Direct and indirect assessment of the parathyroid hormone response to pamidronate therapy in Paget's disease of bone and hypercalcaemia of malignancy

[The clinical practice guidelines for primary hyperparathyroidism, short version]

Primary hyperparathyroidism (PHPT) is an endocrine disorder of parathyroid glands characterized by excessive secretion of parathyroid hormone (PTH) with an upper normal or elevated blood calcium level. Classical PHPT refers to a symptomatic, multi-system disorder, wich can lead to a significant decrease in the quality of life, disability of patients, and even an increased risk of premature death. Hypercalcemia and the catabolic effect of PTH on various cells are considered as the main pathogenetic mechanisms of the PHPT associated complications. In the last two decades, there has been an increase in the incidence of PHPT, mainly due to the mild forms of the disease, primarily due to the routine calcium screening in North America, Western Europe and, Asia. High prevalence of the disease, as well as the variety of clinical manifestations, cause the attention of different specialists - physicians, rheumatologists, urologists, nephrologists, cardiologists and other doctors. This review cover the main issues of Russian guidelines for the management of PHPT, approved in 2020, including laboratory and instrumental methods, differential diagnosis, surgical and conservative approach, short-term and long-term follow-up. This guidelines also include the recommendations for special groups of patients with hereditary forms of PHPT, parathyroid carcinoma, PHPT during pregnancy.

A case of severe, irreversible hypocalcemia after one dose of pamidronate administered for hypercalcemia of malignancy

This is a case report of a patient who developed severe, irreversible hypocalcemia after receiving one dose of pamidronate 90 mg for hypercalcemia of malignancy. Hypocalcemia is a known risk of bisphosphonate treatments, but the incidence of severe hypocalcemia is rare, and the risk factors are well established. However, in the treatment of hypercalcemia of malignancy, the treatment objective is to reduce the elevated serum calcium level, and the bisphosphonate is usually given as one time dose only. The potential for developing severe hypocalcemia may not be considered a significant concern in this setting compared to the setting of the treatment of bone metastasis, where the baseline serum calcium level is not elevated and the bisphosphonate is administered at a regular interval of every three to four weeks. Furthermore, there is unawareness of prevalence of vitamin D deficiency in cancer patients, especially in those with advanced cancer, which may lead to inadvertent, severe hypocalcemia from bisphosphonate treatment. The objective of this case report is to bring awareness to the risk of severe hypocalcemia in patients with hypercalcemia of malignancy and the high prevalence of unrecognized vitamin D deficiency in cancer patients.

Current recommendations for laboratory testing and use of bone turnover markers in management of osteoporosis

Osteoporosis is a major health problem worldwide, and is projected to increase exponentially due to the aging of the population. The absolute fracture risk in individual subjects is calculated by the use of algorithms which include bone mineral density (BMD), age, gender, history of prior fracture and other risk factors. This review describes the laboratory investigations into osteoporosis which include serum calcium, phosphate, creatinine, alkaline phosphatase and 25-hydroxyvitamin D and, additionally in men, testosterone. Parathyroid hormone (PTH) is measured in patients with abnormal serum calcium to determine its cause. Other laboratory investigations such as thyroid function testing, screening for multiple myeloma, and screening for Cushing's syndrome, are performed if indicated. Measurement of bone turnover markers (BTMs) is currently not included in algorithms for fracture risk calculations due to the lack of data. However, BTMs may be useful for monitoring osteoporosis treatment. Further studies of the reference BTMs serum carboxy terminal telopeptide of collagen type I (s-CTX) and serum procollagen type I N-terminal propeptide (s-PINP) in fracture risk prediction and in monitoring various treatments for osteoporosis may help expedite their inclusion in routine clinical practice.

Diagnosis of primary hyperparathyroidism: controversies, practical issues and the need for Australian guidelines

Primary hyperparathyroidism (PHPT) is one of the most common endocrine disease processes, however the clinical presentation in 2003 is typically characterized by minimal signs or symptoms of hypercalcaemia or para-thyroid hormone (PTH) excess. Recent developments in imaging and management of PHPT have been published, however the area of biochemical investigation has been relatively neglected. A group of experts convened in April 2002 to consider whether changes were needed to the 1990 consensus guidelines which defined criteria for the diagnosis and management of asymptomatic PHPT. It is appropriate to review the revised recommendations, which have been disseminated by the panel and were recently published. Each of the laboratory -analytes used to establish the diagnosis of PHPT and exclude alternative diagnoses or complications will be considered in succession in this review: (i) calcium, (ii) intact PTH, (iii) urinary calcium and (iv) 25 hydroxy-vitamin D. Furthermore, critical appraisal of the new diagnostic criteria and their applicability to Australian laboratories will be addressed. Finally, limitations and problems associated with the measurement of each analyte will be reviewed.

Prevention of appendicular bone loss in Paget's disease following treatment with intravenous pamidronate disodium

It has been shown previously that intravenous pamidronate treatment for severe Paget's disease is associated with appendicular bone loss. This 2 year study was designed to determine whether cotreatment with calcitriol and a calcium supplement would prevent this. Intravenous pamidronate was used to treat 49 patients with symptomatic Paget's disease. Patients were stratified into two groups of differing biochemical severity based on hydroxyproline excretion (HypE) expressed as micromoles per liter of glomerular filtrate (GF): (1) a severe group with HypE > 10 micromol/L GF; and (2) a moderate group with HypE 5-10 micromol/L GF. Within each group, patients were randomly allocated to receive supplements of calcium and calcitriol (supplemented) or no supplements (unsupplemented) after initiation of pamidronate therapy. The severe group received 360 mg of pamidronate as six doses of 60 mg once weekly and the moderate group received 240 mg as four weekly doses of 60 mg. Patients were followed for 24 months following treatment and had serial bone densitometry of the forearm measured as well as urine and plasma biochemistry. When the groups were combined, the unsupplemented patients showed a decrease in bone mineral density (BMD) at the ultradistal forearm site, which persisted to 24 months. Those supplemented with calcium and calcitriol showed an increase in BMD and the difference between the two groups was significant at all times posttreatment (p < 0.03). When the groups were analyzed separately, those with moderate disease again showed significant differences in BMD between supplemented and unsupplemented patients at all timepoints. In the severe group, the differences did not reach statistical significance due to smaller patient numbers. Similar changes in BMD were also observed at the forearm shaft site. When serial parathyroid hormone (PTH) levels (with the moderate and severe groups combined) were plotted against time since treatment the rise in PTH in the supplemented patients was less than the rise in the unsupplemented patients (p < 0.04). These results suggest that forearm bone loss after intravenous pamidronate treatment for moderate-to-severe Paget's disease can largely be prevented by administration of calcium and calcitriol. The mechanism may be a blunting of the secondary hyperparathyroidism that occurs after intravenous pamidronate. These findings may have wider application in moderate-to-severe Paget's disease treated with other bisphosphonates.

Effects of the antihypercalcemic drugs gallium nitrate and pamidronate on hormone release of pathologic human parathyroid cells

BACKGROUND

Gallium nitrate and the bisphosphonates pamidronate and its dimethylated derivative comprise antihypercalcemic drugs with actions on bone. This study examines the in vitro effects of these compounds on human parathyroid cells.

METHODS

Parathyroid hormone (PTH) release and the concentration of cytoplasmic calcium ion (Ca2+) of dispersed cells from parathyroid glands of 27 patients with sporadic primary or uremic hyperparathyroidism was measured.

RESULTS

In 1.25 mmol/L external Ca2+, 200 mumol/L gallium nitrate inhibited PTH release from preparations of primary and uremic hyperparathyroidism by 14% and 22%, respectively. Similar reductions were evident also in 0.5 and 3.0 mmol/L Ca2+. The gallium nitrate-induced suppression of PTH release was dose dependent in the 2 to 200 mumol/L range. Cytoplasmic Ca2+ concentration displayed a biphasic rise on elevation of external Ca2+ and remained unaffected by gallium nitrate. None of the bisphosphonates altered PTH release of pathologic human or normal bovine parathyroid cells.

CONCLUSIONS

The results support clinical usefulness of gallium nitrate through its dual actions on bone and the parathyroid. The findings substantiate that gallium may reduce PTH release by stabilization of the plasma membrane rather than by interference with the surface cation receptor mediating Ca2+ regulation of the secretion.

Survival in hypercalcaemic patients with cancer and co-existing primary hyperparathyroidism

Hypercalcaemia associated with malignancy is generally thought to carry a poor prognosis. Of 47 consecutive patients with hypercalcaemia and malignancy, serum parathyroid hormone (PTH) was elevated in seven, consistent with co-existing hyperparathyroidism. Median survival from onset of hypercalcaemia in these seven patients was 817 days; compared to 33 days in the remaining 40 patients with hypercalcaemia of malignancy, in whom PTH was suppressed (p = 0.007). Among patients with hypercalcaemia of malignancy, plasma PTH-related protein (PTHrP) concentration showed no correlation with survival (r2 = 2.1%), but one patient with increased levels of both PTH and PTHrP survived only nine days after the onset of hypercalcaemia. A raised PTH had a positive predictive value of 86% for survival > 100 days, and of 71% for survival > 1 year. A raised plasma PTHrP predicted death within 100 days with a positive predictive value of 69%. We conclude that measurement of serum PTH is indicated in patients with hypercalcaemia and malignancy to identify the 15% with hyperparathyroidism, since this is associated with prolonged survival. In patients with hyperparathyroidism, assay of plasma PTHrP may indicate concurrent hypercalcaemia of malignancy, with an associated poor prognosis.

Parathyroid hormone and parathyroid hormone-related protein in the investigation of hypercalcaemia in two hospital populations

BACKGROUND AND OBJECTIVE

Parathyroid hormone-related protein (PTHrP) produced by cancers has a central role as a humoral mediator of hypercalcaemia in patients with malignancy. Since the prevalences of hypercalcaemia of malignancy and parathyroid disease reflect the population studied, hypercalcaemic patients from a district general hospital (DGH) and an oncology centre (OC) were studied in order to assess the diagnostic role of assays for serum PTH and plasma PTHrP in different clinical settings.

DESIGN

A prospective study of consecutive patients presenting with their first episode of hypercalcaemia during an 18-month period.

PATIENTS

A total of 123 patients (DGH, n = 69; OC, n = 54) had corrected serum calcium concentrations > 2.65 mmol/l.

MEASUREMENTS

PTH, PTHrP, calcium and albumin were measured together with urine calcium and creatinine, enabling fractional calcium excretion to be assessed. Urine cyclic adenosine monophosphate was also measured.

RESULTS

Hypercalcaemia was attributed to malignancy alone in 72 patients (DGH, n = 20; OC, n = 52), benign causes in 42 (DGH, n = 42) and parathyroid disease coexisting with malignancy in 9 (DGH, n = 7; OC, n = 2). Plasma PTHrP levels were increased in 59/72 (82%) patients with hypercalcaemia due to malignancy. Measurements of both analytes contributed to a change in the final diagnosis in 12 patients (10%). Thus serum PTH was increased in seven patients with parathyroid disease coexisting with malignancy, and plasma PTHrP was increased in five patients with previous undiagnosed malignancy. Median survival for patients with parathyroid disease and coexisting malignancy was 13 months compared with 3 months for those with hypercalcaemia due to malignancy alone (P < 0.02).

CONCLUSIONS

Since hypercalcaemia was attributable to parathyroid disease in 10% of all patients with malignancy we advise measurement of serum PTH at the initial presentation of hypercalcaemia in all patients, while plasma PTHrP may be useful to identify those patients in whom malignancy may not be clinically apparent, or coexist with primary hyperparathyroidism.

Long-term elevation of 1,25-dihydroxyvitamin D after short-term intravenous administration of pamidronate (aminohydroxypropylidene bisphosphonate, APD) in Paget's disease of bone

We report the prolonged biochemical changes that occurred in patients with Paget's disease when treated for 2-10 days with pamidronate disodium (3-amino-1-hydroxypropylidine-1,1-bisphosphonate, APD), by i.v. administration and observed for 6 months following therapy. In all 24 patients studied, bone resorption (measured by urinary hydroxyproline/creatinine ratio, OHP/Cr) fell sharply on treatment, from 0.12 +/- 0.02 (mean +/- SEM; above reference limits) to 0.04 +/- 0.008 (reference range 0.006-0.027 for females, 0.005-0.020 for males), remaining at this level for 6 months after therapy. A fall in serum ionized calcium (Ca2+) to just below the reference limits with treatment (1.11 +/- 0.02 mM; reference range 1.14-1.18 mM), followed by a rapid return to normal levels (1.14 +/- 0.02 mM, mean +/- SEM) within 8 days of treatment, was presumably due to the cessation of release of calcium from bone. This was followed by secondary hyperparathyroidism and a rise in serum 1,25-dihydroxyvitamin D [1,25(OH)2D]. The hormonal responses, however, were profound. Serum immunoreactive PTH (iPTH) rose to twice pretreatment values (86 +/- 11 pM, mean +/- SEM; reference range for iPTH, > 50 years, < 50 pM; < 50 years, < 40 pM), returning to normal 4-8 weeks after therapy. Serum 1,25-(OH)2D levels rose to three times pretreatment values (300 +/- 20 pM, mean +/- SEM; reference range 50-150 pM), remaining above reference limits 4-8 weeks after therapy (188 +/- 15 pM, mean +/- SEM) and returning to normal values only after 12 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment of hypercalcaemia with pamidronate in patients with end stage renal failure

Pamidronate was given to 10 patients with end stage renal failure who had become symptomatically hypercalcaemic due to the use of calcium based phosphate binders and alphacalcidol. All patients were initially treated with rehydration, increased dialysis and withdrawal of drugs, however despite this they remained symptomatic and the serum calcium remained elevated, mean 3.89 mmol/l (range 3.44-4.74). Pamidronate was given, and the serum calcium had declined to 2.92 mmol/l (2.79-3.84), p < 0.01 by the third day. The reduction in serum calcium observed with pamidronate was more rapid than that in 9 patients who developed asymptomatic hypercalcaemia, mean serum calcium 3.45 mmol/l (3.4-3.56), with an actual median reduction of 0.72 mmol/l (0.37-1.30) in the pamidronate group after 3 days compared to 0.20 mmol/l (0.10-0.52) in the conservatively treated asymptomatic group, p < 0.01, and a median percentage decrease of 19% (10-30) in the pamidronate group and 6% (3-15) in the asymptomatic group, p < 0.01. In this study pamidronate was a safe and effective agent in reducing serum calcium in a group of hypercalcaemic dialysis patients.

Coincidental occurrence of primary hyperparathyroidism and cancer-associated hypercalcaemia in a middle-aged man

Primary hyperparathyroidism (PHPT) is found not uncommonly in patients with cancer. In this report, however, we describe a patient where both humoral hypercalcaemia of malignancy and PHPT were present coincidentally. A 47-year-old man was found to have PHPT due to parathyroid hyperplasia. Serum parathyroid hormone (PTH) levels, which were elevated before parathyroidectomy, were undetectable post-operatively; however, hypercalcaemia persisted. Nephrogenous cyclic adenosine monophosphate was elevated along with this undetectable PTH, indicative of the presence of a PTH-like factor in the serum. This was confirmed by the finding of an elevated level of PTH-related protein (PTHrP) in plasma (9.1 pmol/l, normal < 2.6 pmol/l). Secondary carcinoma was identified in a lesion in the region of the manubrium sternii. This stained positively for PTHrP by immunocytochemistry and PTHrP messenger RNA was detected by in-situ hybridization. This case illustrates the value of sensitive PTH assays in distinguishing PHPT from other causes of hypercalcaemia and also shows the importance of considering primary hyperparathyroidism in the differential diagnosis of the patient with cancer and hypercalcaemia.