Skeletal morphofunctional considerations and the pituitary-thyroid axis

Regulated production of the pituitary hormone oxytocin from murine and human osteoblasts

Oxytocin (OT) is a primitive neurohypophyseal hormone that plays a primary and indispensible role in mammalian lactation. We have shown recently that OT also regulates bone remodeling, mainly bone formation, with remarkable sensitivity. We now show that OT, apart from its neurohypophyseal origin, is produced in abundance by both human and murine osteoblasts. Production of osteoblast OT is under the control of estrogen, which acts by activating the MAP kinase Erk. This non-genomic mechanism of estrogen action is in stark contrast to its genomic control of OT receptor (OTR) expression. We surmise that there is a local feed-forward loop in bone marrow through which the OT so produced from osteoblasts in response to estrogen acts upon its receptor to exert a potent anabolic action.

Commentary-FSH and bone 2010: evolving evidence

Bone loss due to menopause, natural or artificial, has been attributed solely to low estrogen. However, in a woman's life, the most precipitous bone loss begins 2 years prior to the last menstrual period, during which time estrogen levels are unperturbed whereas FSH is elevated. Our cell-based and mouse genetic studies have shown that FSH stimulates bone resorption by osteoclasts directly in a pituitary-bone axis, independently of the estrogen effect. On the basis of this and evolving clinical and scientific evidence, we propose that elevated FSH contributes to bone loss across the menopausal transition, particularly during late perimenopause. In the current issue of the European Journal of Endocrinology, Rendina et al. strengthen the view for a primary role of FSH signaling in the regulation of bone mass and bone remodeling in humans by demonstrating that an 'activating' polymorphism AA rs6166 causes low bone mass and high bone turnover.

ACTH protects against glucocorticoid-induced osteonecrosis of bone

We report that adrenocorticotropic hormone (ACTH) protects against osteonecrosis of the femoral head induced by depot methylprednisolone acetate (depomedrol). This therapeutic response likely arises from enhanced osteoblastic support and the stimulation of VEGF by ACTH; the latter is largely responsible for maintaining the fine vascular network that surrounds highly remodeling bone. We suggest examining the efficacy of ACTH in preventing human osteonecrosis, a devastating complication of glucocorticoid therapy.