Osteoporosis in otherwise healthy perimenopausal and early postmenopausal women: physical and biochemical characteristics

Current knowledge of bone-derived factor osteocalcin: its role in the management and treatment of diabetes mellitus, osteoporosis, osteopetrosis and inflammatory joint diseases

Osteocalcin (OC) is the most abundant non-collagenous and osteoblast-secreted protein in bone. It consists of two forms such as carboxylated OC (cOC) and undercarboxylated OC (ucOC). While cOC promotes bone mineralization and increases bone strength, ucOC is regarded an endocrinologically active form that may have several functions in multiple end organs and tissues. Total OC (tOC) includes both of these forms (cOC and ucOC) and is considered a marker of bone turnover in clinical settings. Most of the data on OC is limited to preclinical studies and therefore may not accurately reflect the situation in clinical conditions. For the stated reason, the aim of this review was not only to summarize current knowledge of all forms of OC and characterize its role in diabetes mellitus, osteoporosis, osteopetrosis, inflammatory joint diseases, but also to provide new interpretations of its involvement in the management and treatment of aforementioned diseases. In this context, special emphasis was placed on available clinical trials. Significantly lower levels of tOC and ucOC could be associated with the risk of type 2 diabetes mellitus. On the contrary, tOC level does not seem to be a good indicator of high bone turnover status in postmenopausal osteoporosis, osteoarthritis and rheumatoid arthritis. The associations between several pharmacological drugs used to treat all disorders mentioned above and OC levels have also been provided. From this perspective, OC may serve as a medium through which certain medications can influence glucose metabolism, body weight, adiponectin secretion, and synovial inflammation.

A meta-analysis of serum osteocalcin level in postmenopausal osteoporotic women compared to controls

Background

Circulatory osteocalcin (OC) has been widely used as a biomarker to indicate bone turnover status in postmenopausal osteoporosis (PMO). However, the change of serum OC (sOC) level in PMO cases compared to postmenopausal controls remains controversial.

Methods

We searched the online database of PubMed and Cochrane Library. A meta-analysis of case-control studies was performed to compare the pooled sOC level between PMO patients and postmenopausal controls. Subgroup analysis according to potential confounding factors (different OC molecules and regions of the study population) was also performed.

Results

Ten case-control studies with 1577 postmenopausal women were included in this meta analysis. We found no significant difference in the pooled sOC level [mean difference (MD) = 1.84, 95% confidence interval (CI): (− 1.49, 5.16), p = 0.28] between PMO patients and controls. Subgroup analysis also revealed no significant difference in intact OC [MD = 1.76, 95%CI: (− 1.71, 5.23), p = 0.32] or N-terminal mid-fragment of the OC molecule [MD = 0.67, 95%(− 5.83, 7.18), p = 0.84] between groups. For different regions, no significant difference in sOC was found in Asian population between cases and controls [MD = -0.06, 95%(− 6.02, 5.89), p = 0.98], while the pooled sOC level was significantly higher in European PMO cases than controls [MD = 3.15, 95%(0.90, 5.39), p = 0.006].

Conclusions

Our analysis revealed no significant difference in sOC level between PMO cases and controls according to all the current eligible studies. OC molecules are quite heterogeneous in the circulation and can be influenced by glucose metabolism. Therefore, sOC is currently not a good indicator for the high bone turnover status in PMO. More trials with standardized methodologies for the evaluation of circulatory OC are awaited to update our current findings.

Validity of self-reported osteoporosis in mid-age and older women

The validity of self-reported osteoporosis is often questioned, but validation studies are lacking. We validated self-reported prevalence and incidence of osteoporosis against self-reported and administrative data on medications. The concurrent validity was moderate to good for self-reported prevalent osteoporosis, but only poor to moderate for self-reported incident osteoporosis in mid-age and older women, respectively. Construct validity was acceptable for self-reported prevalent but not for incident osteoporosis.

INTRODUCTION

The validity of self-reported osteoporosis is often questioned, but validation studies are lacking. The aim was to examine the validity of self-reported prevalence and incidence of osteoporosis against self-reported and administrative data on medications.

METHODS

Data were from mid-age (56-61 years in 2007) and older (79-84 years in 2005) participants in the Australian Longitudinal Study on Women's Health. Self-reported diagnosis was compared with medication information from (1) self-report (n(mid) = 10,509 and n(old) = 7,072), and (2) pharmaceutical prescription reimbursement claims (n(mid) = 6,632 and n(old) = 4,668). Concurrent validity of self-report was examined by calculating agreement, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). Construct validity was tested by examining associations of self-reported diagnosis with osteoporosis-related characteristics (fracture, weight, bodily pain, back pain, and physical functioning).

RESULTS

Agreement, sensitivity and PPV of self-reported prevalent diagnosis were higher when compared with medication claims (mid-age women: kappa = 0.51, 95% confidence interval [CI] = 0.46-0.56; older women: kappa = 0.65, 95% CI = 0.63-0.68) than with self-reported medication (mid-age women: kappa = 0.41, 95% CI = 0.37-0.45; older women: kappa = 0.57, 95% CI = 0.55-0.59). Sensitivity, PPV and agreement were lower for self-reported incident diagnosis (mid-age women: kappa = 0.39, 95% CI = 0.32-0.47; older women: kappa = 0.55, 95% CI = 0.51-0.61). Statistically significant associations between self-reported diagnosis and at least four of five characteristics were found for prevalent diagnosis in both age groups and for incident diagnosis in older women.

CONCLUSIONS

The concurrent validity was moderate to good for self-reported prevalent osteoporosis, but only poor to moderate for self-reported incident osteoporosis in mid-age and older women, respectively. Construct validity was acceptable for self-reported prevalent but not for incident osteoporosis.

Calcitriol restores renovascular function in estrogen-deficient rats through downregulation of cyclooxygenase-2 and the thromboxane-prostanoid receptor

Cardiovascular risks increase in postmenopausal women. While vitamin D is supplemented for osteoporosis, it is not known whether it protects renal arterial function during estrogen deficiency. Here we measured changes in renovascular reactivity induced by ovariectomy in rats and examined whether calcitriol, the most active form of vitamin D, was able to correct such changes. The impairment of endothelium-dependent relaxation in renal arteries from ovariectomized rats was effectively reversed by long-term calcitriol treatment. It was also corrected by acute exposure to cyclooxygenase-2 (COX-2) inhibitors and a thromboxane-prostanoid receptor antagonist, respectively. Calcitriol normalized the overexpression of COX-2 and thromboxane-prostanoid receptors in intralobal renal artery segments and aortic endothelial cells isolated from ovariectomized rats. In vitro exposure of the arterial segments to calcitriol for 12 h improved relaxation and downregulated thromboxane-prostanoid receptors. The attenuated nitric oxide production in ovariectomized rat aortic endothelial cells was restored following a 12-h treatment with calcitriol, COX-2 inhibition, or thromboxane-prostanoid receptor antagonism. Thus, impaired endothelium-dependent renal artery relaxation in ovariectomized rats is mediated largely through increased activity and expression of COX-2 and the thromboxane-prostanoid receptor. Calcitriol restores endothelial function through downregulating both signaling proteins during estrogen deficiency.

Bone Turnover Markers Relations to Postmenopausal Osteoporosis

Osteoporosis is a systemic disease characterized by low bone mass and high bone turnover markers in postmenopausal women (PM). The relationship between biochemical bone markers C-telopeptides of type 1 collagen (CTX) and osteocalcin (OC), and bone mineral density (BMD) in the postmenopausal period was examined in 104 PM women divided into three groups according to their BMD: group A - control PM with normal bone density, group B - osteopenic PM and group C - osteoporotic PM. Mean CTX values were highest in group C (0.54±0.24 ng/mL) compared to group B (0.44±0.21 ng/mL) (p<0.0001), and group A (0.33±0.13 ng/mL) (p<0.029). Mean OC levels in group C (26.83±9.91 ng/mL) were significantly higher compared to group A (20.47±7.03 ng/mL) (p<0.011) but not significantly higher compared to group B (24.11±8.38 ng/mL) (p>0.05). Postmenopause duration was longest in group C (13.1±8.31 yrs) compared to group B (9.6±6.24 yrs), and group A (8.15±6.86 yrs). Postmenopausal women developed osteoporosis with longer menopause duration. PM osteoporotic women were characterized by increased levels of bone turnover markers indicating increased rate of bone remodeling, which resulted in excessive bone resorption, and loss of bone mass. Long-term persistence of high bone resorption marker CTX, insufficiently compensated with bone formation marker OC, enabled osteoporosis development.

Impact of total versus subtotal thyroidectomy on calcium metabolism and bone mineral density in premenopausal women

Objective:

This study aimed to compare the impact of total versus subtotal thyroidectomy on calcium metabolism and bone mineral density in euthyroid, premenopausal women.

Subjects:

The study included 24 premenopausal women who had undergone total (n = 10) or subtotal (n = 14) thyroidectomy and who were receiving nonsuppressive doses of thyroxine. The median post-operative period was four years. We determined, in all patients, the following parameters associated with calcium metabolism: total serum calcium, inorganic phosphate, intact parathormone, calcitonin and alkaline phosphatase. The bone mineral density of the spine and hip were measured using a Hologic QDR 4500C bone densitometer and were compared with controls matched for age and peak bone mineral density (using the t-test).

Results:

The measured calcium metabolism parameters were normal in all patients, and none had osteoporosis. There was no significant difference in the bone mineral density measurements for the spine and hip, comparing patients who had undergone total versus subtotal thyroidectomy (using the t-test).

Conclusion:

The impact of total thyroidectomy on bone mineral metabolism is not significantly different from that of subtotal thyroidectomy, in premenopausal women with normal thyroid-stimulating hormone values.

The amino- and carboxyterminal cross-linked telopeptides of collagen type I, NTX-I and CTX-I: a comparative review

Bone diseases such as osteoporosis or bone metastases are a continuously growing problem in the ageing populations across the world. In recent years, great efforts have been made to develop specific and sensitive biochemical markers of bone turnover that could help in the assessment and monitoring of bone turnover. The amino- and carboxyterminal cross-linked telopeptides of type I collagen (NTX-I and CTX-I, respectively) are two widely used bone resorption markers that attracted great attention due to their relatively high sensitivity and specificity for the degradation of type I collagen, and their rapid adaptation to automated analyzers. However, the clinical performance of both markers differs significantly depending on the clinical situation. These differences have caused considerable confusion and uncertainty. If used correctly, both markers have great potential to improve the management of many bone diseases. We here review the biochemistry, analytical background and clinical performance of NTX-I and CTX-I, as documented in the accessible literature until March 2008.

Genetic and constitutional influences on bone turnover markers: a study of male twin pairs

Biochemical markers of bone turnover originating from type I procollagen synthesis or type I collagen breakdown were examined in men using a classic twin study design based on monozygotic (MZ) and dizygotic (DZ) twins. The aim was to estimate the influence of heredity (genes and shared family childhood elements) and constitutional factors in determining procollagen type I amino-terminal propeptide (PINP), type I collagen carboxy-terminal telopeptide (ICTP), and urinary amino-terminal type I collagen telopeptide (NTx) marker levels in a sample of in 98 MZ and 108 DZ male twin pairs. We are not aware of any prior studies conducted in men that address the influence of genetic factors on bone turnover marker variability. The findings support a dominant role for heredity in the variation of bone resorption marker levels in men, with additive genetic effects explaining two-thirds of the variance in the bone resorption markers NTx and ICTP. Genetic factors may contribute less for PINP, a marker of bone formation. The genetic loci influencing PINP or NTx and body weight/disc axial area, although related in part, appeared to be largely independent, indicating that genetic effects on bone turnover are unlikely to be to a large degree a result of genetic regulation of individual body weight.