Relationship of age-related concentrations of serum FSH and LH with bone mineral density, prevalence of osteoporosis in native Chinese women

Peritoneal adhesion and angiogenesis in ovarian carcinoma are inversely regulated by hyaluronan: the role of gonadotropins

Ovarian carcinoma is the leading cause of death among gynecologic cancers. Although transformation of the outer ovarian epithelium was linked with ovulation, the disease is significantly more prevalent and severe in postmenopausal women. We postulated that menopause could augment ovarian cancer progression through the effects of gonadotropins on multifocal seeding to the mesothelial layer lining the peritoneum. This seeding is mediated by integrins as well as by CD44 interaction with hyaluronan (HA). Here, we report the effect of gonadotropins on HA synthesis and degradation and on peritoneal adhesion. A significant concentration- and time-dependent induction in expression levels of HA synthases (HASs) and hyaluronidases (Hyals) was observed in vitro on stimulation of human epithelial ovarian carcinoma cells by gonadotropins. Hormonal regulation of HA-mediated adhesion was manifested in vivo as well, by fluorescence microscopy of stained MLS multicellular tumor spheroids. The number of spheroids adhered to the mesothelium of ovariectomized CD-1 nude mice 9.5 hours after intraperitoneal insertion was significantly higher than in nonovariectomized mice. Inhibition of HA synthesis by 6-diazo-5-oxo-1-norleucine (DON) both in spheroids and ovariectomized mice significantly reduced the number of adhered spheroids. Thus, the change in the hormonal environment during menopause assists in HA-dependent adherence of ovarian cancer spheroids onto the peritoneum. However, HA is antiangiogenic and it can significantly suppress tumor progression. Accordingly, angiogenesis of the adhered spheroids was significantly elevated in DON-treated tumors. These results can explain the selective pressure that can lead to simultaneously increased tumor expression of both HASs and Hyals.

New horizons in skeletal physiology and pathophysiology

OBJECTIVE

To review new discoveries that revisit our current thinking on the genesis of osteoporosis using hypogonadal and thyrotoxic bone loss as examples.

METHODS

We focus on cell biologic, mouse genetic, and human studies that have established a direct action of the interior pituitary hormones follicle-stimulating hormone and thyrotropin on the skeleton and discuss emerging clinical evidence for a novel pituitary-bone axis in humans that bypasses master endocrine organs, namely the ovaries and thyroid gland.

RESULTS

The cataloguing of human mutations, the use of genetically modified mice that recapitulate human disease, and the rapid growth of genomic sciences have together had a profound impact on how basic research is translated into clinical practice. The skeleton has become a paradigm for the application of such advances to an extent that hitherto unrecognized physiologic and pathophysiologic findings have emerged. We propose that hypogonadal and thyrotoxic bone loss are not solely due to changes in the level of master hormones, but instead also arise from the direct action of anterior pituitary hormones on the skeleton.

CONCLUSIONS

We predict a pituitary-bone axis in which pituitary hormones bypass traditional endocrine targets to affect the skeleton directly with remarkable sensitivity. New therapeutic targets thus become a likely possibility.

Further evidence for direct pro-resorptive actions of FSH

We confirm that FSH stimulates osteoclast formation, function and survival to enhance bone resorption. It does so via the activation of a pertussis toxin-sensitive G(i)-coupled FSH receptor that we and others have identified on murine and human osteoclast precursors and mature osteoclasts. FSH additionally enhances the production of several osteoclastogenic cytokines, importantly TNFalpha, likely within the bone marrow microenvironment, to augment its pro-resorptive action. FSH levels in humans rise before estrogen falls, and this hormonal change coincides with the most rapid rates of bone loss. On the basis of accumulating evidence, we reaffirm that FSH contributes to the rapid peri-menopausal and early post-menopausal bone loss, which might thus be amenable to FSH blockade.

Age-related changes in biochemical markers of bone turnover and gonadotropin levels and their relationship among Chinese adult women

The relationship between the levels of gonadotropic hormones and bone metabolism in Chinese adult women is unclear. Our research shows that a significant positive correlation exists between the levels of gonadotropic hormones and various bone turnover indicators. Follicle-stimulating hormone (FSH) has been found to have a greater influence on all types of bone turnover indicator than luteinizing hormone (LH). Further, FSH has a greater influence on bone formation indicators than on bone resorption indicators.

INTRODUCTION

The aim of this study was to investigate the relationship between serum FSH and LH and biochemical markers of bone turnover in native Chinese adult women.

METHODS

We conducted a cross-sectional study of 694 healthy Chinese women aged between 20 and 82 years. Serum FSH, LH, bone-specific alkaline phosphatase (BAP), osteocalcin (OC), N-terminal telopeptides of type I collagen, C-terminal telopeptides of type I collagen, urinary NTX, urinary CTX, and urinary deoxypyridinoline (uDPD) were determined.

RESULTS

All types of bone turnover indicator were significantly positively correlated with FSH (r = 0.164-0.626, all P = 0.000) and LH (r = 0.130-0.618, all P = 0.013-0.000). The correlation coefficient between serum FSH and BAP was the highest (r = 0.626), and that between serum FSH and uDPD was the lowest (r = 0.164). The serum gonadotropic hormone levels were higher; concentrations of bone turnover indicators were higher. The extent of the influence of FSH on various bone turnover indicators was approximately seven to 20 times greater than that of LH on these indicators. FSH could explain 43% and 22% of the changes in BAP and OC, respectively; whereas, LH could explain only 2.1% and 1.1%, respectively. FSH could explain approximately 1.9-11.8% of the changes in bone resorption indicators; however, LH had almost no effect on them.

CONCLUSIONS

Gonadotropic hormone levels are correlated with the rate of bone turnover in Chinese women: the higher the serum gonadotropic hormone levels in circulation, the higher the levels of bone turnover indicators. FSH has a greater influence on all types of bone turnover indicator than LH; moreover, it has a greater influence on bone formation indicators than on bone resorption indicators.

Role of the pituitary-bone axis in skeletal pathophysiology

PURPOSE OF REVIEW

Embedded within textbooks for decades is the hard fact that releasing hormones from the anterior pituitary, namely, follicle-stimulating hormone, thyroid-stimulating hormone and adrenocorticotropic hormone, stimulate master hormone secretion from target endocrine organs. We propose a paradigm shift in endocrine physiology, which is that these hormones act by design on bone directly, also now considered an endocrine organ.

RECENT FINDINGS

Complementary investigations using mouse genetic and cell biological approaches reveal that follicle-stimulating hormone and thyroid-stimulating hormone act on bone cells directly to regulate bone remodeling and bone mass. Thyroid-stimulating hormone inhibits bone remodeling, whereas follicle-stimulating hormone stimulates it. We also find that the posterior pituitary hormone oxytocin is anabolic to the skeleton.

SUMMARY

An ambitious extrapolation is that a plurality of pituitary hormones acts in concert as part of a 'pituitary-bone' axis to regulate skeletal integrity in health and disease. When dysregulated master hormone levels during hypogonadism and hyperthyroidism cause altered pituitary hormone secretion through hypothalamic feedback, the latter hormones contribute to the skeletal loss.

New insights: elevated follicle-stimulating hormone and bone loss during the menopausal transition

We hypothesize that a rising follicle-stimulating hormone (FSH) level during the menopausal transition, even in the face of a normal estrogen level, contributes to increased bone resorption and profound bone loss that is accompanied by trabecular perforation and diminished bone strength. FSH has been shown to directly stimulate osteoclast formation and bone resorption, and our murine genetic studies indicate that the absence of FSH can, in part, protect against hypogonadal hyperresorption that causes bone loss. Furthermore, carefully conducted human studies, such as the Study of Women Across Nations (SWAN), indicate strong correlations between serum FSH levels and bone loss. Potential therapeutic implications include the development of antagonists to circulating FSH and its osteoclastic receptor.

The new frontier of bone formation: a breakthrough in postmenopausal osteoporosis?

OBJECTIVE

Osteoporosis is a chronic disease that accelerates after menopause in many women. Most of the pharmacologic attempts to control the disease, such as hormone therapy, have emphasized the constraint of bone resorption. Since recent years have witnessed important advances in the field of bone formation, this review aims to update the present knowledge on the mechanisms affecting osteoblastogenesis and on the therapeutic results achieved by recently approved drugs.

METHOD

We sought peer-reviewed, full-length basic and clinical articles published between 1995 and May 2008 using a PubMed search strategy, with the terms osteoporosis and osteoblast, osteoporosis and strontium ranelate, and osteoporosis and parathyroid hormone (PTH). This search was further supplemented by a hand-search of reference lists of selected review papers. After crossing-cleaning the reference lists, some 800 articles were selected. Articles on regulators of osteoblast differentiation and function, together with well-designed clinical studies, were surveyed.

RESULTS

A complex network of systemic and local factors regulates osteoblastogenesis. Advances in fracture protection have been published in clinical studies with PTH. Some investigators claim an anabolic effect for strontium ranelate, which also confers protection against fracture.

CONCLUSION

The control of bone formation offers new clinical potential. Stimulation of bone formation by PTH has translated into fracture protection. The action of strontium ranelate has been claimed to be mediated by some level of bone formation, but this hypothesis still needs clarification.