Parathyroid hormone in the treatment of involutional osteoporosis: back to the future

Understanding the mechanistic potential of plant based phytochemicals in management of postmenopausal osteoporosis

Postmenopausal osteoporosis, an epidemic disorder is defined as a loss in bone mineral density and a greater possibility of fractures in older women. It is a multifactorial disease under the control of various genetic, hormonal, and environmental factors. Insufficiency of estrogen hormone, leads to postmenopausal osteoporosis. Hormone replacement therapy (HRT), despite being the most effective treatment, it is associated with the risk of breast cancer and cardiovascular disorders. This review seeks to compile the most recent information on medicinal plants and natural compounds used to treat and prevent postmenopausal osteoporosis. Furthermore, the origin, chemical constituents and the molecular mechanisms responsible for this therapeutic and preventive effect are also discussed. Literature research was conducted using PubMed, Science direct, Scopus, Web of Science, and Google Scholar. Different plant extracts and pure compounds exerts their antiosteoporotic activity by inhibition of RANKL and upregulation of OPG. RANKL signaling regulates osteoclast formation, characterized by increased bone turnover and osteoprotegrin is a decoy receptor for RANKL thereby preventing bone loss from excessive resorption. In addition, this review also includes the chemical structure of bioactive compounds acting on NFκB, TNF α, RUNX2. In conclusion, we propose that postmenopausal osteoporosis could be prevented or treated with herbal products.

Treatment of postmenopausal osteoporosis: a literature-based algorithm for use in the public health care system

Bisphosphonates are considered first-line agents in the treatment of postmenopausal osteoporosis based on extensive experience of use, safety, and proven efficacy in reducing vertebral, non-vertebral and femur fractures. However, post-marketing reports based on the treatment of millions of patients/year over lengthy periods of time have revealed the occurrence of initially unexpected adverse effects, such as osteonecrosis of the jaw and atypical femoral fracture, leading to the restriction of treatment duration with bisphosphonates by global regulatory agencies. However, despite the association between these effects and bisphosphonates, this risk should be analyzed in the context of osteoporosis treatment, alongside the benefit of preventing osteoporotic fractures and their clinical consequences. Therefore, we consider it plausible to discuss the restriction to the use of bisphosphonates, possible indications for prolonged treatment and alternative therapies following the suspension of this drug class for patients with persistent high risk of fracture after initial treatment, especially considering the problems of public health funding in Brazil and the shortage of drugs provided by the government. Thus, to standardize the treatment of osteoporosis in the public health care system, we aim to develop a proposal for a scientifically-based pharmacological treatment for postmenopausal osteoporosis, establishing criteria for indication and allowing the rational use of each pharmacological agent. We discuss the duration of the initial bisphosphonate treatment, the therapeutic options for refractory patients and potential indications of other classes of drugs as first-choice treatment in the sphere of public health, in which assessing risk and cost effectiveness is a priority.

Efficacy and safety of currently marketed anti-osteoporosis medications

During the past 2 decades, many interventions were proven effective in the management of postmenopausal osteoporosis. The objective of an anti-osteoporosis treatment is to reduce fracture rates, ideally at all skeletal sites (i.e. spine, hip, and other non-spine). The armamentarium against osteoporosis includes anti-resorptive agents (i.e. bisphosphonates, selective estrogen receptor modulators and denosumab), bone-forming agents (i.e. peptides from the parathyroid hormone family) and one agent with a dual mechanism of action (i.e. strontium ranelate). All these medications combine antifracture efficacy with a reasonable benefit/risk profile. However, the choice of a particular chemical entity, in one individual patient is based on the knowledge and expertise of the physician. Prioritization of drugs should be based on the individual profile of the patient, the severity of osteoporosis and the specific contraindications, warnings and precautions of use of the various available medications.

Current, new and future treatments of osteoporosis

Osteoporosis as a common chronic disease is challenging human health. Although different therapeutic options are routinely used for prevention/treatment of osteoporosis, their side effects and benefits are under question. Increasing our knowledge about signaling pathways in bone and osteocytes as well as osteoblasts and osteoclasts will help us in designing new therapeutic modalities for osteoporosis. In the present study, all new therapeutic measures of osteoporosis have been reviewed. For this purpose, search engines like Pubmed, Web of Science, Scopus, Google Scholar were searched and all relevant articles were found. The study was limited to the year 1998-2010. Bisphosphonates are the cornerstone of osteoporosis treatment, but there are not enough relevant studies that investigated their equivalencies in comparison with each other or the other medications. Therefore, medication selection is empirical and subjective. Furthermore, no eminent study has compared certain combinations. There are new hopes for treatment of osteoporosis, which are more specific with less harm. Our results show that new and emerging therapies are more potent and target specified which more individualize osteoporosis treatment; however, more investigations on their safety and efficacy in comparison with current medications are highly recommended.

Progress in osteoporosis and fracture prevention: focus on postmenopausal women

In the past decade, we have witnessed a revolution in osteoporosis diagnosis and therapeutics. This includes enhanced understanding of basic bone biology, recognizing the severe consequences of fractures in terms of morbidity and short-term re-fracture and mortality risk and case finding based on clinical risks, bone mineral density, new imaging approaches, and contributors to secondary osteoporosis. Medical interventions that reduce fracture risk include sufficient calcium and vitamin D together with a wide spectrum of drug therapies (with antiresorptive, anabolic, or mixed effects). Emerging therapeutic options that target molecules of bone metabolism indicate that the next decade should offer even greater promise for further improving our diagnostic and treatment approaches.

Bone-forming agents in the management of osteoporosis

Women often consult for the first time after osteoporosis has already become established. Medications have therefore been developed which can stimulate bone formation, with the ultimate goal of restoring bone quantity and quality and reducing spinal and peripheral fractures to a greater extent than can be obtained with inhibitors of bone resorption. Peptides of the parathyroid hormone family, when given intermittently, increase the number and activity of osteoblasts, leading to an increase in bone mass and in an improvement in skeletal architecture. Teriparatide (1-34 parathyroid hormone, PTH) reduces vertebral and non-vertebral fractures at a dose of 20 microg/day given in subcutaneous daily injections. 1-84 PTH reduces vertebral fractures, but results on non-vertebral fractures are lacking. Strontium ranelate, suggested to uncouple bone formation from bone resorption, reduces vertebral, non-vertebral and hip fractures in osteoporotic patients aged >74 years. Reduction of a vertebral fracture has also been shown in osteopenic patients. Long-term (5-year) data are available on vertebral, non-vertebral, major non-vertebral and hip fractures in osteoporotic patients. Combination/sequential treatments using inhibitors of bone resorption and bone-forming agents have been assessed in a variety of regimens. Benefits from the use of bone-forming agents appear to be largely independent of previous treatment with inhibitors of bone resorption. After treatment with an anabolic agent, the use of anti-resorptive medications maintains the benefit of the former treatment. Concomitant use of an inhibitor of bone resorption and a stimulator of bone formation has not, so far, showed any additional benefit compared with each medication given alone.

Developments in the pharmacotherapeutic management of osteoporosis

During the last two decades, several medications have been granted a marketing authorisation for the management of osteoporosis. Bisphosphonates are the most widely prescribed drugs in this area, worldwide. Alendronate and risedronate are given daily or weekly and have demonstrated their ability to reduce fracture rates at the spine and hip. Ibandronate has demonstrated spine antifracture efficacy with intervals between dosings greater than weekly. New developments in this class include intravenous administration of ibandronate or zoledronate, once every three months or once yearly. Raloxifene, a selective estrogen-receptor modulator, reduces spine fractures and, in post-hoc analyses, non-spine fractures in high-risk subjects. New selective estrogen-receptor modulators, including lasofoxifene, bazedoxifene and arzoxifene, are expected to demonstrate antifracture efficacy at the hip level, whilst retaining the extra-skeletal benefits (such as in the breast) that are obtained with raloxifene. The peptides from the parathyroid hormone family are potent stimulators of bone formation. Teriparatide (1 - 34 amino acid fragment of the parathyroid hormone) reduces spine and non-spine fractures, an effect that is sustained for up to 30 months after the withdrawal of treatment. The intact hormone (1 - 84 amino acids) showed similar results on spine fractures, and more data are requested to evaluate its effect on non-spine or hip fractures. Strontium ranelate is suggested to be the first medication to uncouple bone formation from bone resorption. It has shown antifracture efficacy at all sites in a large number of postmenopausal women. New developments include: denosumab, an antibody against receptor activator of NF-kappaB ligand (RANKL); a cytokine that is responsible for osteoclastogenesis; and inhibitors of cathepsin K, a cysteine protease that is involved in the cleavage of collagen.