Aminopropylidine diphosphonate (APD) in mild primary hyperparathyroidism: effect on clinical status

Efficacy and Safety of Intravenous Pamidronate for Parathyroid Hormone-dependent Hypercalcemia in Hospitalized Patients

CONTEXT

Bisphosphonates are effective for hypercalcemia of malignancy (HOM). Efficacy and safety data for bisphosphonates in parathyroid hormone-related hypercalcemia (PTHRH) are rare, including pamidronate (Pam), which is not indicated for this condition.

OBJECTIVE

This work aims to evaluate the efficacy and safety of Pam for moderate-to-severe PTHRH.

METHODS

This retrospective case-control study was conducted at a tertiary care medical center. Patients included adults hospitalized with serum calcium levels greater than 12 mg/dL, from October 29, 2013 to December 17, 2019. Etiology was categorized as PTHRH or PTH-independent. Clinical and laboratory data of PTHRH patients treated with Pam (PTHRH-Pam+) were compared to Pam-untreated counterparts (PTHRH-Pam-).

RESULTS

Thirty-four patients with 37 hospitalizations for PTHRH (Pam-treated and -untreated) met the inclusion criteria. Pam was given in 24 of 37 cases (64.8%). Admission serum calcium levels for the PTHRH-Pam+ group were higher than for PTHRH-Pam- group (14.4 mg/dL vs 13.0 mg/dL, P = .005). Median total Pam dose was 60 mg (range, 30-180 mg) in the treated group. Serum calcium decreased 3.5 mg/dL for PTHRH-Pam+ vs 1.6 mg/dL for PTHRH-Pam- (P = .003). No PTHRH-Pam+ patients developed hypocalcemia or acute kidney injury. Nadir serum phosphorus levels were lower in the PTHRH-Pam+ vs PTHRH-Pam- group (1.7 mg/dL vs 2.4 mg/dL, respectively, P = .004). Three PTHRH-Pam+ patients developed severe hypophosphatemia; all resolved with intravenous and oral supplementation. Seventeen patients underwent parathyroidectomy, of whom 10 received Pam within 28 days preoperatively. Postoperatively, 4 developed hypocalcemia and 3 hypophosphatemia.

CONCLUSION

This study demonstrates that Pam is effective and safe for treating PTHRH, while ensuring close laboratory monitoring of calcium and phosphorus metabolism. Larger, prospective studies are needed to establish the role of Pam and other potent bisphosphonates in moderate-to-severe PTHRH.

Contemporary Medical Management of Primary Hyperparathyroidism: A Systematic Review

INTRODUCTION

Primary hyperparathyroidism is increasingly an asymptomatic disease at diagnosis, but the recognized guidelines for management are based on evidence obtained from studies on patients with symptomatic disease, and surgery is not always indicated. Other patients are unable to undergo surgery, and thus a medical treatment is warranted. This systematic review provides an overview of the existing literature on contemporary pharmaceutical options available for the medical management of primary hyperparathyroidism.

METHODS

Databases of medical literature were searched for articles including terms for primary hyperparathyroidism and each of the included drugs. Data on s-calcium, s-parathyroid hormone, bone turnover markers, bone mineral density (BMD) and hard endpoints were extracted and tabulated, and level of evidence was determined. Changes in s-calcium were estimated and a meta-regression analysis was performed.

RESULTS

The 1,999 articles were screened for eligibility and 54 were included in the review. Weighted mean changes calculated for each drug in s-total calcium (mean change from baseline ± SEM) were pamidronate (0.31 ± 0.034 mmol/l); alendronate (0.07 ± 0.05 mmol/l); clodronate (0.20 ± 0.040 mmol/l); mixed bisphosphonates (0.16 ± 0.049 mmol/l); and cinacalcet (0.37 ± 0.013 mmol/l). The meta-analysis revealed a significant decrease of effect on s-calcium with time for the bisphosphonates (Coef. -0.049 ± 0.023, p = 0.035), while cinacalcet proved to maintain its effect on s-calcium over time. Bisphosphonates improved BMD while cinacalcet had no effect.

DISCUSSION

The included studies demonstrate advantages and drawbacks of the available pharmaceutical options that can prove helpful in the clinical setting. The great variation in how primary hyperparathyroidism is manifested requires that management should rely on an individual evaluation when counseling patients. Combining resorptive agents with calcimimetics could prove rewarding, but more studies are warranted.

Primary hyperparathyroidism: review and recommendations on evaluation, diagnosis, and management. A Canadian and international consensus

The purpose of this review is to assess the most recent evidence in the management of primary hyperparathyroidism (PHPT) and provide updated recommendations for its evaluation, diagnosis and treatment. A Medline search of "Hyperparathyroidism. Primary" was conducted and the literature with the highest levels of evidence were reviewed and used to formulate recommendations. PHPT is a common endocrine disorder usually discovered by routine biochemical screening. PHPT is defined as hypercalcemia with increased or inappropriately normal plasma parathyroid hormone (PTH). It is most commonly seen after the age of 50 years, with women predominating by three to fourfold. In countries with routine multichannel screening, PHPT is identified earlier and may be asymptomatic. Where biochemical testing is not routine, PHPT is more likely to present with skeletal complications, or nephrolithiasis. Parathyroidectomy (PTx) is indicated for those with symptomatic disease. For asymptomatic patients, recent guidelines have recommended criteria for surgery, however PTx can also be considered in those who do not meet criteria, and prefer surgery. Non-surgical therapies are available when surgery is not appropriate. This review presents the current state of the art in the diagnosis and management of PHPT and updates the Canadian Position paper on PHPT. An overview of the impact of PHPT on the skeleton and other target organs is presented with international consensus. Differences in the international presentation of this condition are also summarized.

Medical management of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is the most common cause of hypercalcemia in the outpatient population. It is diagnosed in most individuals in the Western world at an asymptomatic stage without signs or symptoms of parathyroid hormone (PTH) calcium excess. Nonspecific symptoms include weakness, malaise, fatigue, and possible mood disturbances, which may be present at the time of diagnosis. The diagnosis of PHPT is confirmed in the presence of hypercalcemia and a normal or elevated PTH level in the absence of conditions that mimic PHPT. Indications for surgery have recently been revised based on international consensus, and surgery is advised in the presence of significant hypercalcemia, impaired renal function, and osteoporosis and in individuals younger than 50yr. The classical complications of PHPT are skeletal fragility, nephrolithiasis, and nephrocalcinosis. Surgery is always appropriate in an individual with confirmed PHPT after excluding conditions that can mimic PHPT and in the absence of contraindications. Individuals with asymptomatic PHPT not meeting the guidelines for surgery or those with contraindications for surgery may be followed and considered for medical management. For those at an increased risk of fragility fracture, antiresorptive therapy may be considered with close monitoring of biochemical data and bone densitometry. Targeted therapy with a calcimimetic agent may be of value in lowering serum calcium and PTH. There are currently no fracture data for the medical options available, and prospective randomized controlled trials are required to confirm the effects of medical therapy on fracture risk reduction in those with asymptomatic PHPT.

Parathyromatosis: a rare yet problematic etiology of recurrent and persistent hyperparathyroidism

Recurrent or persistent hyperparathyroidism is an uncommon yet challenging clinical problem, and parathyromatosis is one of its very rare causes. In this minireview, we review causes of recurrent hyperparathyroidism and all cases of parathyromatosis available in the literature. The clinical course of a case of parathyromatosis with the longest follow-up (1977-2011) is described. Similar cases reported between 1975 and the present are reviewed and analyzed to characterize the clinical presentation, course, and management of this rare condition. Parathyromatosis, which is benign parathyroid tissue seeding, has been detailed in 35 patients in the English literature. The majority were female subjects, with end-stage renal disease, in their fifth to sixth decade of life. In most cases, the diagnosis was made intraoperatively; and the condition was often refractory to surgery. A calcimimetic agent was used in 5 cases with end-stage renal disease; serum calcium and/or parathyroid hormone levels decreased in 4 subjects, but only one was reported to experience increments in bone density. Medical management combining a calcimimetic with a bisphosphonate may therefore be a preferred alternative.

Medical management of asymptomatic primary hyperparathyroidism: proceedings of the third international workshop

BACKGROUND

Primary hyperparathyroidism (PHPT) is a common endocrine disorder that is frequently asymptomatic. The 2002 International Workshop on Asymptomatic PHPT addressed medical management of asymptomatic PHPT and summarized the data on nonsurgical approaches to this disease. At the Third International Workshop on Asymptomatic PHPT held in May 2008, this subject was reviewed again in light of data that have since become available. We present the results of a literature review of advances in the medical management of PHPT.

METHODS

A series of questions was developed by the International Task Force on PHPT. A comprehensive literature search for relevant studies evaluating the management of PHPT with bisphosphonates, hormone replacement therapy, raloxifene, and calcimimetics was conducted. Existing guidelines and recent unpublished data were also reviewed. All selected relevant articles were reviewed, and the questions developed by the International Task Force were addressed by the Consensus Panel.

RESULTS

Bisphosphonates and hormone replacement therapy are effective in decreasing bone turnover in patients with PHPT and improving bone mineral density (BMD). Fracture data are not available with either treatment. Raloxifene also lowers bone turnover in patients with PHPT. None of these agents, however, significantly lowers serum calcium or PTH levels. The calcimimetic cinacalcet reduces both serum calcium and PTH levels and raises serum phosphorus. Cinacalcet does not, however, reduce bone turnover or improve BMD.

CONCLUSIONS

Bisphosphonates and hormone replacement therapy provide skeletal protection in patients with PHPT. Limited data are available regarding skeletal protection in patients with PHPT treated with raloxifene. Calcimimetics favorably alter serum calcium and PTH in PHPT but do not significantly affect either bone turnover or BMD. Medical management of asymptomatic PHPT is a promising option for those who are not candidates for parathyroidectomy.

Elimination and clearance of pamidronate by haemodialysis (Brief Communication)

Pamidronate (APD), a third-generation bisphosphonate, has proven to be useful in haemodialysis (HD) patients with ectopic calcifications and hypercalcaemia. Little is known about bisphosphonates clearance in patients undergoing HD. The authors' main objective was to study HD removal and clearance of APD. In total, 23 HD-requiring anuric end-stage renal disease (ESRD) adult individuals (12 men) aged 61.7 +/- 13 (mean +/- SD) years were admitted into the study. APD clearance and elimination were evaluated by (99m)Technetium APD (half-life 6 h). In total, 1 mg of labelled APD was injected via the arteriovenous graft prior to the start of HD. Blood samples were then drawn from the arterial (predialyser) and venous (postdialyser) lines of the extracorporeal circuit 2 h after the HD onset. In a subgroup of patients (n: 15) the dialysate was collected and quantified during the three initial HD hours. Venous APD concentrations (postdialyser) were 72 + 7% of arterial (predialyser) concentrations. Mean APD clearance was 69.3 + 16.6 mL/min, and mean APD extraction during dialysis session was 31.6 + 10.1%. In the present study involving HD-requiring anuric ESRD patients APD was successfully eliminated by HD. At the dose administered here none of the participants reported adverse events. APD is a potentially useful drug to be administered to HD-requiring ESRD patients, the understanding of its removal during HD as well as its dialytic clearance allows for a safer management of a drug that is usually eliminated by renal excretion.

Usefulness of pamidronate in severe secondary hyperparathyroidism in patients undergoing hemodialysis

BACKGROUND

Although bisphosphonates have been widely used to treat bone diseases characterized by increased bone resorption, there are limited data showing their possible usefulness in patients on hemodialysis (HD) with secondary hyperparathyroidism.

METHODS

The aim of this study was to evaluate the efficacy and safety of pamidronate in HD patients affected by severe secondary hyperparathyroidism and moderate hypercalcemia who were receiving intravenous calcitriol (Calcijex).

RESULTS

In this prospective one-year, open-labeled study, 13 patients (9 women/4 men) with a mean age of 64 +/- 9 years and a mean time on dialysis of 94 +/- 61 months were evaluated. The inclusion criteria were: iPTH>500 pg/mL, Ca>11 mg/dL, P <6 mg/dL, and osteopenia (T-score <-1 SD). Blood levels of Ca, P, alkaline phosphatase (AP), and iPTH were assessed at the beginning of the study and every month. Radiographs of the vertebral spine and bone mineral density (BMD) (lumbar spine and femoral neck) were assessed basal and every 6 months. All patients received 60 mg of pamidronate intravenously every two months throughout the study period. Calcitriol and phosphate binders were adjusted according to iPTH, Ca, and P blood levels. BMD increased in both the lumbar and femoral neck scans (mean increase of 33%) at 6 and 12 months. iPTH increased at 3 months in all patients, and decreased more than 50% in 10 patients after increasing the calcitriol doses. Three patients had no response. A slight decrease in Ca and P was observed in all patients with no significant changes in AP. There were no adverse events.

CONCLUSION

Pamidronate is effective in controlling hypercalcemia in patients on HD with secondary hyperparathyroidism and allows for a more aggressive use of intravenous calcitriol.

Alendronate in the treatment of primary hyperparathyroid-related osteoporosis: a 2-year study

We investigated the effect of alendronate on calcium, PTH, and bone mineral density in 27 female and 5 male patients with primary hyperparathyroidism. The treatment group [n = 14; T score < or = -2.5 SD at the femoral neck (FN) or T < or = -1.0 SD plus previous nonvertebral fracture] was given alendronate 10 mg/d for 24 months. The second group (n = 18; T score > -2.5 SD at the FN) was untreated. Biochemistry was repeated at 1.5, 3, 6, 12, 18, and 24 months, and dual-energy x-ray absorptiometry at 12 and 24 months. There were no significant between-group baseline differences in calcium, creatinine, or PTH. Alendronate-treated patients gained bone at all sites [lumbar spine (LS), 1 yr gain, +7.3 +/- 1.7%; P < 0.001; 2 yr, +7.3 +/- 3.1%; P = 0.04). Untreated patients gained bone at the LS over 2 yr (+4.0 +/- 1.8%; P = 0.03) but lost bone elsewhere. Calcium fell nonsignificantly in the alendronate group between baseline (2.84 +/- 0.12 mmol/liter) and 6 wk (2.76 +/- 0.09 mmol/liter), with a nonsignificant rise in PTH (baseline, 103.5 +/- 14.6 ng/liter; 6 wk, 116.7 +/- 15.6 ng/liter). By 3 months, values had reverted to baseline. In primary hyperparathyroidism, alendronate is well tolerated and significantly improves bone mineral density at the LS (with lesser gains at FN and radius), especially within the first year of treatment. Short-term changes in calcium and PTH resolve by 3 months.

Effects of oral alendronate in elderly patients with osteoporosis and mild primary hyperparathyroidism

In a large proportion of the patients with primary hyperparathyroidism (PHPT), a variable degree of osteopenia is the only relevant manifestation of the disease. Low bone mineral density (BMD) in patients with PHPT is an indication for surgical intervention because successful parathyroidectomy results in a dramatic increase in BMD. However, low BMD values are almost an invariable finding in elderly women with PHPT, who are often either unwilling or considered unfit for surgery. Bisphosphonates are capable of suppressing parathyroid hormone (PTH)-mediated bone resorption and are useful for the prevention and treatment of postmenopausal osteoporosis. In this pilot-controlled study, we investigated the effects of oral treatment with alendronate on BMD and biochemical markers of calcium and bone metabolism in elderly women presenting osteoporosis and mild PHPT. Twenty-six elderly patients aged 67-81 years were randomized for treatment with either oral 10 mg alendronate on alternate-day treatment or no treatment for 2 years. In the control untreated patients a slight significant decrease was observed for total body and femoral neck BMD, without significant changes in biochemical markers of calcium and bone metabolism during the 2 years of observation. Urine deoxypyridinoline (Dpyr) excretion significantly fell within the first month of treatment with alendronate, while serum markers of bone formation alkaline phosphatase and osteocalcin fell more gradually and the decrease became significant only after 3 months of treatment; thereafter all bone turnover markers remained consistently suppressed during alendronate treatment. After 2 years in this group we observed statistically significant increases in BMD at lumbar spine, total hip, and total body (+8.6 +/- 3.0%, +4.8 +/- 3.9%, and +1.2 +/- 1.4% changes vs. baseline mean +/- SD) versus both baseline and control patients. Serum calcium, serum phosphate, and urinary calcium excretion significantly decreased during the first 3-6 months but rose back to the baseline values afterward. Increase in serum PTH level was statistically significant during the first year of treatment. These preliminary results may make alendronate a candidate as a supportive therapy in patients with mild PHPT who are unwilling or are unsuitable for surgery, and for whom osteoporosis is a reason of concern.

Medical approaches to primary hyperparathyroidism

Medical therapy is useful in cases of acute primary hyperparathyroidism, patients with recurrent disease, and parathyroid carcinoma. Among the therapeutic agents that have been employed, oral phosphate, bisphosphonates, and estrogens have been successful. The newly described calcimimetic agents directly block secretion of parathyroid hormone from the glands and offer an important new approach to medical therapy of primary hyperparathyroidism.

Short-term inhibition of parathyroid hormone secretion by a calcium-receptor agonist in patients with primary hyperparathyroidism

BACKGROUND

Surgery is the usual therapy for patients with primary hyperparathyroidism. We investigated the ability of a calcimimetic drug that inhibits parathyroid hormone secretion in vitro to decrease serum parathyroid hormone and calcium concentrations in patients with this disorder.

METHODS

We performed a randomized, placebo-controlled study of single oral doses of 4 to 160 mg of the calcium-receptor agonist drug R-568 in 20 postmenopausal women with mild primary hyperparathyroidism. At base line, the mean (+/-SE) serum calcium concentration was 10.7+/-0.2 mg per deciliter (2.67+/-0.05 mmol per liter). Serum parathyroid hormone and calcium were measured repeatedly after each dose, and safety was assessed.

RESULTS

Administration of R-568 resulted in a dose-dependent inhibition of parathyroid hormone secretion. The mean serum parathyroid hormone concentration, which was 77+/-11 pg per milliliter (18.8+/-2.7 pmol per liter; normal range, 16 to 65 pg per milliliter [3.9 to 15.9 pmol per liter) at base line, fell by 26+/-8 percent after 20 mg of R-568 (P=0.03), by 42+/-7 percent after 80 mg (P = 0.01), and by 51+/-5 percent after 160 mg (P=0.005). Serum ionized calcium concentrations fell only after the 160-mg dose, with the decrease closely following the decrease in the serum parathyroid hormone concentration.

CONCLUSIONS

The calcimimetic drug R-568 reduces serum parathyroid hormone and ionized calcium concentrations in postmenopausal women with primary hyperparathyroidism.

The skeletal effects of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a common endocrine disorder which occurs most frequently in post-menopausal women and is characterized by mild, stable, and often asymptomatic hypercalcaemia. Chronic parathyroid hormone excess stimulates bone remodelling by inducing production by osteoblasts of soluble factors which stimulate both bone formation and osteoclastic bone resorption. Studies of bone mineral density (BMD) in PHPT suggest that bone loss is accelerated, leading to osteopenia, particularly at sites of cortical bone. Studies of fracture incidence in PHPT have produced conflicting results. Interventional studies have demonstrated that both parathyroid adenomectomy and estrogen replacement therapy increase BMD in patients with PHPT. Patients with PHPT should undergo BMD measurement, and receive treatment designed to stabilize bone mass if there is evidence of either osteopenia or accelerated bone loss.

Cyclical etidronate and calcium carbonate (with citrate) supplementation for osteoporosis unmasking primary hyperparathyroidism

An 88 year old lady undergoing cyclical etidronate and calcium carbonate (with citrate) therapy for vertebral osteoporosis was found to be symptomatically hypercalcaemic at the end of the first cycle of treatment. She had been previously asymptomatic and normocalcaemic, but was subsequently found to have primary hyperparathyroidism. This condition is most prevalent in postmenopausal females--the same patient group at risk of osteoporosis. Serum calcium should be measured after commencing cyclical etidronate and calcium carbonate. If hypercalcaemia is detected primary hyperparathyroidism should be excluded as an underlying, cause.

Primary hyperparathyroidism

Primary hyperparathyroidism is not rare. It is particularly common after the age of 50 and may affect up to 3% of postmenopausal women. It is commonly found as a result of blood tests performed for other reasons and is therefore often asymptomatic. Surgical treatment is recommended for patients with renal stone disease, plasma calcium above 3 mmol/L and accelerated bone loss (e.g., bone density < 3 standard deviations below the young normal mean). There is considerable debate about whether mild asymptomatic disease should be treated, but if there is rapid bone loss, either surgical or medical therapy with hormones or bisphosphonates is indicated.

Prolonged remission of hypercalcaemia due to parathyroid carcinoma with pamidronate

Parathyroid carcinoma is rare and the associated hypercalcaemia is often resistant to all treatment. A case is described in which prolonged control of hypercalcaemia has been achieved by infrequent infusions of pamidronate despite continuing hypersecretion of parathyroid hormone.

Decrease of serum calcium concentration and lost influence of calcium on parathyroid hormone release in a patient with primary hyperparathyroidism after treatment with diphosphonates

Prolonged decrease of elevated serum calcium levels after treatment with diphosphonates in patients with primary hyperparathyroidism (pHPT) is very rare. A patient with water clear cell hyperplasia and five enlarged glands is presented who received diphosphonates (day 1 through day 8 dichloromethylene diphosphonate orally and a single dose of 60 mg pamidronate on day 8 intravenously) leading to a significant fall in serum calcium levels. Surprisingly, there was no reactive increase in intact parathyroid hormone (PTH) in the following 18 days. Patients with missing PTH regulation to hypocalcemia after diphosphonates who need a period of stabilization prior to parathyroid surgery might benefit most from this therapy.

Parenteral pamidronate prevents thyroid hormone-induced bone loss in rats

Pamidronate (APD) is a bisphosphonate that prevents bone loss from a variety of causes. We studied the role of APD in preventing thyroid hormone-induced bone loss. A total of 32 rats were assigned to one of four treatment groups: (1) -APD/triiodothyronine (-T3), (2) -APD/+T3, (3) +APD/-T3, or (4) +APD/+T3. In the first of two studies, the rats received APD for the first week and T3 for the second week, and then their blood was analyzed for alkaline phosphatase and osteocalcin. Alkaline phosphatase and osteocalcin were significantly higher (p < 0.05) in hyperthyroid rats (-APD/+T3, 3.9 +/- 0.25 mukat/liter and 23 +/- 1.6 nM, respectively) than in control animals (2.53 +/- 0.28 mukat/liter and 18.3 +/- 1.4 nM, respectively). Hyperthyroid rats pretreated with APD (+APD/+T3) had levels of alkaline phosphatase and osteocalcin no different from controls. In a second study, rats were divided into the same four groups, except they received APD/placebo and T3/placebo concomitantly for 3 weeks. At the end of the study, bone mineral density (BMD) of the femur, spine, and whole body was measured by dual-energy x-ray absorptiometry, and the calcium content of the femora was measured directly. In hyperthyroid rats (-APD/+T3) BMD was significantly lower than in controls in the spine (0.201 +/- 0.004 versus 0.214 +/- 0.002 g/cm2, p < 0.05) and femur (0.204 +/- 0.003 versus 0.218 +/- 0.002, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of Severe Hypercalcemia in Primary Hyperparathyroidism with Aminopropylidene Diphosphonate

Objective:

To test the clinical usefulness and potency for decreasing plasma calcium concentration of an intravenously administered diphosphonate (aminopropylide diphosphonate [APD]) in a patient with hypercalcemic crisis secondary to primary hyperparathyroidism, unresponsive to hydration and furosemide, and who was ineligible for surgery because of cardiac conduction defects.

Design:

Case report.

Setting:

Referred care setting.

Intervention:

The patient received APD 15 mg/d, dissolved in 100 mL of isotonic NaCl 0.9% and infused in one hour.

Main Outcome Measure:

Plasma calcium concentration.

Results:

The patient's plasma calcium concentration fell considerably in a few days. The concomitant decrease in urinary calcium excretion indicates that this fall is caused by a decreased entry of calcium to the extracellular fluid and not to increased renal calcium excretion. After nine days, a parathyroid adenoma was removed; plasma calcium concentration remained normal during the following three years.

Conclusions:

APD is a useful adjunct to medical therapy in patients with hypercalcemic crisis secondary to primary hyperparathyroidism.

Medical management of asymptomatic primary hyperparathyroidism

Patients with mild asymptomatic primary hyperparathyroidism who do not meet currently accepted guidelines for surgery may be followed medically. General medical management of these individuals should be directed toward maintaining adequate hydration, therapy of hypertension, and avoiding immobilization. Diuretics should be used only with caution. Moderate dietary calcium intake (500-800 mg/day) should be encouraged. Propranolol and cimetidine are not useful in the therapy of primary hyperparathyroidism. Oral phosphate is efficacious in lowering serum and urinary calcium. However, because of concerns related to ectopic calcification, phosphate is usually reserved for those patients who meet surgical guidelines but who are not to undergo surgery. Bisphosphonates, potent inhibitors of osteoclast-mediated bone resorption, have been shown to lower serum and urinary calcium in patients with primary hyperparathyroidism. However, long-term data on their efficacy in this disorder are not yet available. The use of bisphosphonates at the present time is generally restricted to the research setting. More potent bisphosphonates as well as the design of newer agents that interfere with parathyroid hormone secretion may become very useful in future approaches to the medical management of primary hyperparathyroidism.