Biochemical and histochemical studies on the pituitary-testicular axis in obese (C57Bl/6J-ob/ob) mice

Male C57Bl/6J-ob/ob mice (4 months old) and their homozygous lean controls were compared with respect to pituitary LH secretion and functional parameters of purified Leydig cells in vitro. Compared with controls, obese mice showed reductions in the following parameters: Plasma testosterone levels (reduced by 57%), hCG-stimulated testosterone formation in vitro (by 31%), conversion of progesterone to androgens by Leydig cells (by 39%), and GnRH-stimulated LH secretion (by 26%). Lipid accumulation and a 37% decrease in naphthylesterase activity in the Leydig cells as well as hyperplasia of pituitary gonadotrophs were observed histochemically in obese mice. The changes in testicular endocrine function in obese mice are interpreted as consequences of pituitary dysfunction.