The pituitary-bone axis in health and disease

The skeletal expression of pituitary glycoprotein receptors reflects that their function in endocrine control is evolutionarily more recent. Thus, growth hormone (GH), follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), prolactin (PRL), oxytocin (OXT), and vasopressin (AVP) all affect bone and, in mice, the haploin sufficiency of either the ligand and/or receptor often yields a skeletal phenotype with the primary target organ remaining unperturbed. Recognition and in-depth analysis of the mechanism of action of each pituitary hormone has improved the understanding of bone pathophysiology and opens new avenues for therapy. This chapter discusses the interaction of each pituitary hormone with bone and the potential it holds in understanding and treating osteoporosis. The presence of G-protein coupled receptors (GPCRs) in tissues other than traditional endocrine targets, such as the skeleton, and in some cases, coexistence of their ligands, comes as no surprise.