The hypothalamo-pituitary-gonadal system was examined in male and female rats with experimental diabetes induced by streptozotocin (STZ). Injection of STZ caused a decrease of testosterone (T) concentration and of T nuclear receptors in the pituitary. The levels of luteinizing and follicle stimulating hormones (LH and FSH) in the blood of diabetic rats did not differ from those in intact animals. In vitro experiments showed that the development of diabetes did not change the basal secretion of LH by the pituitary in males. Maximal response to LH-RH was recorded in control males after 3-hour incubation, whereas the rate of LH secretion in experimental rats did not differ from basal values. Injection of STZ to cycling females disordered the estrous cycle and involved decreases of the basal and cyclic secretion of LH, FSH, and sex hormones. The concentrations of estradiol nuclear receptors in the preoptic anterohypothalamic region and pituitary decreased, whereas the number of T-binding sites decreased only in the pituitary. Sex hormone-stimulated gonadotropin wave in oophorect- omized females was decreased in diabetes, which was due to changed activity of the LH-RH producing system. The authors hypothesize that changes in the mechanism of regulation of the hypothalamo-pituitary-gonadal system in experimental diabetes are related to pituitary disorders in males, whereas changed basal and cyclic secretion of LH and FSH in females is caused by disordered activity of the LH-RH production and receptor binding at the level of the hypothalamo-pituitary complex.
Neuroendocrine control of the pituitary gonadotropic function in experimental diabetes