The impact of altered insulin-like growth factor-I secretion on the neuroendocrine and testicular functions

There is unequivocal evidence that the biosynthesis and secretion of gonadotropins by the pituitary gland is controlled by the hypothalamic GnRH and the function of the testis is mainly regulated by FSH and LH. However, a number of investigations have suggested the role of other hormones/factors, including insulin-like growth factor-I (IGF-I) in the control of pituitary and gonadal functions. The role of growth hormone (GH) and IGF-I is poorly investigated in humans. In animals with altered IGF-I secretion, the gonadotropin and androgen secretions are affected. Similarly, there is evidence that fertility, the onset of puberty and sexual maturation are affected in some patients with Laron syndrome and in acromegaly. In this minireview, we have presented some data obtained in humans and also included results from several experimental models with altered GH/IGF-I secretion, in the hope that the results from animals will possibly help in understanding the important role of IGF-I in the control of neuroendocrine-testicular function in humans.