Our findings suggest that serum sclerostin levels are regulated by both estrogens and PTH in postmenopausal women. These findings need to be explored further in larger prospective studies.

Osteoporosis is a skeletal disorder characterized by decreased bone mineral density and compromised bone strength predisposing to an increased risk of fractures. Although idiopathic osteoporosis is the most common form of osteoporosis, secondary factors may contribute to the bone loss and increased fracture risk in patients presenting with fragility fractures or osteoporosis. Several medical conditions and medications significantly increase the risk for bone loss and skeletal fragility. This review focuses on some of the common causes of osteoporosis, addressing the underlying mechanisms, diagnostic approach and treatment of low bone mass in the presence of these conditions.

Clinicians need to have a high index of suspicion for endocrine abnormalities in people with HIV as they can be potentially life threatening if untreated. Endocrine evaluation should be pursued as in the general population, with focus on prevention, early detection and treatment to improve quality of life and longevity.

Raloxifene, but not bisphosphonates, significantly suppressed circulating sclerostin concentration, suggesting that sclerostin may mediate the action of estrogen on bone metabolism, independently of their anti-resorptive effects.

We examined the effects that ovariectomy had on sclerostin mRNA and protein levels in the bones of 8-week-old mice that were either sham-operated (SHAM) or ovariectomized (OVX) and then sacrificed 3 or 6 wks. later. In this model bone loss occurred between 3 and 5 wks. Post-surgery. In calvaria OVX significantly decrease sclerostin mRNA levels at 6 wks. post-surgery (by 52%) but had no significant effect at 3 wks. In contrast, sclerostin mRNA levels were significantly lower in OVX femurs at 3 wks. post-surgery (by 53%) but equal to that of SHAM at 6 wks. The effects of OVX on sclerostin were not a global response of osteocytes since they were not mimicked by changes in the mRNA levels for 2 other relatively osteocyte-specific genes: DMP-1 and FGF-23. Sclerostin protein decreased by 83% and 60%, respectively at 3 and 6 wks. post-surgery in calvaria and by 38% in lumbar vertebrae at 6 wks. We also detected decreases in sclerostin by immunohistochemistry in cortical osteocytes of the humerus at 3 wks. post-surgery. However, there were no significant effects of OVX on sclerostin protein in femurs or on serum sclerostin at 3 and 6 wks. post-surgery. These results demonstrate that OVX has variable effects on sclerostin mRNA and protein in mice, which are dependent on the bones examined and the time after surgery. Given the discrepancy between the effects of OVX on serum sclerostin levels and sclerostin mRNA and protein levels in various bones, these results argue that, at least in mice, serum sclerostin levels may not accurately reflect changes in the local production of sclerostin in bones. Additional studies are needed to evaluate whether this is also the case in humans.