title: Reproductive hormones and bone.
abstract: Hypothalamic gonadotropin-releasing hormone (GnRH) stimulates secretion of pituitary luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which directly regulate ovarian function. Pituitary FSH can modulate osteoclast development, and thereby influence bone turnover. Pituitary oxytocin and prolactin effects on the skeleton are not merely limited to pregnancy and lactation; oxytocin stimulates osteoblastogenesis and bone formation, whereas prolactin exerts skeletal effects in an age-dependent manner. Cyclic levels of inhibins and estrogen suppress FSH and LH, respectively, and also suppress bone turnover via their suppressive effects on osteoblast and osteoclast differentiation. However, continuous exposure to inhibins or estrogen/androgens is anabolic for the skeleton in intact animals and protects against gonadectomy-induced bone loss. Alterations of one hormone in the hypothalamic-pituitary-gonadal (HPG) axis influence other bone-active hormones in the entire feedback loop in the axis. Thus, we propose that the action of the HPG axis should be extended to include its combined effects on the skeleton, thus creating the HPG skeletal (HPGS) axis.
authors.affiliation: Departments of Physiology and Biophysics and Orthopaedic Surgery, University of Arkansas for Medical Sciences, 4301 West Markham, Slot 505, Little Rock, AR, 72205, USA. Nicks.Kristy@mayo.edu
authors.forename: Kristy M
authors.initials: KM
authors.lastname: Nicks
authors.forename: Tristan W
authors.initials: TW
authors.lastname: Fowler
authors.forename: Dana
authors.initials: D
authors.lastname: Gaddy
mesh_terms: D015519:Bone Density / Q000502:physiology*; D016723:Bone Remodeling / Q000502:physiology*; D001842:Bone and Bones / Q000378:metabolism*; D042341:Gonadal Hormones / Q000378:metabolism*; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism*; D010024:Osteoporosis / Q000378:metabolism*; D010913:Pituitary-Adrenal System / Q000378:metabolism*
chemical_list: D042341:Gonadal Hormones