The Pituitary-Bone Connection

This chapter discusses the interaction of each pituitary hormone with bone and the potential it holds in understanding and treating osteoporosis. The discovery of glycoprotein hormones and their direct regulation of bone help explain some of the inconsistencies of older models that assumed that pituitary signaling was mediated entirely via endocrine organs through steroid-family signals. Important direct responses include actions of growth hormone (GH), thyroid stimulating hormone (TSH), follicle stimulating hormone (FSH), adrenocorticotrophic hormone (ACTH), and oxytocin (OT) in bone. It is important, in evaluating these new signaling mechanisms, to consider that the skeletal responses may or may not have similar mechanisms to the responses of the traditional endocrine targets, and that the signals may vary in importance due to secondary endocrine and paracrine control. The discovery of direct skeletal responses of pituitary hormones nevertheless offers a new set of therapeutic opportunities.