gnih and gnih receptor (gnih-r) mrna is expressed in the hypothalamus, pituitary, and ovaries. gnih expression is highest during proestrus and lowest during estrus, suggesting the estrus cycle influences release of the hormone. furthermore, gnih neuronal cell counts in multiple vertebrates fluctuate with an organism’s parental status. gnih cell count may also vary with breeding season in some species. for instance, european starlings (sturnus vulgaris) with greater reproductive success exhibited higher quantities of gnih-producing cells than did those that were less successful, but this effect did not appear until mid-breeding season.