Recombinant parathyroid hormone in the management of osteoporosis

The Emerging Roles of Endocrine Hormones in Different Arthritic Disorders

The relationship between endocrine hormones and the spectrum of rheumatic conditions has long been discussed in the literature, focusing primarily on sexual hormones, such as estrogens, androgens, prolactin (PRL). Estrogens are indeed involved in the pathogenesis of the main inflammatory arthritis thanks to their effects on the immune system, both stimulatory and inhibitory. The PRL system has been discovered in synovial tissue of rheumatoid arthritis (RA) and psoriatic arthritis (PsA), patients and has been propose as a new potential therapeutic target. Besides sexual hormones, in the last years scientific interest about the crosstalk of immune system with other class of hormones has grown. Hormones acting on the bone tissue (i.e. parathyroid hormone, vitamin D) and modulators of the Wnt pathway (i.e. Dickkopf-1) have been demonstrated to play active role in inflammatory arthritis course, defining a new field of research named osteoimmunology. PTH, which is one of the main determinants of Dkkopf-1, plays a crucial role in bone erosions in RA and a correlation between PTH, Trabecular Bone Score (TBS) and disease activity has been found in ankylosing spondylitis (AS). In PSA is under studying the interaction among IL-17 and bone metabolism. The purpose of this review is to discuss and summarize the recent data about the interaction between endocrine hormone and immune system in the main rheumatic disorders, covering in particular the role of bone-related hormones and cytokines. We will describe this relationship from a biochemical, diagnostic and therapeutic perspective, with a particular focus on RA, PsA and AS.

The effectiveness and safety of parathyroid hormone in fracture healing: A meta-analysis

The very large economic and social burdens of fracture-related complications make rapid fracture healing a major public health goal. The role of parathyroid hormone (PTH) in treating osteoporosis is generally accepted, but the effect of PTH on fracture healing is controversial. This meta-analysis was designed to investigate the efficacy and safety of PTH in fracture healing. The EMBASE, PubMed, and Cochrane Library databases were systematically searched from the inception dates to April 26, 2018. The primary randomized clinical trials comparing PTH treatment for fracture healing with placebo or no treatment were identified. We did not gain additional information by contacting the authors of the primary studies. Two reviewers independently extracted the data and evaluated study quality. This meta-analysis was executed to determine the odds ratio, mean difference, standardized mean difference, and 95% confidence intervals with random-effects models. In total, 8 randomized trials including 524 patients met the inclusion criteria. There were significant differences in fracture healing time, pain relief and function improvement. There were no significant differences in the fracture healing rate or adverse events, including light-headedness, hypercalcemia, nausea, sweating and headache, except for slight bruising at the injection site. We determined that the effectiveness and safety of PTH in fracture healing is reasonably well established and credible.

Effectiveness of Teriparatide on Fracture Healing: A Systematic Review and Meta-Analysis

Purpose

Nowadays, the efficacy of teriparatide in treating osteoporosis was widely accepted, but the discussion about using teriparatide to enhance fracture healing hasn’t come to an agreement. This meta-analysis was conducted to evaluate the effectiveness of teriparatide for fracture healing.

Methods

We searched PubMed, the Cochrane Library, and Embase in August 2016 for randomized controlled trials (RCTs) which concerned the treatment of teriparatide for fracture healing.

Results

Finally, a total of 380 patients were randomly assigned in the 5 trials included in this meta-analysis. There was a significant effectiveness with regards to function improvement in patients following fracture, however, there was no significant effectiveness with regards to time of radiographic fracture healing, fracture healing rate and reduction in pain.

Conclusions

This analysis showed that administration of teriparatide following fracture lacked the effectiveness for fracture healing. Moreover, teriparatide administration had no apparent adverse effects. These results should be interpreted with caution because of some clear limitations. If we want to confirm whether teriparatide improves fracture healing, more high-quality randomized controlled trials are needed.

Bone quality of the newest bone formed after two years of teriparatide therapy in patients who were previously treatment-naïve or on long-term alendronate therapy

The results of the present study, involving analysis of biopsies from patients who received teriparatide for 2 years and were previously either treatment-naïve or on long-term alendronate therapy, suggest that prior alendronate use does not blunt the favorable effects of teriparatide on bone quality.

INTRODUCTION

Examine the effect of 2 years of teriparatide (TPTD) treatment on mineral and organic matrix properties of the newest formed bone in patients who were previously treatment-naïve (TN) or on long-term alendronate (ALN) therapy.

METHODS

Raman and Fourier transform infrared microspectroscopic analyses were used to determine the mineral/matrix (M/M) ratio, the relative proteoglycan (PG) content, and the mineral maturity/crystallinity (MMC; determined by three methods: carbonate content, full width at half height of the v 1 PO4 band [FWHH], and wavelength at maxima of the v 1 PO4 band), as well as collagen maturity (ratio of pyridinoline/divalent cross-links), in paired iliac crest biopsies at trabecular, endosteal, and osteonal surfaces of newly formed bone in postmenopausal osteoporotic women who were previously either TN (n = 16) or receiving long-term ALN treatment (n = 24).

RESULTS

Trabecular M/M ratio increased and matrix content decreased significantly in the ALN pretreated group. Collagen maturity decreased in both patient groups. Endosteal M/M ratio increased significantly in the TN group. Trabecular M/M ratio was higher at endpoint in the ALN pretreated group than in the TN group. Overall, no changes from baseline were observed in PG content, except that PG content was higher in the ALN pretreated group than in the TN group at endosteal surfaces at endpoint. The ability of TPTD treatment to reduce MMC in both patient groups and at the different bone surfaces depended on the measurement tool (relative carbonate content or wavelength at maxima of the v 1 PO4 band). None of the changes in MMC were different between the two patient groups.

CONCLUSIONS

The results suggest some favorable impact of TPTD on bone mineral and organic matrix properties of in situ forming bone in terms of increased initial mineralization and decreased MMC and collagen maturity. Moreover, prior long-term ALN administration may have only limited influence on these properties in bone newly formed after 2 years of TPTD treatment.

Effects of one year daily teriparatide treatment on trabecular bone material properties in postmenopausal osteoporotic women previously treated with alendronate or risedronate

In the present work we examined the effect of teriparatide administration following bisphosphonate treatment on bone compositional properties by Raman and Fourier Transform Infrared Imaging (FTIR) microspectroscopic analysis. Thirty two paired iliac crest biopsies (before and after 1 year teriparatide) from sixteen osteoporotic women previously treated with either Alendronate (ALN) or Risedronate (RIS) and subsequently treated 12 months with teriparatide (TPTD) were analyzed at anatomical areas of similar tissue age in bone forming areas (within the fluorescent double labels). The outcomes that were monitored and reported were mineral to matrix ratio (corresponding to ash weight), mineral maturity (indicative of the mineral crystallite chemistry and stoichiometry, and having a direct bearing on crystallite shape and size), relative proteoglycan content (regulating mineralization commencement), and the ratio of two of the major enzymatic collagen cross-links (pyridinoline/divalent). Significant differences in mineral/matrix, mineral maturity/crystallinity, and collagen cross-link ratio bone quality indices after TPTD treatment were observed, indicating a specific response of these patients to TPTD treatment. Moreover differences between ALN and RIS treated patients at baseline in the collagen cross-link ratio were observed. Since tissue areas of similar tissue age were analyzed, these differences may not be attributed to differences in bone turnover.

Effects of 1 year of daily teriparatide treatment on iliacal bone mineralization density distribution (BMDD) in postmenopausal osteoporotic women previously treated with alendronate or risedronate

Anabolic treatment with teriparatide of postmenopausal osteoporotic patients previously treated with bisphosphonates is a new therapeutic approach. However, its effects on the bone mineralization density distribution (BMDD) are unknown. We studied paired transiliac bone biopsy samples taken before and after 1 year of treatment with recombinant human parathyroid hormone peptide 1-34 (teriparatide) from 16 osteoporotic women treated with either alendronate (priorALN) or risedronate (priorRIS) for at least 2 years and subsequently treated for 12 months with teriparatide. Cancellous (Cn.) and cortical (Ct.) BMDD values were measured using quantitative backscattered electron imaging. At baseline, BMDD values of priorALN and priorRIS women were similar and within the normal range. One year of teriparatide treatment caused significant effects on the BMDD. Analyzing changes from baseline for each bisphosphonate group separately, priorALN patients revealed increases in the portion of low mineralized bone areas (Cn.Ca(Low) +25.9%, Ct.Ca(Low) +62.0%, both p < .05) and Ct. heterogeneity of mineralization (Ct.Ca(Width) +22.8%, p < .001). PriorRIS patients showed increased mineralization heterogeneity (Cn.Ca(Width) +14.8%, p < .05, and Ct.Ca(Width) +15.8%, p < .001). Analysis of the influence of the prior bisphosphonate treatment showed that the BMDD response to 1 year of teriparatide treatment did not depend on the type of prior bisphosphonate. In consequence, priorALN and priorRIS groups were combined. The pooled groups revealed increased Cn.Ca(Width) and Ct.Ca(Width) (+10.7%, p < .01, and +19.6%, p < .001, respectively) as well as increased Cn.Ca(Low) and Ct.Ca(Low) (+18.2%, p < .05, and +36.6%, p < .01, respectively). In summary, our findings indicate a significant effect of teriparatide on BMDD when administered subsequent to a bisphosphonate in agreement with teriparatide's anabolic action.

1-Alkyl-4-phenyl-6-alkoxy-1H-quinazolin-2-ones: a novel series of potent calcium-sensing receptor antagonists

Parathyroid hormone (PTH) is an effective bone anabolic agent. However, only when administered by daily sc injections exposure of short duration is achieved, a prerequisite for an anabolic response. Instead of applying exogenous PTH, mobilization of endogenous stores of the hormone can be envisaged. The secretion of PTH stored in the parathyroid glands is mediated by a calcium sensing receptor (CaSR) a GPCR localized at the cell surface. Antagonists of CaSR (calcilytics) mimic a state of hypocalcaemia and stimulate PTH release to the bloodstream. Screening of the internal compound collection for inhibition of CaSR signaling function afforded 2a. In vitro potency could be improved >1000 fold by optimization of its chemical structure. The binding mode of our compounds was predicted based on molecular modeling and confirmed by testing with mutated receptors. While the compounds readily induced PTH release after iv application a special formulation was needed for oral activity. The required profile was achieved by using microemulsions. Excellent PK/PD correlation was found in rats and dogs. High levels of PTH were reached in plasma within minutes which reverted to baseline in about 1-2 h in both species.

Does osteocytic SOST suppression mediate PTH bone anabolism?

Parathyroid hormone (PTH) has bone anabolic activity when administered intermittently, affecting cells of the osteoblastic lineage at various stages, yet much remains to be learned about precisely how PTH promotes osteoblastic bone formation. Recent discoveries revealed that PTH causes transcriptional suppression of the osteocyte marker gene SOST, which encodes the potent secreted bone formation inhibitor, sclerostin. This review addresses whether osteocytes, terminally differentiated cells of the osteoblastic lineage, which are entrapped within the mineralized bone matrix, contribute to PTH-induced bone formation responses via regulation of sclerostin levels, and discusses recent evidence on how the bone anabolic responses elicited by intermittent PTH treatment or by sclerostin inhibition overlap and diverge.