Previous studies have established that growth hormone (GH) has many important effects on the regulation of cholesterol and lipoprotein metabolism. However, human GH (hGH) can also bind to prolactin receptors, eliciting prolactin-receptor mediated effects. In this study, we evaluated if hGH can exert such responses in currently used animal models and whether prolactin affects lipoprotein and/or hepatic cholesterol metabolism. Normal and hypophysectomized (Hx) male rats were given either hGH or bovine GH, the latter unable to bind the prolactin receptor. The hormones were continuously infused using subcutaneous osmotic mini-pumps for 7 days; blood and livers were collected after sacrifice. Both hormones stimulated hepatic LDL receptor expression and bile acid synthesis to a similar extent, and normalized the altered plasma lipoprotein pattern in Hx rats. Prolactin, injected twice daily to Hx male rats, did not exert any effects on the plasma lipoprotein pattern nor on cholesterol metabolism. We conclude that previously established effects of hGH on cholesterol metabolism are not mediated by prolactin in male rats.