposure alters functioning of the hypothalamic-pituitary-thyroid axis at least in part by affecting TRH neurons of the paraventricular nucleus.
Zoeller
R T
RT
Department of Anatomy and Neurobiology, University of Missouri School of Medicine, Columbia, USA.
Fletcher
D L
DL
Simonyl
A
A
Rudeen
P K
PK
D000437:Alcoholism / Q000503:physiopathology*; D000818:Animals; D000431:Ethanol / Q000633:toxicity; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000503:physiopathology*; D008297:Male; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013961:Thyroid Gland / Q000187:drug effects / Q000503:physiopathology*; D013963:Thyroid Hormones / Q000097:blood*; D013973:Thyrotropin-Releasing Hormone / Q000502:physiology*
D013963:Thyroid Hormones; D000431:Ethanol; D013973:Thyrotropin-Releasing Hormone