in male vertebrates, gnih reduces testis size, lowers testosterone secretion, and increases the incidence of apoptosis in germ cells and sertoli cells of the seminiferous tubules. these gonadal changes, in addition to gnih and gnih-r mrna expression in the seminiferous tubules, sertoli cells, and spermatogonia, implicate function in spermatogenesis. in female vertebrates, high doses of gnih increases ovarian mass and produce follicle irregularities, such as vacuole formation in nuclei and distorted morphology. ovarian changes in response to gnih administration, as well as gnih/gnih-r mrna expression in granulosa cells and luteal cells in different stages of the estrus cycle, implicate function in development of follicles and atresia.