Sclerostin measurement in human disease: Validity and current limitations

Sclerostin a potent regulator of bone formation, is an antagonist of the Wnt-signaling pathway. The advent of assays to measure circulating sclerostin has enabled research to be performed with the aim to understand the potential role of circulating sclerostin as a pathophysiological marker in a variety of clinical settings. At this time, however, assays to measure circulating sclerostin are still relatively new and have not demonstrated consistent internal agreement in addition to which there are differences between serum and plasma levels. Nevertheless, measurement of sclerostin in the circulation has the potential to reflect the dynamics of bone formation with particular reference to situations in which osteocytes, the major source of circulating sclerostin, may be perturbed. Because of technical uncertainties regarding sclerostin assays that are currently available, circulating sclerostin measurements should be interpreted cautiously with attention to reference ranges for each assay and whether or not the measurement is made in serum or plasma.

Therapy of Hypoparathyroidism With PTH(1-84): A Prospective Six Year Investigation of Efficacy and Safety

CONTEXT

Human recombinant (rh)PTH(1-84) was recently approved for the treatment of refractory hypoparathyroidism, based upon a short-term phase 3 clinical trial. Long-term data are needed, because no time limit was placed on the treatment period.

OBJECTIVE

We studied the effect of long-term rhPTH(1-84) treatment in hypoparathyroidism for up to 6 years.

DESIGN

Prospective open-label study.

SETTING

Referral center.

PATIENTS

A total of 33 subjects with hypoparathyroidism.

INTERVENTIONS

rhPTH(1-84) treatment was initiated at a starting dose of 100 μg every other day for 6 years. Due to the availability of new dosages during the 6-year time period of the study, the dose could be and was adjusted for most patients to a daily dosing regimen.

MAIN OUTCOME MEASURES

Supplemental calcium and vitamin D requirements, serum and urinary calcium (monthly for 6 mo and then biannually), serum phosphorus, bone turnover markers, and bone mineral density (BMD) biannually.

RESULTS

Treatment with rhPTH(1-84) progressively reduced supplemental calcium requirements over 6 years by 53% (P < .0001) and 1,25-dihydroxyvitamin D requirements by 67% (P < .0001). Sixteen subjects (48%) were able to eliminate 1,25-dihydroxyvitamin D supplementation completely. Serum calcium concentration remained stable, and urinary calcium excretion fell. Lumbar spine BMD increased (3.8 ± 1%, P = .004) as did total hip BMD (2.4 ± 1%, P = .02), whereas femoral neck BMD remained stable and the distal one third radius decreased (-4.4 ±1%, P < .0001). Bone turnover markers increased significantly, reaching a 3-fold peak above baseline values at 1 year and subsequently declining but remaining higher than pretreatment values. Hypercalcemia was uncommon (12 episodes over 6 y; 2.5% of all values).

CONCLUSIONS

Long-term, continuous therapy of hypoparathyroidism for 6 years with rhPTH(1-84) is associated with reductions in supplemental calcium and calcitriol requirements, stable serum calcium concentration, and reduced urinary calcium excretion. The safety profile remains good. These data represent the longest experience with the therapeutic use of PTH for any condition and demonstrate its long-term efficacy and safety in hypoparathyroidism.

Presentation of Hypoparathyroidism: Etiologies and Clinical Features

CONTEXT

Understanding the etiology, diagnosis, and symptoms of hypoparathyroidism may help to improve quality of life and long-term disease outcomes. This paper summarizes the results of the findings and recommendations of the Working Group on Presentation of Hypoparathyroidism.

EVIDENCE ACQUISITION

Experts convened in Florence, Italy, in May 2015 and evaluated the literature and recent data on the presentation and long-term outcomes of patients with hypoparathyroidism.

EVIDENCE SYNTHESIS

The most frequent etiology is surgical removal or loss of viability of parathyroid glands. Despite precautions and expertise, about 20-30% of patients develop transient and 1-7% develop permanent postsurgical hypoparathyroidism after total thyroidectomy. Autoimmune destruction is the main reason for nonsurgical hypoparathyroidism. Severe magnesium deficiency is an uncommon but correctable cause of hypoparathyroidism. Several genetic etiologies can result in the loss of parathyroid function or action causing isolated hypoparathyroidism or a complex syndrome with other symptoms apart from those of hypoparathyroidism or pseudohypoparathyroidism. Neuromuscular signs or symptoms due to hypocalcemia are the main characteristics of the disease. Hyperphosphatemia can contribute to major long-term complications such as ectopic calcifications in the kidney, brain, eye, or vasculature. Bone turnover is decreased, and bone mass is increased. Reduced quality of life and higher risk of renal stones, renal calcifications, and renal failure are seen. The risk of seizures and silent or symptomatic calcifications of basal ganglia is also increased.

CONCLUSIONS

Increased awareness of the etiology and presentation of the disease and new research efforts addressing specific questions formulated during the meeting should improve the diagnosis, care, and long-term outcome for patients.

How Long to Treat with Denosumab

Chronic diseases typically require long-term treatment. Osteoporosis is a chronic disease in which fracture risk is high, and treatment is required to prevent fragility fractures. Denosumab is a fully human monoclonal antibody that inhibits RANK ligand, a powerful bone-resorbing cytokine. It is approved for individuals with osteoporosis who are at high risk for fracture. Clinical trial results confirm that denosumab is effective over the long term and has an excellent safety profile. In patients at high risk for osteoporotic fracture, therefore, long-term treatment with denosumab appears to present an attractive benefit profile.

Bone markers and osteoporosis therapy

Several factors are involved in determining bone quality including bone density, bone turnover, the extent of trabecular bone connectivity, cortical porosity and geometry. Metabolically active and in a continuous process of remodeling, approximately 20% of bone tissue is renewed annually. Bone turn over markers (BTM) are frequently used in clinical trials and to provide valid information about the effectiveness of osteoporosis treatment, reflecting the state of bone metabolism and its response to treatment, although they are not useful alone to estimate bone loss. In this review the behavior of BTM from different clinical trials or different osteoporotic drugs will be addressed.

Prevalence of kidney stones and vertebral fractures in primary hyperparathyroidism using imaging technology

CONTEXT

The fourth International Workshop on the Management of Asymptomatic Primary Hyperparathyroidism (PHPT) has recently suggested that skeletal and renal imaging be routinely conducted. So far, no study has systematically assessed this issue.

OBJECTIVE

The objective was to evaluate the prevalence of kidney stones (KS) and vertebral fractures (VFs) in a cohort of patients with PHPT utilizing noninvasive imaging technology.

DESIGN

This was a prospective study evaluating patients consecutively diagnosed with PHPT in a single center over a 5-year period (2009-2013).

SETTING

The setting was a referral center.

PATIENTS

There were a total of 140 patients with PHPT (127 women [18 premenopausal and 109 postmenopausal] and 13 men; mean age, 63.2 ± 11 y).

MAIN OUTCOMES MEASURES

Main outcome measures were the prevalence of KS by abdominal ultrasound, osteoporosis by dual-energy x-ray absorptiometry (DXA) (lumbar spine, femoral neck, total hip, and distal 1/3 radius), and VFs by vertebral spine x-ray, with attention to those categorized as symptomatic or asymptomatic.

RESULTS

Fifty-five percent of all subjects had KS by ultrasound, 62.9% had osteoporosis by T-score at any site, and 35.1% had VFs by x-ray. There was no difference in the incidence of VFs and densitometric osteoporosis between symptomatic and asymptomatic patients (VFs, 34.4 vs 34.7%; osteoporosis by DXA, 59.4 vs 65.8%), whereas more KS were detected in symptomatic (78%) than asymptomatic (35.5%). Twenty-two percent of patients classified as asymptomatic at baseline without osteoporosis by DXA were found to have KS and/or VFs.

CONCLUSIONS

Nephrolithiasis and VFs are common in asymptomatic subjects with PHPT. The results provide evidence in support of recent recommendations that a more proactive approach be taken to detect silent bone and stone disease in asymptomatic PHPT.

Diagnosis of asymptomatic primary hyperparathyroidism: proceedings of the Fourth International Workshop

OBJECTIVE

Asymptomatic primary hyperparathyroidism (PHPT) is a common clinical problem. The purpose of this report is to provide an update on the use of diagnostic tests for this condition in clinical practice.

PARTICIPANTS

This subgroup was constituted by the Steering Committee to address key questions related to the diagnosis of PHPT. Consensus was established at a closed meeting of the Expert Panel that followed.

EVIDENCE

Each question was addressed by a relevant literature search (on PubMed), and the data were presented for discussion at the group meeting.

CONSENSUS PROCESS

Consensus was achieved by a group meeting. Statements were prepared by all authors, with comments relating to accuracy from the diagnosis subgroup and by representatives from the participating professional societies.

CONCLUSIONS

We conclude that: 1) reference ranges should be established for serum PTH in vitamin D-replete healthy individuals; 2) second- and third-generation PTH assays are both helpful in the diagnosis of PHPT; 3) normocalcemic PHPT is a variant of the more common presentation of PHPT with hypercalcemia; 4) serum 25-hydroxyvitamin D concentrations should be measured and, if vitamin D insufficiency is present, it should be treated as part of any management course; 5) genetic testing has the potential to be useful in the differential diagnosis of familial hyperparathyroidism or hypercalcemia.

Parathyroid hormone 1-84 alters circulating vascular endothelial growth factor levels in hypoparathyroidism

CONTEXT

We previously reported on four patients treated with PTH(1-84) who recovered from postoperative hypoparathyroidism many years after onset. Because vascular endothelial growth factor (VEGF) has been shown to be necessary for the induction of PTH-mediated angiogenesis, we postulated a possible role for VEGF in the recovery of parathyroid function in these subjects.

OBJECTIVE

Our objective was to measure VEGF levels in subjects with hypoparathyroidism who regained parathyroid gland function and matched controls.

SETTING AND DESIGN

Subjects with hypoparathyroidism who regained parathyroid gland function were each matched to two hypoparathyroid controls by postoperative etiology, age (within 5 y), menopausal status, and duration of hypoparathyroidism. We measured serum VEGF levels at baseline and through 48 months of PTH(1-84) therapy.

RESULTS

VEGF levels increased after the initiation of PTH(1-84) therapy for the entire cohort, from 309.7 ± 162 pg/ml at baseline to 380.2 ± 178 pg/ml at 12 months (P = .03). Levels trended downward thereafter. There were no significant differences in VEGF levels between the subjects with recovery of parathyroid function and the matched controls.

CONCLUSIONS

PTH(1-84) alters serum VEGF levels in subjects with hypoparathyroidism. Additional investigation is necessary to understand the mechanisms by which some subjects with postoperative hypoparathyroidism recover parathyroid gland function.

Comparison of two commercially available ELISAs for circulating sclerostin

This study investigates the performance and correlation of sclerostin measurements by two commercially available sclerostin ELISAs from TECOmedical and Biomedica. We found that the correlation between the results of two sclerostin assays is strong.

INTRODUCTION

Circulating sclerostin levels may provide insight into the pathophysiology of metabolic bone diseases such as osteoporosis. However, recent studies suggest that commercially available assays give different results. We compare the analytical performance of the two most used commercially available sclerostin ELISAs from TECOmedical and Biomedica.

METHODS

Sclerostin levels were assessed in 20 paired serum, EDTA, and heparin plasma convenience samples from hospitalized patients. In addition, sclerostin was measured in serum samples from 34 patients with metabolic bone diseases and from 10 patients with chronic kidney disease (CKD). Samples from three healthy donors were used to determine stability and intra- and inter- assay precision.

RESULTS

The average serum sclerostin concentration of all patients (n = 64) was 0.713 ± 0.58 ng/mL with the Biomedica assay and 0.734 ± 0.43 ng/mL with the TECO assay (p < 0.05). The results correlated strongly (r = 0.9; p < 0.0001), with Passing-Bablok regression showing a linear relationship but with a slight systematic and proportional difference between both assays. Sclerostin levels were about 30% higher in plasma than in serum for both assays, while no significant difference was seen between EDTA and heparin plasma. Intra- and inter- precision were <10% for TECO and <20% for Biomedica. Samples were stable for up to three freeze-thaw cycles with both assays.

CONCLUSIONS

The two commercially available ELISAs for measuring circulating levels of sclerostin are comparable. However, given the small but statistically significant systematic and proportional differences between both assays, results and reference ranges will be assay-specific. Results will also be specific to serum or plasma.

Update on romosozumab : a humanized monoclonal antibody to sclerostin

INTRODUCTION

Disorders with inactivating mutations of the SOST gene result in reduced or absent expression of sclerostin and are associated with high bone mass. Sclerostin is an important regulator of bone formation due to its inhibitory actions in the osteoanabolic Wnt signaling pathway. Advances in understanding the mechanisms of action of this signaling molecule have led to the development of a pharmacological inhibitor of sclerostin with potential clinical applications as an osteoanabolic drug for the treatment of osteoporosis.

AREAS COVERED

Romosozumab is the first humanized monoclonal sclerostin antibody to be tested in clinical trials. Similar to preclinical animal studies with sclerostin antibodies, initial clinical studies show that romosozumab increases bone formation and bone mineral density.

EXPERT OPINION

Blocking sclerostin action with romosozumab is a promising new therapeutic approach to osteoanabolic therapy of osteoporosis; efficacy and safety data on large controlled studies are awaited.

When, where and how osteoporosis-associated fractures occur: an analysis from the Global Longitudinal Study of Osteoporosis in Women (GLOW)

Objective

To examine when, where and how fractures occur in postmenopausal women.

Methods

We analyzed data from the Global Longitudinal Study of Osteoporosis in Women (GLOW), including women aged ≥55 years from the United States of America, Canada, Australia and seven European countries. Women completed questionnaires including fracture data at baseline and years 1, 2 and 3.

Results

Among 60,393 postmenopausal women, 4122 incident fractures were reported (86% non-hip, non-vertebral [NHNV], 8% presumably clinical vertebral and 6% hip). Hip fractures were more likely to occur in spring, with little seasonal variation for NHNV or spine fractures. Hip fractures occurred equally inside or outside the home, whereas 65% of NHNV fractures occurred outside and 61% of vertebral fractures occurred inside the home. Falls preceded 68–86% of NHNV and 68–83% of hip fractures among women aged ≤64 to ≥85 years, increasing with age. About 45% of vertebral fractures were associated with falls in all age groups except those ≥85 years, when only 24% occurred after falling.

Conclusion

In this multi-national cohort, fractures occurred throughout the year, with only hip fracture having a seasonal variation, with a higher proportion in spring. Hip fractures occurred equally within and outside the home, spine fractures more often in the home, and NHNV fractures outside the home. Falls were a proximate cause of most hip and NHNV fractures. Postmenopausal women at risk for fracture need counseling about reducing potentially modifiable fracture risk factors, particularly falls both inside and outside the home and during all seasons of the year.

Circulating sclerostin levels and markers of bone turnover in Chinese-American and white women

CONTEXT

Chinese-American women have bone microarchitectural features that confer greater bone stiffness compared to white women, but the physiology underlying these findings has not been investigated.

OBJECTIVE

The purpose of the study was to assess racial differences in serum sclerostin and bone turnover markers (BTMs), and to explore their associations with each other, volumetric bone mineral density (BMD), and bone microarchitecture in Chinese-American and white women.

DESIGN AND SETTING

We conducted a cross-sectional study at a university hospital.

PARTICIPANTS

We studied 138 women.

RESULTS

Serum osteocalcin was 19-28% lower in pre- and postmenopausal Chinese-American vs white women, respectively (both P < .01). C-Terminal telopeptide of type I collagen (CTX) level was 18-22% lower in pre- and postmenopausal Chinese-American vs white women (both P < .05). Pre- vs postmenopausal differences in osteocalcin and CTX were greater in white vs Chinese-American women. Sclerostin levels were similar in both races, but BTMs were differentially associated with sclerostin by race and menopausal status. BTMs were not correlated with sclerostin in Chinese-Americans. CTX and bone-specific alkaline phosphatase were positively associated with sclerostin (r = 0.353, r = 0.458; both P < .05) in white premenopausal women. In contrast, in postmenopausal white women, the associations of sclerostin with amino-terminal propeptide of type I procollagen, isoform 5b of tartrate-resistant acid phosphatase, and CTX were negative (all P < .05). Adjusting for covariates, sclerostin was positively associated with areal BMD in both races.

CONCLUSIONS

Lower BTMs in Chinese-American women and greater age-related differences in BTMs among white women provide a physiological framework to account for racial differences in BMD, microarchitecture, and fracture.

Recovery of parathyroid hormone secretion and function in postoperative hypoparathyroidism: a case series

CONTEXT

Transient and permanent postoperative hypoparathyroidism are recognized complications of neck surgery. Postoperative hypoparathyroidism is usually considered permanent when it persists for 6 months; in rare cases, recovery of hypoparathyroidism through 1 year has been described. Recovery of hypoparathyroidism years after diagnosis has not previously been reported.

OBJECTIVE

We report four patients being treated with PTH(1-84) in a research protocol who recovered from postoperative hypoparathyroidism many years after onset.

METHODS

Recovery from hypoparathyroidism was established by: 1) serum calcium and PTH levels within the normal range off PTH(1-84) treatment for at least 1 week; 2) requirement for daily calcium supplementation reduced to ≤1 g; and 3) no supplemental active vitamin D therapy.

RESULTS

Hypoparathyroidism developed in three subjects after repeated neck surgery for primary hyperparathyroidism and in one subject after total thyroidectomy for Graves' disease. Parathyroid tissue autotransplant was performed in two of the four subjects. Two had undetectable PTH levels at study entry, whereas the other two subjects had detectable, although low, PTH levels. Hypoparathyroidism had been present for at least 8 years, and in one case for 16 years. The recovery of parathyroid function followed treatment with PTH(1-84) for 36 to 63 months.

CONCLUSIONS

Although it remains relatively rare, this report documents recovery of long-term postoperative hypoparathyroidism many years after the initial diagnosis. A potential role for exogenous PTH is intriguing with several plausible mechanisms.

Primary hyperparathyroidism is associated with abnormal cortical and trabecular microstructure and reduced bone stiffness in postmenopausal women

Typically, in the milder form of primary hyperparathyroidism (PHPT), now seen in most countries, bone density by dual-energy X-ray absorptiometry (DXA) and detailed analyses of iliac crest bone biopsies by histomorphometry and micro-computed tomography (µCT) show detrimental effects in cortical bone, whereas the trabecular site (lumbar spine by DXA) and the trabecular compartment (by bone biopsy) appear to be relatively well preserved. Despite these findings, fracture risk at both vertebral and nonvertebral sites is increased in PHPT. Emerging technologies, such as high-resolution peripheral quantitative computed tomography (HRpQCT), may provide additional insight into microstructural features at sites such as the forearm and tibia that have heretofore not been easily accessible. Using HRpQCT, we determined cortical and trabecular microstructure at the radius and tibia in 51 postmenopausal women with PHPT and 120 controls. Individual trabecula segmentation (ITS) and micro-finite element (µFE) analyses of the HRpQCT images were also performed to further understand how the abnormalities seen by HRpQCT might translate into effects on bone strength. Women with PHPT showed, at both sites, decreased volumetric densities at trabecular and cortical compartments, thinner cortices, and more widely spaced and heterogeneously distributed trabeculae. At the radius, trabeculae were thinner and fewer in PHPT. The radius was affected to a greater extent in the trabecular compartment than the tibia. ITS analyses revealed, at both sites, that plate-like trabeculae were depleted, with a resultant reduction in the plate/rod ratio. Microarchitectural abnormalities were evident by decreased plate-rod and plate-plate junctions at the radius and tibia, and rod-rod junctions at the radius. These trabecular and cortical abnormalities resulted in decreased whole-bone stiffness and trabecular stiffness. These results provide evidence that in PHPT, microstructural abnormalities are pervasive and not limited to the cortical compartment, which may help to account for increased global fracture risk in PHPT.

Bone turnover markers in primary hyperparathyroidism

Primary hyperparathyroidism is an endocrine disorder characterized by elevated or inappropriate normal levels of parathyroid hormone in a setting of hypercalcemia. The inclusion of calcium on the basic metabolic bone panel has allowed this disorder to be diagnosed even in the absence of symptoms. Nevertheless, the skeleton can be a target of excess parathyroid hormone activity even during its asymptomatic presentation. Bone turnover markers a surrogate index of the process of the remodeling process at the level of bone, and thus can be useful to monitor skeleton involvement in primary hyperparathyroidism.

Sclerostin: therapeutic horizons based upon its actions

Inactivating mutations of the SOST gene cause a reduction in sclerostin levels and are associated with high bone mass. The clinical phenotypes, sclerosteosis and van Buchem's disease, were described in 1950s. Much later, it was learned that both diseases are due to loss-of-function mutations in the SOST gene. As a regulator of an important osteoanabolic pathway, Wnt, inactivation of SOST leads to a stimulation of the pathway it regulates. The high bone mass in patients with either sclerosteosis or van Buchem's disease is associated with unusual skeletal strength; they do not fracture. Knowledge of this molecule and its actions led rather quickly to the development of anti-sclerostin antibodies that lead to marked increases in bone mass in both animals and human subjects. Blocking sclerostin action with anti-sclerostin antibodies is a promising new therapeutic approach to osteoanabolic therapy of osteoporosis.

Circulating sclerostin in disorders of parathyroid gland function

CONTEXT

Sclerostin, a protein encoded by the SOST gene in osteocytes and an antagonist of the Wnt signaling pathway, is down-regulated by PTH administration. Disorders of parathyroid function are useful clinical settings to study this relationship.

OBJECTIVE

The objective of the study was to evaluate sclerostin in two different disorders of parathyroid function, primary hyperparathyroidism and hypoparathyroidism, and to analyze the relationship between sclerostin and PTH, bone markers, and bone mineral density.

DESIGN

This is a cross-sectional study.

SETTING

The study was conducted at a clinical research center.

PATIENTS

Twenty hypoparathyroid and 20 hyperparathyroid patients were studied and compared to a reference control group.

RESULTS

Serum sclerostin was significantly higher in hypoparathyroid subjects than in hyperparathyroid subjects (P < 0.0001) and controls (P < 0.0001). PTH was negatively associated with sclerostin, achieving statistical significance in hypoparathyroidism (r = -0.545; P = 0.02). The bone turnover markers, cross-linked C-telopeptide of type I collagen (CTX) and amino-terminal propeptide of type I collagen (P1NP), were differently associated with sclerostin according to the parathyroid disorder. In primary hyperparathyroidism, bone turnover markers were associated negatively with sclerostin (for P1NP, r = -0.490; P = 0.03). In hypoparathyroidism, bone turnover markers were associated positively with sclerostin (for CTX, r = +0.571; P = 0.01). Although there was no significant correlation between bone mineral density and sclerostin in either parathyroid disorder, there was a significant positive relationship between sclerostin and bone mineral content in hypoparathyroidism.

CONCLUSIONS

The results are consistent with the hypothesis that PTH is a regulator of sclerostin in human disorders of parathyroid function. In addition, the results suggest that bone mineral content may be another factor that influences sclerostin.

Catabolic and anabolic actions of parathyroid hormone on the skeleton

PTH, an 84-amino acid peptide hormone synthesized by the parathyroid glands, is essential for the maintenance of calcium homeostasis.While in its traditional metabolic role, PTH helps to maintain the serum calcium concentration within narrow, normal limits and participates as a determinant of bone remodeling, more specific actions, described as catabolic and anabolic are also well known. Clinically, the catabolic effect of PTH is best represented by primary hyperparathyroidism (PHPT), while the osteoanabolic effect of PTH is best seen when PTH or its biological amino-terminal fragment [PTH(1-34)] is used as a therapy for osteoporosis. These dual functions of PTH are unmasked under very specific pathological (PHPT) or therapeutic conditions. At the cellular level, PTH favors bone resorption, mostly by affecting the receptor activator of nuclear factor κ-B (RANK) ligand (RANKL)-osteoprotegerin- RANK system, leading to an increase in osteoclast formation and activity. Increased bone formation due to PTH therapy is explained best by its ability to enhance osteoblastogenesis and/or osteoblast survival. The PTH-induced bone formation is mediated, in part, by a decrease in SOST/sclerostin expression in osteocytes. This review focuses on the dual anabolic and catabolic actions of PTH on bone, situations where one is enhanced over the other, and the cellular and molecular mechanisms by which these actions are mediated.

Cathepsin K: its skeletal actions and role as a therapeutic target in osteoporosis

Bone remodeling consists of two phases--bone resorption and bone formation--that are normally balanced. When bone resorption exceeds bone formation, pathologic processes, such as osteoporosis, can result. Cathepsin K is a member of the papain family of cysteine proteases that is highly expressed by activated osteoclasts. Cathepsin K readily degrades type I collagen, the major component of the organic bone matrix. With such a major role in the initial process of bone resorption, cathepsin K has become a therapeutic target in osteoporosis. The antiresorptive properties of cathepsin K inhibitors have been studied in phase I and phase II clinical trials. Phase III studies are currently underway for odanacatib, a selective cathepsin K inhibitor.

Therapy of osteoporosis in men with teriparatide

Osteoanabolic therapy is an attractive therapeutic option for men with osteoporosis because it directly stimulates bone formation, an action not shared by any antiresorptive drug. Teriparatide (recombinant human PTH(1-34)) and PTH(1-84) are available in many countries but PTH(1-84) is not available in the United States. Only teriparatide is approved for the treatment of osteoporosis in men. It is also indicated in glucocorticoid-induced osteoporosis. Teriparatide is associated with major gains in bone density at the lumbar spine and, to a lesser extent, in the hip regions. Vertebral and nonvertebral fractures are reduced in postmenopausal women treated with teriparatide. Fracture reduction data in men are less secure because the number of study subjects is small and the studies have not been powered to document this endpoint. Nevertheless, observational data in men suggest a reduction in vertebral fractures with teriparatide. Attempts to show further beneficial effects of teriparatide in combination with antiresorptive agents have not been demonstrated yet to be superior to monotherapy with teriparatide alone. The duration of therapy with teriparatide is limited to 2 years. Thereafter, it is necessary to treat with an antiresorptive drug to maintain, and perhaps increase, densitometric gains. Teriparatide is well tolerated with a good safety profile.