Current Pharmacological Options for the Management of Primary Hyperparathyroidism

Metabolic bone disorders and the promise of marine osteoactive compounds

Metabolic bone disorders and associated fragility fractures are major causes of disability and mortality worldwide and place an important financial burden on the global health systems. These disorders result from an unbalance between bone anabolic and resorptive processes and are characterized by different pathophysiological mechanisms. Drugs are available to treat bone metabolic pathologies, but they are either poorly effective or associated with undesired side effects that limit their use. The molecular mechanism underlying the most common metabolic bone disorders, and the availability, efficacy, and limitations of therapeutic options currently available are discussed here. A source for the unmet need of novel drugs to treat metabolic bone disorders is marine organisms, which produce natural osteoactive compounds of high pharmaceutical potential. In this review, we have inventoried the marine osteoactive compounds (MOCs) currently identified and spotted the groups of marine organisms with potential for MOC production. Finally, we briefly examine the availability of in vivo screening and validation tools for the study of MOCs.

Phosphate Metabolism and Pathophysiology in Parathyroid Disorders and Endocrine Tumors

The advent of new insights into phosphate metabolism must urge the endocrinologist to rethink the pathophysiology of widespread disorders, such as primary hyperparathyroidism, and also of rarer endocrine metabolic bone diseases, such as hypoparathyroidism and tumor-induced hypophosphatemia. These rare diseases of mineral metabolism have been and will be a precious source of new information about phosphate and other minerals in the coming years. The parathyroid glands, the kidneys, and the intestine are the main organs affecting phosphate levels in the blood and urine. Parathyroid disorders, renal tubule defects, or phosphatonin-producing tumors might be unveiled from alterations of such a simple and inexpensive mineral as serum phosphate. This review will present all these disorders from a ‘phosphate perspective’.

Changes in Bone Metabolism and Structure in Primary Hyperparathyroidism

Parathyroid hormone (PTH) is a key regulator of bone turnover. Depending on the duration of action, the hormone causes catabolic and anabolic effects by binding with specific receptors (PTHR1) in the bone. Various cells expressing PTHR1 on their surface are involved in the process – osteoblasts, osteocytes, bone marrow stromal cells, T-lymphocytes and macrophages. In physiological conditions PTH balances the bone metabolism. Intermittent pharmacological doses of PTH lead to the prevalence of bone formation and are used in the treatment of osteoporosis. Persistently elevated levels of PTH stimulate bone resorption by impacting mainly the cortical bone. New imaging and analysis techniques show that high PTH levels can also have an adverse effect on trabecular microarchitecture. Primary hyperparathyroidism (PHPT) is a disease characterized by increased bone metabolism, decreased bone mineral density (BMD), inadequate osteoid mineralization and an increased risk of fractures. Prolonged overproduction of PTH leads to stimulation of bone resorption and defects in bone formation, mainly causing loss of cortical bone mass, while in the trabecular bone predominate demineralization processes. One explanation of these findings is the enhanced stimulation of RANKL expression by osteoblasts with decreased OPG expression and bone formation at the same time.

Diagnosis and management of primary hyperparathyroidism--a scientific statement from the Department of Bone Metabolism, the Brazilian Society for Endocrinology and Metabolism

OBJECTIVE

To conduct a literature review on the diagnosis and management of primary hyperparathyroidism including the classical hipercalcemic form as well as the normocalcemic variant.

MATERIALS AND METHODS

This scientific statement was generated by a request from the Brazilian Medical Association (AMB) to the Brazilian Society for Endocrinology as part of its Clinical Practice Guidelines program. Articles were identified by searching in PubMed and Cochrane databases as well as abstracts presented at the Endocrine Society, Brazilian Society for Endocrinology Annual Meetings and the American Society for Bone and Mineral Research Annual Meeting during the last 5 years. Grading quality of evidence and strength of recommendation were adapted from the first report of the Oxford Centre for Evidence-based Medicine. All grades of recommendation, including "D", are based on scientific evidence. The differences between A, B, C and D, are due exclusively to the methods employed in generating evidence.

CONCLUSION

We present a scientific statement on primary hyperparathyroidism providing the level of evidence and the degree of recommendation regarding causes, clinical presentation as well as surgical and medical treatment.

Comparison of alendronate and raloxifene for the management of primary hyperparathyroidism

AIM

To evaluate and compare the efficacy of alendronate sodium (ALN) and raloxifene (RLX) for the management of primary hyperparathyroidism (PHPT) in postmenopausal female patients (pts) with osteoporosis.

METHODS

Twenty-four postmenopausal women with osteoporosis who were diagnosed with PHPT, but refused the option of surgery, were enrolled. Participants were sequentially randomized into two groups: an ALN-group of 12 pts (70 mg/week) and a RLX-group of 12 pts (60 mg/day). The control group consisted of 10 pts with PHPT who did not have any indications for surgery.

RESULTS

The decrease in ionized calcium levels was significantly more pronounced in the ALN group compared to the RLX and control groups (p<0.001). In terms of difference from baseline in bone mineral density (BMD) of the lumbar area in percentages over a period of 12 months, pts in the ALN and RLX groups both showed statistically significant improvements compared to pts in the control group (control vs ALN, p<0.001; control vs RLX, p<0.001). BMD measurements of the femoral and radial areas were comparable in all three groups.

CONCLUSIONS

ALN and RLX may improve bone density in the lumbar area of osteoporotic post-menopausal women with PHPT. The more significant decrease in serum calcium levels which was observed in the ALN group compared to both RLX and control groups, suggests that ALN could be used for the short-term control of calcium levels in patients awaiting surgery.

Cinacalcet for the treatment of primary hyperparathyroidism

The objective of this article is to review the literature regarding the treatment of primary hyperparathyroidism (PHPT) with a focus on cinacalcet. A MEDLINE (1965-June 2009) and bibliographic search of the English-language literature was conducted using the search terms cinacalcet, calcimimetics, primary hyperparathyroidism, and treatment. All articles identified in the search were included. Parathyroidectomy is curative for patients with PHPT; however, there are few options for patients who are not surgical candidates, who refuse surgery, or those with refractory PHPT after parathyroidectomy. Possible treatment options include estrogens, raloxifene, bisphosphonates, calcitonin, and cinacalcet. Cinacalcet has been shown to decrease serum calcium and parathyroid hormone serum levels in patients with PHPT. These trials, however, have not studied the effect of cinacalcet on patient-oriented outcomes such as bone mineral density, nephrolithiasis, or other complications of PHPT. Cinacalcet may be considered to reduce serum calcium and parathyroid hormone serum levels in patients with PHPT who cannot or will not undergo surgery and those with refractory PHPT after parathyroidectomy. Because the effects of cinacalcet on bone mineral density are uncertain, more frequent monitoring of bone mineral density may be required along with a medication proven to improve bone mineral density. Future studies should evaluate the effect of cinacalcet on complications of PHPT.

Calcium-lowering medications in patients with primary hyperparathyroidism: intraoperative findings and postoperative hypocalcemia

BACKGROUND

We analyzed how calcium-lowering medications (CLMs) influenced surgical findings in patients with primary hyperparathyroidism.

METHODS

A retrospective review was conducted of 281 patients undergoing surgery for primary hyperparathyroidism. Logistic regression evaluated the relationship between CLM and surgical findings. A mixed-effects model determined the influence of CLMs on these curves.

RESULTS

We found that CLM (P = .018) and a higher serum calcium level (P = .018) were variables making 4-gland hyperplasia less likely. Analysis of intraoperative parathyroid hormone (IOPTH) plots revealed that CLMs altered the kinetics (P = .043). However, the 2 groups did not differ in the number of measurements necessary for a 50% decrease in IOPTH levels. Multivariate logistic regression also revealed that patients taking more than one CLM had an increased association with postoperative hypocalcemia (P = .018).

CONCLUSIONS

Although CLM contributed to differences in IOPTH curves, their use does not require changing standard IOPTH protocol but should alert the surgeon to the risk of postoperative hypocalcemia.

Primary hyperparathyroidism in a young adult presenting with severe hypertension

Hypertension is a significant cause of morbidity and mortality in childhood. Endocrine-related hypertension is rare in children. Hypercalcmia due to hyperparathyroidism is a rare cause of endocrine-related hypertension in childhood. We present a patient with severe headache, who was diagnosed with hypertension due to hyperparathyroidism. Hyperparathyroidism should be kept in mind in children with hypertension accompanied by hypercalcemia and hypophosphatemia.

Primary hyperparathyroidism and the skeleton

Today, primary hyperparathyroidism (PHPT) in the developed countries is typically a disease with few or no obvious clinical symptoms. However, even in the asymptomatic cases the endogenous excess of PTH increases bone turnover leading to an insidious reversible loss of cortical and trabecular bone because of an expansion of the remodelling space and an irreversible loss of cortical bone due to increased endocortical resorption. In contrast trabecular bone structure and integrity to a large extent is maintained and there may be a slight periosteal expansion. Most studies have reported decreased bone mineral density (BMD) in PHPT mainly located at cortical sites, whereas sites rich in trabecular bone only show a modest reduction or even a slight increase in BMD. The frequent occurrence of vitamin D insufficiency and deficiency in PHPT and increased plasma FGF23 levels may also contribute to the decrease in BMD. The effect of smoking is unsolved. Epidemiological studies have shown that the relative risk of spine and nonspine fractures is increased in untreated PHPT starting up to 10 years before the diagnosis is made. Successful surgery for PHPT normalizes bone turnover, increases BMD and decreases fracture risk based on larger epidemiological studies. However, 10 years after surgery fracture risk appears to increase again due to an increase in forearm fractures. There are no randomized controlled studies (RCTs) demonstrating a protective effect of medical treatment on fracture risk in PHPT. Less conclusive studies suggest that vitamin D supplementation may have a beneficial effect on plasma PTH and BMD in vitamin D deficient PHPT patients. Hormone replacement therapy (HRT) and maybe SERM appear to reduce bone turnover and increase BMD. However, their nonskeletal side-effects preclude their use for this purpose. Bisphosphonates reduce bone turnover and increase BMD in PHPT as in osteoporosis and may be a therapeutical option in selected patients with low BMD. Obviously, there is a need for larger RCTs with fractures as end-points that appraise this possibility. Calcimimetics reduce plasma calcium and PTH in PHPT but has no beneficial effect on bone turnover or BMD. In symptomatic hypercalcaemic PHPT with low BMD where curative surgery is impossible or contraindicated a combination of a calcimimetic and a bisphosphonate may be an undocumented therapeutical option that needs further evaluation.