Treatment of hypokalemia with amiloride unmasked hypercalcemia and hyperparathyroidism: A case report

Colonic pseudo-obstruction, also called Ogilvie's syndrome, occurs due to impaired intestinal propulsion, and may be caused by electrolyte imbalances such as hypokalemia and some endocrine disorders such as hyperparathyroidism. Secretory diarrhea due to intestinal pseudo-obstruction can cause hypokalemia. Diuretics such as amiloride can be used to treat hypokalemia, however in this case, treatment with amiloride induced hypercalcemia and unmasked hyperparathyroidism. A 73-year-old female with a history of hypertension and parathyroid adenoma presented with recurrent colonic pseudo-obstruction and chronic hypokalemia. Her hypokalemia was treated with amiloride, causing hypercalcemia of 14.4 mg/dL, elevated PTH, and altered mental status. Amiloride was subsequently discontinued with improvement in her symptoms, and her hyperparathyroidism was treated with cinacalcet. To our knowledge, this is the first report of amiloride unmasking hyperparathyroidism and inducing hypercalcemia.

The association between proton pump inhibitors and hyperparathyroidism: a potential mechanism for increased fracture-results of a large observational cohort study

Proton pump inhibitors (PPIs) are associated with increased risk of osteoporotic fracture; however, the mechanism is unclear. PPI users taking calcium supplements were more likely to have hyperparathyroidism compared to non-users (OR 1.56, CI 1.08-2.23, p = 0.018). This highlights the importance of monitoring PPI use, especially in older adults.

PURPOSE

Proton pump inhibitors (PPIs) are associated with increased risk of osteoporotic fracture. Hyperparathyroidism may be implicated, but few studies have considered this relationship. This study evaluated the relationship between PPI use and hyperparathyroidism in older adults.

METHODS

Participants were from the TUDA study, a large cross-sectional cohort of older Irish adults. Participants with an estimated glomerular filtration rate (eGFR) < 30 ml/min and serum calcium > 2.5 mmol/l were excluded to avoid hyperparathyroidism due to chronic renal disease and primary hyperparathyroidism. Hyperparathyroidism was defined as a parathyroid hormone (PTH) > 65 pg/ml. Multivariate regression models were used to analyse the relationship between PPI use and hyperparathyroidism.

RESULTS

A total of 4139 participants met the inclusion criteria, of whom 37.8% (n = 1563) were taking PPI medication. PPI use was identified in 41.4% of calcium supplement users and 35.4% of non-calcium supplement users. Overall, compared to non-users of PPIs, those taking PPIs were older (74.8 vs 72.9 years, p < 0.001) and had a higher prevalence of hyperparathyroidism (17.8 vs 11.0%, p < 0.001). In those taking calcium supplements (but not in non-users), PPI use was significantly associated with hyperparathyroidism (OR 1.56, CI 1.08-2.23, p = 0.018) after adjusting for age, sex, body mass index, serum vitamin D, eGFR, timed-up-and-go, dairy intake, medications, and comorbidities.

DISCUSSION

The results are consistent with the hypothesis of PPIs reducing calcium absorption, leading to a rise in PTH which could mediate increased fracture risk. No relationship of PPI use with hyperparathyroidism was observed in non-users of calcium supplements, possibly owing to lower dietary calcium intake. These results highlight the importance of monitoring PPI use, especially in older adults at risk of fracture.

Surgery for Renal Hyperparathyroidism in the Era of Cinacalcet: A Single-Center Experience

BACKGROUND AND AIMS

There are only few data on the influence of cinacalcet on the outcome of parathyroidectomy in patients with renal hyperparathyroidism. Indication and timing of surgery have changed since its introduction, especially with regard to kidney transplantation. Therefore, we retrospectively analyzed patients undergoing parathyroidectomy for renal hyperparathyroidism in our institution.

MATERIAL AND METHODS

Between 2008 and 2015, 196 consecutive operations in 191 patients were analyzed. About 80 operations (41%) were performed in patients receiving cinacalcet compared with 116 operations (59%) in patients without cinacalcet. Clinical data, preoperative medication, pre- and postoperative laboratory values, type and details of surgery including complications, as well as cardiovascular complications and kidney transplantation with graft function were recorded.

RESULTS

Demographical data were similar in patients with or without cinacalcet treatment. A total of 54% of patients received a kidney graft before or after parathyroidectomy. Pre- and postoperative parathormone levels were similar in both groups (preoperatively 755 vs 742 ng/L, postoperatively 50 vs 46 ng/L, p > 0.10), whereas patients with cinacalcet showed significantly lower calcium levels preoperatively (2.28 vs 2.41 mmol/L, p = 0.0002). There was no difference in recurrence or persistence of hyperparathyroidism, duration of surgery, hospital stay, or complication rate. Creatinine levels in patients with tertiary hyperparathyroidism were similar after 1-year follow-up.

CONCLUSION

Cinacalcet did not influence outcome of patients with parathyroidectomy for renal hyperparathyroidism and can be safely offered to patients not responding to medical treatment.

Recent advances in treatment of haemodialysis

Haemodialysis remains the most widely used treatment for patients with end-stage renal disease. Despite the progress that has occurred in the treatment of end-stage renal disease over the last six decades, there has been a failure to translate this into the desired clinical benefits, with morbidity and mortality rates among patients on haemodialysis remaining unacceptably high. Recently, however, there have been expectations that the significant advances that took place over the last few years may result in improved outcomes. New medications for the treatment of anaemia and secondary hyperparathyroidism, as well as novel trends in the areas of iron therapy, diabetes management and physical exercise are among the most important advances which, taken together, are changing the standards of care for patients on haemodialysis. The latest advances, of relevance not only to specialists in Renal Medicine but also to general practitioners caring for these patients, are reviewed in this collaborative paper.

Cinacalcet use in pediatric chronic kidney disease. A survey study

OBJECTIVES

To evaluate the practice and attitude of pediatrics nephrologists about cinacalcet use in children.

METHODS

An electronic structured questionnaire was answered by pediatric nephrologists practicing in the Kingdom of Saudi Arabia (KSA) and Gulf Council countries (GCC).

RESULTS

A total of 42  pediatric nephrologists responded, of them, 42% used cinacalcet for young children ≤5 years of age and 79% used for children. There were wide variations in the method of administration (examples: crushed, divided, whole tablets), monitoring, doses and response definition, and follow-up. No serious complications after starting cinacalcet was observed in 50%, while 40% reported various complications, mainly hypocalcemia (70%). Cinacalcet was stopped without achieving the target parathyroid hormone in more than half (55%) of children because of intractable adverse effects (40%), poor response (30%), non-adherence (25%), or high cost (5%).

CONCLUSION

Cinacalcet is used by the majority of pediatric nephrologists in KSA and GCC. A standard clinical guideline is needed to be followed by all users.

A Functional Parathyroid Cyst from the Hemorrhagic Degeneration of a Parathyroid Adenoma

A 77-year-old man with a history of hypertension, prostate hyperplasia, and urolithiasis was admitted for acute kidney injury caused by hypercalcemia. Neck ultrasonography showed a large cyst adjacent to the right lower thyroid lobe. Although a ^99mtechnetium sestamibi scan was negative, an extremely high intracystic intact parathyroid hormone level suggested that the cyst had a parathyroid origin and that a functional parathyroid cyst was present. Immunohistochemical staining for the calcium-sensing receptor (CaSR) after right lower parathyroidectomy revealed CaSR-positive cells lining the cyst, indicating that the functional parathyroid cyst had originated from the hemorrhagic degeneration of a parathyroid adenoma.

[Long-term efficacy of parathyroidectomy in secondary and tertiary hyperparathyroidism]

BACKGROUND

Secondary and tertiary hyperparathyroidism (SHPT and THPT), are complications of chronic kidney disease (CKD), characterized by high levels of serum parathormone, hyperphosphatemia or hypercalcemia, respectively. If diet and pharmacological therapies fail, clinical practice guidelines suggest parathyroidectomy (PTX). Some studies have described its effectiveness and safety, but these have not included Mexican population.

OBJECTIVE

To describe long-term effectiveness of PTX in Mexican patients with SHPT or THPT.

MATERIAL AND METHODS

Observational and retrospective study of patients treated with PTX between 1995 and 2014 in a third level hospital in Mexico City. The analyses included the follow-up of medical treatment and biochemical assessment every three months during the first year, and the last evaluation. Permutation and chi square tests were used.

RESULTS

The study included 27 patients (14 women). The follow-up mean was 39 months; 61.5% had SHPT. All biochemical parameters, except magnesium, were reduced in the first year of follow-up. In the long term, SHPT was controlled in 80% using PTH under a 300 pg/mL criterion, and 90% in patients with THPT using calcium criterion. Persistent hypocalcemia was present in 11.5% of cases.

CONCLUSION

Mexican patients with SHPT and THPT could be successfully treated with surgery with low risk of hypocalcemia.

Hyperparathyroidism and parathyroidectomy in X-linked hypophosphatemia patients

BACKGROUND

X-linked hypophosphatemia (XLH) causes rickets, osteomalacia, skeletal deformities and growth impairment, due to elevated fibroblast growth factor 23 and hypophosphatemia. Conventional therapy requires high doses of phosphate salts combined with active vitamin D analogues. Risks of this regimen include nephrocalcinosis and secondary hyperparathyroidism or progression to tertiary (hypercalcemic) hyperparathyroidism.

METHODS

The primary goals were to estimate the prevalence of hyperparathyroidism and to characterize parathyroidectomy outcomes regarding hypercalcemia among XLH patients. XLH patients attending our center from 1/2000 to 12/2017 were included in a retrospective chart review. Prevalence of nephrocalcinosis and eGFR < 60 ml/min/1.73m2 was also assessed.

RESULTS

Of 104 patients with XLH, 84 had concurrent measurements of calcium and PTH (40 adults and 44 children). Of these, 70/84 (83.3%), had secondary or tertiary hyperparathyroidism at any time point. Secondary hyperparathyroidism was persistent in 62.2% of those with data at multiple timepoints. Tertiary hyperparathyroidism had an overall prevalence of 14/84 (16.7%) patients. Parathyroidectomy was performed in 8/84 (9.5%) of the total population. After parathyroidectomy, persistent or recurrent tertiary hyperparathyroidism was detected in 6/8 (75%) patients at a median of 6 years (from 0 to 29 years). One patient had chronic post-surgical hypoparathyroidism and one patient remained normocalcemic 4 years after surgery. Nephrocalcinosis was more prevalent in patients with tertiary hyperparathyroidism than those without (60.0% vs 18.6%). Chronic kidney disease (eGFR < 60 ml/min/1.73m2) was also more prevalent in patients with tertiary hyperparathyroidism than those without (35.7% vs 1.5%).

CONCLUSION

The majority of patients with XLH develop secondary hyperparathyroidism during treatment with phosphate and active vitamin D. A significant proportion develops tertiary hyperparathyroidism and most have recurrence or persistence of hypercalcemia after surgery.

Effect of Cinacalcet in Kidney Transplant Patients With Hyperparathyroidism

OBJECTIVE

In dialysis patients, cinacalcet could be an effective alternative to parathyroidectomy for treating hyperparathyroidism. In the present study, we aimed to determine the characteristics of subjects with persistent hyperparathyroidism who require parathyroidectomy despite the use of cinacalcet.

METHODS

Nine kidney transplant patients (7 men, 2 women; mean age 53.2 [SD, 8.9] years) who had tertiary hyperparathyroidism were reviewed in a single center. Pre- and postcinacalcet levels of calcium, phosphorous, intact parathyroid hormone (iPTH), and renal function were analyzed to evaluate the effect of cinacalcet treatment in these patients. The baseline parameters before cinacalcet treatment were compared in patients who did and did not undergo parathyroidectomy.

RESULTS

Cinacalcet reduced serum calcium levels in all patients (11.48 [SD, 0.73] mg/dL to 10.20 [0.70] mg/dL; P = .008). Serum phosphorous levels significantly increased from 2.28 (SD, 0.77) mg/dL to 3.02 (SD, 0.65) mg/dL (P = .03). The iPTH levels in 7 patients decreased, while the mean level remained unchanged in total subjects. The iPTH levels increased even with cinacalcet treatment in 2 patients. In 3 patients, serum calcium levels abruptly increased after cinacalcet withdrawal. Five patients who showed persistent hypercalcemia due to hyperparathyroidism underwent parathyroidectomy. These 5 patients had significantly different characteristics compared with 4 patients who did not undergo parathyroidectomy: hypercalcemia (11.92 [SD, 0.68] mg/dL vs 10.93 [SD, 0.26] mg/dL; P = .02), hypophosphatemia (1.74 [SD, 0.36] mg/dL vs 2.95 [SD, 0.58] mg/dL; P = .03), and hyperparathyroidism (252.2 [SD, 131.4] pg/dL vs 101.5 [SD, 18.4] pg/dL; P = .02).

CONCLUSION

Cinacalcet reduced hypercalcemia due to hyperparathyroidism in the transplant patients. However, patients who had pre-existing higher iPTH, hypercalcemia, and hypophosphatemia needed parathyroidectomy. Therefore, cinacalcet could be considered an alternative to parathyroidectomy in selected patients.

Brown tumor of the thoracic spine presenting with paraplegia in a patient with peritoneal dialysis

Secondary and tertiary hyperparathyroidism is an important problem of chronic kidney disease. Brown tumor is a benign, unusual, reactive lesion as a result of disturbed bone remodeling, from long-standing increase in parathyroid hormone level. Brown tumors may cause morbidity due to pressure symptoms on neural structures and spontaneous bone fractures. Herein, we presented a peritoneal dialysis patient with tertiary hyperparathyroidism under calcand calcitriol treatment for 4 years due to refusing of the parathyroidectomy operation. She admitted to hospital for sudden onset back pain with difficulty in gait and walking, and imaging studies showed an expansile mass lesion in the thoracic spine. She was operated for mass and diagnosed with brown tumor. After operation, she lost the ability of walking than become paraplegic and she underwent rehabilitation program. Preventive measures including calcitriol and cinacalcet may cause a modest decrease in parathyroid hormone levels but it should be remembered for the development of bone complications such as brown tumor formation in patients with moderate elevated PTH levels, especially those with tertiary hyperparathyroidism. Parathyroidectomy should be performed without delay in these cases.

Effect of Endogenous Parathyroid Hormone on Bone Geometry and Skeletal Microarchitecture

Parathyroid hormone (PTH) has anabolic or catabolic effects on bones; however, the skeletal effect of endogenous PTH on cortical and trabecular bones is not yet clear. Therefore, we aimed to examine the effects of an excess and a deficiency of endogenous PTH on the lumbar spine trabecular bone score (TBS) and bone geometry using dual-energy X-ray absorptiometry. We retrospectively included 70 patients with primary hyperparathyroidism (PHPT), 26 patients with idiopathic or postoperative hypoparathyroidism (HypoPT), and 96 normal controls matched by age, sex, and body mass index. The bone mineral density (BMD) at the lumbar spine, femur neck, and total hip was higher in the HypoPT, followed by the controls and PHPT group (all P < 0.001). The TBS was significantly decreased in the PHPT group compared to the controls (P = 0.021); however, statistical significance disappeared after adjusting for the lumbar BMD (P = 0.653). There were no significant differences in the TBS between the HypoPT group and controls as well as the PHPT and HypoPT group. As for bone geometry parameters, the cross-sectional area, cross-sectional moment of inertia, and section modulus were higher in the HypoPT, followed by the controls and PHPT group (all P < 0.001); statistical significance remained after adjusting for the total hip BMD. We also observed a significantly increased cortical neck width in the HypoPT group compared to the PHPT group (P = 0.009). The buckling ratio was higher in the PHPT than the HypoPT group and controls (P = 0.018 and P = 0.013, respectively). The present study demonstrated that an excess of endogenous PTH had catabolic effects on both cortical and trabecular bones. Under conditions of endogenous PTH deficiency, the effect on cortical bone was pronounced, but that on trabecular bone was modest.

Use of calcimimetics in children with normal kidney function

The calcium-sensing receptor (CaSR) plays an important role in the homeostasis of serum ionized calcium by regulating parathyroid hormone (PTH) secretion and tubular calcium handling. Calcimimetics, which act by allosteric modulation of the CaSR, mimic hypercalcemia resulting in suppression of PTH release and increase in calciuria. Mostly used in children to treat secondary hyperparathyroidism associated with advanced renal failure, we have shown that calcimimetics can also be successfully used in children with bone and mineral disorders in which elevated PTH plays a detrimental role in skeletal pathophysiology in the face of normal kidney function. The current review briefly discusses the role of the CaSR and calcimimetics in calcium homeostasis, and then addresses the potential applications of calcimimetics in children with normal kidney function with disorders in which suppression of PTH is beneficial.

Parathyroid Hormone Fragments: New Targets for the Diagnosis and Treatment of Chronic Kidney Disease-Mineral and Bone Disorder

As a common disorder, chronic kidney disease (CKD) poses a great threat to human health. Chronic kidney disease-mineral and bone disorder (CKD-MBD) is a complication of CKD characterized by disturbances in the levels of calcium, phosphorus, parathyroid hormone (PTH), and vitamin D; abnormal bone formation affecting the mineralization and linear growth of bone; and vascular and soft tissue calcification. PTH reflects the function of the parathyroid gland and also takes part in the metabolism of minerals. The accurate measurement of PTH plays a vital role in the clinical diagnosis, treatment, and prognosis of patients with secondary hyperparathyroidism (SHPT). Previous studies have shown that there are different fragments of PTH in the body's circulation, causing antagonistic effects on bone and the kidney. Here we review the metabolism of PTH fragments; the progress being made in PTH measurement assays; the effects of PTH fragments on bone, kidney, and the cardiovascular system in CKD; and the predictive value of PTH measurement in assessing the effectiveness of parathyroidectomy (PTX). We hope that this review will help to clarify the value of accurate PTH measurements in CKD-MBD and promote the further development of multidisciplinary diagnosis and treatment.

Mineralocorticoid Receptor Blockers and Aldosterone to Renin Ratio: A Randomized Controlled Trial and Observational Data

Current guidelines recommend to withdraw mineralocorticoid receptor (MR) blocker treatment for at least 4 weeks when measuring the aldosterone to renin ratio (ARR) as a screening test for primary aldosteronism (PA). We aimed to evaluate the effect of MR blocker treatment on ARR and its components, plasma aldosterone concentration (PAC), and direct renin concentration (DRC). First, we performed a post-hoc analysis of the effect of eplerenone on parathyroid hormone levels in primary hyperparathyroidism (EPATH) study, a randomized controlled trial (RCT) in 110 patients with primary hyperparathyroidism (pHPT). Patients were 1:1 randomly assigned to receive either 25 mg eplerenone once daily (up-titration after 4 weeks to 50 mg/day) or placebo for 8 weeks. Second, we measured the ARR in 4 PA patients from the Graz Endocrine Causes of Hypertension Study (GECOH) before and after MR blocker treatment. Ninety-seven participants completed the EPATH trial, and the mean treatment effect (95% confidence interval) for log(e)ARR was 0.08 (-0.32 to 0.48) ng/dl/μU/ml (p=0.694). The treatment effect was 0.71 (0.47 to 0.96; p<0.001) ng/dl for log(e)PAC and 0.64 (0.19 to 1.10; p=0.006) μU/ml for log(e)DRC, respectively. In the 4 PA patients, the ARR decreased from 11.24±3.58 at baseline to 2.70±1.03 (p=0.013) ng/dl/μU/ml after MR blocker treatment. In this study with limited sample size, MR blocker treatment did not significantly alter the ARR in pHPT patients but significantly reduced the ARR in PA patients. Diagnostic utility of ARR and its components for PA diagnostics under MR blocker treatment warrants further study.

The Use of Vitamin D Metabolites and Analogues in the Treatment of Chronic Kidney Disease

Chronic kidney disease (CKD) and end-stage renal disease (ESRD) are associated with abnormalities in bone and mineral metabolism, known as CKD-bone mineral disorder. CKD and ESRD cause skeletal abnormalities characterized by hyperparathyroidism, mixed uremic osteodystrophy, osteomalacia, adynamic bone disease, and frequently enhanced vascular and ectopic calcification. Hyperparathyroidism and mixed uremic osteodystrophy are the most common manifestations due to phosphate retention, reduced concentrations of 1,25-dihydroxyvitamin D, intestinal calcium absorption, and negative calcium balance. Treatment with 1-hydroxylated vitamin D analogues is useful.

Thiazide Treatment in Primary Hyperparathyroidism-A New Indication for an Old Medication?

CONTEXT

There is no therapy for control of hypercalciuria in nonoperable patients with primary hyperparathyroidism (PHPT). Thiazides are used for idiopathic hypercalciuria but are avoided in PHPT to prevent exacerbating hypercalcemia. Nevertheless, several reports suggested that thiazides may be safe in patients with PHPT.

OBJECTIVE

To test the safety and efficacy of thiazides in PHPT.

DESIGN

Retrospective analysis of medical records.

SETTING

Endocrine clinic at a tertiary hospital.

PATIENTS

Fourteen male and 58 female patients with PHPT treated with thiazides.

INTERVENTIONS

Data were compared for each patient before and after thiazide administration.

MAIN OUTCOME MEASURES

Effect of thiazide on urine and serum calcium levels.

RESULTS

Data are given as mean ± standard deviation. Treatment with hydrochlorothiazide 12.5 to 50 mg/d led to a decrease in mean levels of urine calcium (427 ± 174 mg/d to 251 ± 114 mg/d; P < 0.001) and parathyroid hormone (115 ± 57 ng/L to 74 ± 36 ng/L; P < 0.001), with no change in serum calcium level (10.7 ± 0.4 mg/dL off treatment, 10.5 ± 1.2 mg/dL on treatment, P = 0.4). Findings were consistent over all doses, with no difference in the extent of reduction in urine calcium level or change in serum calcium level by thiazide dose.

CONCLUSION

Thiazides may be effective even at a dose of 12.5 mg/d and safe at doses of up to 50 mg/d for controlling hypercalciuria in patients with PHPT and may have an advantage in decreasing serum parathyroid hormone level. However, careful monitoring for hypercalcemia is required.

Use of Extended-Release Calcifediol to Treat Secondary Hyperparathyroidism in Stages 3 and 4 Chronic Kidney Disease

BACKGROUND/AIMS

Vitamin D insufficiency and secondary hyperparathyroidism (SHPT) are associated with increased morbidity and mortality in chronic kidney disease (CKD) and are poorly addressed by current treatments. The present clinical studies evaluated extended-release (ER) calcifediol, a novel vitamin D prohormone repletion therapy designed to gradually correct low serum total 25-hydroxyvitamin D, improve SHPT control and minimize the induction of CYP24A1 and FGF23.

METHODS

Two identical multicenter, randomized, double-blind, placebo-controlled studies enrolled subjects from 89 US sites. A total of 429 subjects, balanced between studies, with stage 3 or 4 CKD, SHPT and vitamin D insufficiency were randomized 2:1 to receive oral ER calcifediol (30 or 60 µg) or placebo once daily at bedtime for 26 weeks. Most subjects (354 or 83%) completed dosing, and 298 (69%) entered a subsequent open-label extension study wherein ER calcifediol was administered without interruption for another 26 weeks.

RESULTS

ER calcifediol normalized serum total 25-hydroxyvitamin D concentrations (>30 ng/ml) in >95% of per-protocol subjects and reduced plasma intact parathyroid hormone (iPTH) by at least 10% in 72%. The proportion of subjects receiving ER calcifediol who achieved iPTH reductions of ≥30% increased progressively with treatment duration, reaching 22, 40 and 50% at 12, 26 and 52 weeks, respectively. iPTH lowering with ER calcifediol was independent of CKD stage and significantly greater than with placebo. ER calcifediol had inconsequential impact on serum calcium, phosphorus, FGF23 and adverse events.

CONCLUSION

Oral ER calcifediol is safe and effective in treating SHPT and vitamin D insufficiency in CKD.

Vitamin D deficiency masking primary hyperparathyroidism

Vitamin D deficiency and primary hyperparathyroidism (PHPT) are relatively common disorders. The coexistence of these conditions should be considered, as depletion of vitamin D may alter the clinical expression of autonomous parathyroid disease. We report details of a vitamin D deficient patient in whom replacement therapy led to the unmasking of occult PHPT.

GENETICS IN ENDOCRINOLOGY: Gain and loss of function mutations of the calcium-sensing receptor and associated proteins: current treatment concepts

The calcium-sensing receptor (CASR) is the main calcium sensor in the maintenance of calcium metabolism. Mutations of the CASR, the G protein alpha 11 (GNA11) and the adaptor-related protein complex 2 sigma 1 subunit (AP2S1) genes can shift the set point for calcium sensing causing hyper- or hypo-calcemic disorders. Therapeutic concepts for these rare diseases range from general therapies of hyper- and hypo-calcemic conditions to more pathophysiology oriented approaches such as parathyroid hormone (PTH) substitution and allosteric CASR modulators. Cinacalcet is a calcimimetic that enhances receptor function and has gained approval for the treatment of hyperparathyroidism. Calcilytics in turn attenuate CASR activity and are currently under investigation for the treatment of various diseases. We conducted a literature search for reports about treatment of patients harboring inactivating or activating CASR, GNA11 or AP2S1 mutants and about in vitro effects of allosteric CASR modulators on mutated CASR. The therapeutic concepts for patients with familial hypocalciuric hypercalcemia (FHH), neonatal hyperparathyroidism (NHPT), neonatal severe hyperparathyroidism (NSHPT) and autosomal dominant hypocalcemia (ADH) are reviewed. FHH is usually benign, but symptomatic patients benefit from cinacalcet. In NSHPT patients pamidronate effectively lowers serum calcium, but most patients require parathyroidectomy. In some patients cinacalcet can obviate the need for surgery, particularly in heterozygous NHPT. Symptomatic ADH patients respond to vitamin D and calcium supplementation but this may increase calciuria and renal complications. PTH treatment can reduce relative hypercalciuria. None of the currently available therapies for ADH, however, prevent tissue calcifications and complications, which may become possible with calcilytics that correct the underlying pathophysiologic defect.

Calcimimetic and Calcilytic Drugs: Feats, Flops, and Futures

The actions of extracellular Ca(2+) in regulating parathyroid gland and kidney functions are mediated by the extracellular calcium receptor (CaR), a G protein-coupled receptor. The CaR is one of the essential molecules maintaining systemic Ca(2+) homeostasis and is a molecular target for drugs useful in treating bone and mineral disorders. Ligands that activate the CaR are termed calcimimetics and are classified as either agonists (type I) or positive allosteric modulators (type II); calcimimetics inhibit the secretion of parathyroid hormone (PTH). Cinacalcet is a type II calcimimetic that is used to treat secondary hyperparathyroidism in patients receiving dialysis and to treat hypercalcemia in some forms of primary hyperparathyroidism. The use of cinacalcet among patients with secondary hyperparathyroidism who are managed with dialysis effectively lowers circulating PTH levels, reduces serum phosphorus and FGF23 concentrations, improves bone histopathology, and may diminish skeletal fracture rates and the need for parathyroidectomy. A second generation type II calcimimetic (AMG 416) is currently under regulatory review. Calcilytics are CaR antagonists that stimulate the secretion of PTH. Several calcilytic compounds have been evaluated as orally active anabolic therapies for postmenopausal osteoporosis but clinical development of all of them has been abandoned because they lacked clinical efficacy. Calcilytics might be repurposed for new indications like autosomal dominant hypocalcemia or other disorders beyond those involving systemic Ca(2+) homeostasis.

Pre-operative fibrous osteodystrophy and severe, refractory, post-operative hypocalcemia following parathyroidectomy in a dog

A 13-year-old dog exhibited dramatic, radiographic osteopenia consistent with fibrous osteodystrophy secondary to primary hyperparathyroidism. Following parathyroidectomy, the dog developed severe, prolonged hypocalcemia, but was successfully treated and discharged 32 d after surgery. A variety of factors may have contributed to this dog's hypocalcemia including hypoparathyroidism and hungry bone syndrome.

Cinacalcet normalizes serum calcium in a double-blind randomized, placebo-controlled study in patients with primary hyperparathyroidism with contraindications to surgery

OBJECTIVE

Primary hyperparathyroidism (PHPT) is diagnosed by the presence of hypercalcemia and elevated or nonsuppressed parathyroid hormone (PTH) levels. Although surgery is usually curative, some individuals fail or are unable or unwilling to undergo parathyroidectomy. In such individuals, targeted medical therapy may be of value. Cinacalcet normalized calcium level and lowered PTH in patients with PHPT in several phase 2 and open-label studies. We compared cinacalcet and placebo in subjects with PHPT unable to undergo parathyroidectomy.

DESIGN

Phase 3, double-blind, multi centere, randomized, placebo-controlled study.

METHODS

Sixty-seven subjects (78% women) with moderate PHPT were randomized (1:1) to cinacalcet or placebo for ≤28 weeks.

MAIN OUTCOME MEASURE

Achievement of a normal mean corrected total serum calcium concentration of ≤10.3 mg/dl (2.575 mmol/l).

RESULTS

Baseline median (quartile 1 (Q1), Q3) serum PTH was 164.0 (131.0, 211.0) pg/ml and mean (s.d.) serum Ca was 11.77 (0.46) mg/dl. Serum Ca normalized (≤10.3 mg/dl) in 75.8% of cinacalcet- vs 0% of placebo-treated subjects (P<0.001). Corrected serum Ca decreased by ≥1.0 mg/dl from baseline in 84.8% of cinacalcet- vs 5.9% of placebo-treated subjects (P<0.001). Least squares mean (s.e.m.) plasma PTH change from baseline was -23.80% (4.18%) (cinacalcet) vs -1.01% (4.05%) (placebo) (P<0.001). Similar numbers of subjects in the cinacalcet and placebo groups reported adverse events (AEs) (27 vs 20) and serious AEs (three vs four). Most commonly reported AEs were nausea and muscle spasms.

CONCLUSIONS

These results demonstrate that cinacalcet normalizes serum calcium in this PHPT population and appears to be well tolerated.

Effect of paricalcitol on circulating parathyroid hormone in X-linked hypophosphatemia: a randomized, double-blind, placebo-controlled study

CONTEXT

Hyperparathyroidism occurs frequently in X-linked hypophosphatemia (XLH) and may exacerbate phosphaturia, potentially affecting skeletal abnormalities.

OBJECTIVE

The objective of the study was to suppress elevated PTH levels in XLH patients.

DESIGN

This was a prospective, randomized, placebo-controlled, double-blind, 1-year trial of paricalcitol, with outcomes measured at entry and 1 year later.

SETTING

PATIENTS were recruited from the investigators' clinics or referred from throughout the United States. Data were collected in an in-patient hospital research unit.

PATIENTS

Subjects with a clinical diagnosis of XLH and hyperparathyroidism were offered participation and were eligible if they were 9 years old or older and not pregnant, and their serum calcium level was less than 10.7 mg/dL, their 25-hydroxyvitamin D level was 20 ng/mL or greater, and their creatinine level was 1.5 mg/dL or less.

INTERVENTION

The intervention for this study was the use of paricalcitol or placebo for 1 year.

MAIN OUTCOME MEASURES

Determined prior to trial onset was the change in PTH area under the curve. Secondary outcomes included renal phosphate threshold per glomerular filtration rate, serum phosphorus, serum alkaline phosphatase activity, and (99m)Tc-methylenediphosphonate bone scans.

RESULTS

PTH area under the curve decreased 17% with paricalcitol, differing (P = .007) from the 20% increase with placebo. The renal phosphate threshold per glomerular filtration rate increased 17% with paricalcitol and decreased 21% with placebo (P = .05). Serum phosphorus increased 12% with paricalcitol but did not differ from placebo. Paricalcitol decreased alkaline phosphatase activity in adults by 21% (no change with placebo, P = .04). Bone scans improved in 6 of 17 paricalcitol subjects, whereas no placebo-treated subject improved. Hypercalciuria developed in six paricalcitol subjects and persisted from baseline in one placebo subject.

CONCLUSIONS

Suppression of PTH may be a useful strategy for skeletal improvement in XLH patients with hyperparathyroidism, and paricalcitol appears to be an effective adjunct to standard therapy in this setting. Although paricalcitol was well tolerated, urinary calcium and serum calcium and creatinine should be monitored closely with its use.

Mechanisms in endocrinology: vitamin D as a potential contributor in endocrine health and disease

OBJECTIVE

It has been suggested that vitamin D may play a role in the pathogenesis of several endocrine diseases, such as hyperparathyroidism, type 1 diabetes (T1DM), type 2 diabetes (T2DM), autoimmune thyroid diseases, Addison's disease and polycystic ovary syndrome (PCOS). In this review, we debate the role of vitamin D in the pathogenesis of endocrine diseases.

METHODS

Narrative overview of the literature synthesizing the current evidence retrieved from searches of computerized databases, hand searches and authoritative texts.

RESULTS

Evidence from basic science supports a role for vitamin D in many endocrine conditions. In humans, inverse relationships have been reported not only between blood 25-hydroxyvitamin D and parathyroid hormone concentrations but also with risk of T1DM, T2DM, and PCOS. There is less evidence for an association with Addison's disease or autoimmune thyroid disease. Vitamin D supplementation may have a role for prevention of T2DM, but the available evidence is not consistent.

CONCLUSIONS

Although observational studies support a potential role of vitamin D in endocrine disease, high quality evidence from clinical trials does not exist to establish a place for vitamin D supplementation in optimizing endocrine health. Ongoing randomized controlled trials are expected to provide insights into the efficacy and safety of vitamin D in the management of endocrine disease.

Novel homozygous inactivating mutation of the calcium-sensing receptor gene (CASR) in neonatal severe hyperparathyroidism-lack of effect of cinacalcet

BACKGROUND

NSHPT is a life-threatening disorder caused by homozygous inactivating calcium-sensing receptor (CASR) mutations. In some cases, the CaSR allosteric activator, cinacalcet, may reduce serum PTH and calcium levels, but surgery is the treatment of choice.

OBJECTIVE

To describe a case of NSHPT unresponsive to cinacalcet.

PATIENT AND RESULTS

A 23-day-old girl was admitted with hypercalcemia, hypotonia, bell-shaped chest and respiratory distress. The parents were first-degree cousins once removed. Serum Ca was 4.75 mmol/l (N: 2.10-2.62), P: 0.83 mmol/l (1.55-2.64), PTH: 1096 pg/ml (9-52) and urinary Ca/Cr ratio: 0.5mg/mg. First, calcitonin was given (10 IU/kg × 4/day), and then 2 days later, pamidronate (0.5mg/kg) for 2 days. Doses of cinacalcet were given daily from day 28 of life starting at 30 mg/m2 and increasing to 90 mg/m2 on day 43. On day 33, 6 days after pamidronate, serum Ca levels had fallen to 2.5 mmol/l but, thereafter, rose to 5 mmol/l despite the cinacalcet. Total parathyroidectomy was performed at day 45. Hungry bone disease after surgery required daily Ca replacement and calcitriol for 18 days. At 3 months, the girl was mildly hypercalcemic, with no supplementation, and at 6 months, she developed hypocalcemia and has since been maintained on Ca and calcitriol. By CASR mutation analysis, the infant was homozygous and both parents heterozygous for a deletion-frameshift mutation.

CONCLUSION

The predicted nonfunctional CaSR is consistent with lack of response to cinacalcet, but total parathyroidectomy was successful. An empiric trial of the drug and/or prompt mutation testing should help minimize the period of unnecessary pharmacotherapy.

Vitamin D treatment in primary hyperparathyroidism: a randomized placebo controlled trial

CONTEXT

Low 25-hydroxyvitamin D levels are common in patients with primary hyperparathyroidism (PHPT) and associated with higher PTH levels and hungry bone syndrome after parathyroidectomy (PTX). However, concerns have been raised about the safety of vitamin D supplementation in PHPT.

OBJECTIVE

We aimed to assess safety and effects on calcium homeostasis and bone metabolism of supplementation with high doses of vitamin D in PHPT patients.

DESIGN, SETTING

This was an investigator-initiated double-blind, randomized, placebo-controlled, parallel-group trial from a single center.

PATIENTS

Forty-six PHPT patients were recruited, with a mean age of 58 (range 29-77) years, and 35 (76%) were women.

INTERVENTIONS

Intervention included daily supplementation with 70 μg (2800 IU) cholecalciferol or identical placebo for 52 weeks. Treatment was administered 26 weeks before PTX and continued for 26 weeks after PTX.

MAIN OUTCOME MEASURES

PTH, calcium homeostasis, and bone metabolism were evaluated.

RESULTS

Preoperatively, 25-hydroxyvitamin D increased from 50 to 94 nmol/L in the treatment group and decreased from 57 to 52 nmol/L in the placebo group (P < .001). Compared with placebo, vitamin D decreased PTH significantly by 17% before PTX (P = .01), increased lumbar spine bone mineral density by 2.5% (P = .01), and decreased C-terminal β-CrossLaps by 22% (P < .005). The trabecular bone score did not change in response to treatment, but improved after PTX. Postoperatively, PTH remained lower in the cholecalciferol group compared with the placebo group (P = .04). Plasma creatinine and plasma and urinary calcium did not differ between groups.

CONCLUSIONS

Daily supplementation with a high vitamin D dose safely improves vitamin D status and decreases PTH in PHPT patients. The vitamin D treatment is accompanied by reduced bone resorption and improved bone mineral density before operation.

The EVOLVE study is negative, so what does this 'bitter pill' of disappointment mean now for renal patients?

The extremely high morbidity and mortality experienced by subjects with chronic kidney disease (CKD) has often been described and reviewed, but this familiarity should not breed indifference to the huge burden of premature cardiovascular disease – something which becomes more obvious, but increasingly challenging to treat, as GFR declines, or proteinuria increases. The health outcomes for a middle-aged person entering renal replacement therapy are as bad as those seen with a major solid organ malignancy; while there has been modest progress in improving outcomes over the last two decades, the diagnosis of significant or progressive CKD should and thus still does continue to cast a shadow over patients, carers and healthcare professionals alike.

Cinacalcet monotherapy in neonatal severe hyperparathyroidism: a case study and review

CONTEXT

Neonatal severe hyperparathyroidism (NSHPT) is a severe form of familial hypocalciuric hypercalcemia characterized by severe hypercalcemia and skeletal demineralization. In most cases, NSHPT is due to biallelic loss-of-function mutations in the CASR gene encoding the calcium-sensing receptor (CaSR), but some patients have heterozygous mutations. Conventional treatment consists of iv saline, bisphosphonates, and parathyroidectomy.

OBJECTIVE

The aim of this project was to characterize the molecular basis for NSHPT in an affected newborn and to describe the response to monotherapy with cinacalcet.

METHODS

Clinical and biochemical features were monitored as cinacalcet therapy was initiated and maintained. Genomic DNA was obtained from the proband and parents. The CASR gene was amplified by PCR and sequenced directly.

RESULTS

The patient was a full-term male who developed hypotonia and respiratory failure soon after birth. He was found to have multiple fractures and diffuse bone demineralization, with a marked elevation in serum ionized calcium (1.99 mmol/L) and elevated serum levels of intact PTH (1154 pg/mL); serum 25-hydroxyvitamin D was low, and fractional excretion of calcium was reduced. The serum calcium level was not reduced by iv saline infusion. Based on an extensive family history of autosomal dominant hypercalcemia, a diagnosis of NSHPT was made, and cinacalcet therapy was initiated with a robust and durable effect. Molecular studies revealed a heterozygous R185Q missense mutation in the CASR in the patient and his father, whereas normal sequences for the CASR gene were present in the patient's mother.

CONCLUSIONS

We describe the first use of cinacalcet as monotherapy for severe hypercalcemia in a newborn with NSHPT. The rapid and durable response to cinacalcet suggests that a trial of calcimimetic therapy should be considered early in the course of NSHPT.

What can we learn from a statistically inconclusive trial? Consensus conference on the EVOLVE study results

The link between serum parathyroid hormone (iPTH) and cardiovascular (CVS) mortality has not been fully elucidated. The EVOLVE Study was designed to test whether a drug such as cinacalcet, aimed at lowering iPTH, could reduce the astonishingly high cardiovascular risk in patients on maintenance dialysis (CKD-5D). Accordingly, the primary outcome of the study was the combined endpoint of time to death or hospitalization due to CVS factors or from any cause. Time to bone fracture and parathyroidectomy were regarded as secondary endpoints. At study completion, the Intention-To-Treat analysis documented a non- significant 7% (Hazard Ratio: 0.93; 95% Confidence interval: 0.85-1.02; P = 0.11) reduction of the primary composite endpoint. However, the intention to treat analysis does not take into account adherence to drug regimens or control for factors that may potentially jeopardize the conduction of the study. In particular, in spite of a careful pre-planned study sample calculation, the final power of the EVOLVE study was 54% instead of the assumed 90%, greatly reducing the reliability of study results. Furthermore, the pre-planned multivariable adjustment of the primary endpoint suggests a nominally significant reduction of the risk of the primary composite endpoint when age is entered into the statistical model. The sensitivity analysis further corroborates this result. The Lag Time Censoring Analysis (LTCA) evidenced a nominally significant 15% risk reduction of the composite endpoint among patients allocated to cinacalcet if the patients follow-up was terminated 6 months after the study drug discontinuation, as pre-planned in the protocol. It is interesting that the LTCA suggests that the effect of cinacalcet weakened over time and became insignificant after about 1 year from drug discontinuation. Although authors could not detect any effect of cinacalcet on bone fracture associated with cinacalcet use, the secondary analyses of the EVOLVE trial suggest a nominally significant 60-70% risk reduction of parathyroidectomy and a reassuring safety profile of prolonged exposure to cinacalcet. In summary, the EVOLVE study adds to the list of inconclusive randomized clinical trials in Nephrology. However, the preplanned exploratory and sensitivity analyses suggest that when imbalances of patients characteristics at study entry (i.e. age) or study drug discontinuation are considered, a 'nominally' significant risk reduction in CVS and parathyroidectomy associated with cinacalcet treatment is noted.

Secondary and tertiary hyperparathyroidism

We reviewed the etiology and management of secondary and tertiary hyperparathyroidism. Secondary hyperparathyroidism is characterized by an increase in parathyroid hormone (PTH) that is appropriate and in response to a stimulus, most commonly low serum calcium. In secondary hyperparathyroidism, the serum calcium is normal and the PTH level is elevated. Tertiary hyperparathyroidism is characterized by excessive secretion of PTH after longstanding secondary hyperparathyroidism, in which hypercalcemia has ensued. Tertiary hyperparathyroidism typically occurs in men and women with chronic kidney disease usually after kidney transplant. The etiology and treatment of secondary hyperparathyroidism is relatively straightforward whereas data on the management of tertiary hyperparathyroidism is limited to a few small trials with short follow-up.

Cinacalcet in patients with chronic kidney disease: a cumulative meta-analysis of randomized controlled trials

BACKGROUND

Calcimimetic agents lower serum parathyroid hormone levels in people with chronic kidney disease (CKD), but treatment effects on patient-relevant outcomes are uncertain. We conducted a systematic review and meta-analysis to summarize the benefits and harms of calcimimetic therapy in adults with CKD and used cumulative meta-analysis to identify how evidence for calcimimetic treatment has developed in this clinical setting.

METHODS AND FINDINGS

Cochrane and Embase databases (through February 7, 2013) were electronically searched to identify randomized trials evaluating effects of calcimimetic therapy on mortality and adverse events in adults with CKD. Two independent reviewers identified trials, extracted data, and assessed risk of bias. Eighteen trials comprising 7,446 participants compared cinacalcet plus conventional therapy with placebo or no treatment plus conventional therapy in adults with CKD. In moderate- to high-quality evidence (based on Grading of Recommendations Assessment, Development, and Evaluation criteria) in adults with CKD stage 5D (dialysis), cinacalcet had little or no effect on all-cause mortality (relative risk, 0.97 [95% confidence interval, 0.89-1.05]), had imprecise effect on cardiovascular mortality (0.67 [0.16-2.87]), and prevented parathyroidectomy (0.49 [0.40-0.59]) and hypercalcemia (0.23 [0.05-0.97]), but increased hypocalcemia (6.98 [5.10-9.53]), nausea (2.02 [1.45-2.81]), and vomiting (1.97 [1.73-2.24]). Data for clinical outcomes were sparse in adults with CKD stages 3-5. On average, treating 1,000 people with CKD stage 5D for 1 y had no effect on survival and prevented about three patients from experiencing parathyroidectomy, whilst 60 experienced hypocalcemia and 150 experienced nausea. Analyses were limited by insufficient data in CKD stages 3-5 and kidney transplant recipients.

CONCLUSIONS

Cinacalcet reduces the need for parathyroidectomy in patients with CKD stage 5D, but does not appear to improve all-cause or cardiovascular mortality. Additional trials in CKD stage 5D are unlikely to change our confidence in the treatment effects of cinacalcet in this population.

[Treatment of mineral bone disorder with pharmaceuticals which influence the calcium phosphor turnover]

This review discusses the mineral bone disorders in patients with chronic kidney disease. We focus on the management of these conditions by administration of calcium, vitamin D (ergocalciferol and cholecalciferol), vitamin D receptor activators (calcitriol, alphacalcidiol), phosphate binders and calcimimetics (cinacalcet).

Restoration of bone mineralization by cinacalcet is associated with a significant reduction in calcitriol-induced vascular calcification in uremic rats

The present study investigated to what extent normalization of bone turnover goes along with a reduction of high-dose calcitriol-induced vascular calcifications in uremic rats. Five groups of male Sprague-Dawley rats were studied: sham-operated controls (n = 7), subtotally nephrectomized (SNX) uremic (CRF) animals (n = 12), CRF + calcitriol (vitD) (0.25 μg/kg/day) (n = 12), CRF + vitD + cinacalcet (CIN) (10 mg/kg/day) (n = 12), and CRF + vitD + parathyroidectomy (PTX) (n = 12). Treatment started 2 weeks after SNX and continued for the next 14 weeks. High-dose calcitriol treatment in hyperparathyroid rats went along with the development of distinct vascular calcification, which was significantly reduced by >50 %, in both CIN-treated and PTX animals. Compared to control animals and those of the CRF group, calcitriol treatment either in combination with CIN or PTX or not was associated with a significant increase in bone area comprising ±50 % of the total tissue area. However, whereas excessive woven bone accompanied by a dramatically increased osteoid width/area was seen in the CRF + vitD group, CIN treatment and PTX resulted in significantly reduced serum PTH level, which was accompanied by a distinct reduction of both the bone formation rate and the amount of osteoid. These data indicate that less efficient calcium and phosphorus incorporation in bone inherent to the severe hyperparathyroidism in vitamin D-treated uremic rats goes along with excessive vascular calcification, a process which is partially reversed by CIN treatment in combination with a more efficacious bone mineralization, thus restricting the availability of calcium and phosphate for being deposited in the vessel wall.

Effects of cinacalcet in renal transplant patients with hyperparathyroidism

BACKGROUND

Cinacalcet decreases serum parathyroid hormone (PTH) and calcium concentrations in kidney transplant recipients with autonomous hyperparathyroidism. Long-term treatment with cinacalcet may increase urinary calcium excretion and the risk of renal calcium deposits and may alter renal graft function.

METHODS

We studied 71 renal recipients with hypercalcemic hyperparathyroidism. Of these patients, 34 received cinacalcet between month 3 and month 12 after renal transplantation. We compared phosphate calcium balance, measured glomerular filtration rate (GFR) and renal biopsies in cinacalcet-treated and non-cinacalcet-treated patients. Measurements were performed before initiating cinacalcet treatment (month 3) and at month 12.

RESULTS

Patients treated with cinacalcet had more severe hyperparathyroidism. Serum PTH concentration decreased in both groups between months 3 and 12, but the decrease was much more important in cinacalcet-treated patients. Urinary calcium excretion significantly increased under cinacalcet treatment and was more than twice as high at month 12 as in patients who did not receive cinacalcet treatment. However, the hypercalciuria was not associated with an increase in calcium deposits on renal biopsies or an alteration of measured GFR.

CONCLUSIONS

Despite sustained and marked hypercalciuria induced by cinacalcet treatment, cinacalcet does not have adverse effects on GFR or on renal graft calcium deposits in the first year following renal transplantation.

A novel dose regimen of cinacalcet in the treatment of severe hyperparathyroidism in hemodialysis patients

During the recent years, cinacalcet has markedly improved the management of hyperparathyroidism in patients on hemodialysis. However, to the best of our knowledge, there are no specific studies addressing the dose regimen of cinacalcet. The aim of the study was to evaluate the efficacy of cinacalcet on the achievement of targets in the treatment of hyperparathyroidism in two different dosage schedules. Twenty-seven adult patients who were on hemodialysis for more than four months and with severe secondary hyperparathyroidism (intact parathyroid hormone (iPTH) >88 pmol/L) resistant to conventional treatment were included in this prospective study. We used the targets of K/DOQI-clinical guidelines as optimal target of iPTH, calcium and phosphate. Group 1 received a single daily administration of 30 mg of cinacalcet along with the main meal as the starting dose, and the dose was titrated thereafter monthly. Group 2 received cinacalcet with the main meal twice weekly starting with a dose of 90 mg on the first day of the week and 120 mg at midweek and titrated thereafter monthly. The levels of iPTH decreased significantly (P = 0.0001) from 124.00 ± 44.77 pmol/L to 37.78 ± 12.49 pmol/L and from 109.61 ± 53.13 pmol/L to 33.93 ± 12.03 pmol/L after 12 weeks in groups 1 and 2, respectively. After 12 weeks, alkaline phosphatase declined significantly (P = 0.0001) from 143.42 ± 75.20 IU/L to 87.42 ± 14.46 IU/L in group 1 (P = 0.013), and from 148.00 ± 108.49 IU/L to 101.61 ± 46.62 IU/L in group 2 (P = 0.05). There were no significant differences between the reductions of iPTH, calcium phosphate product and alkaline phosphatase levels in both the groups in the vertical comparison at the end of the study. There was no noteworthy difference in side effects between both the groups. Our results indicate that cinacalcet twice weekly is reasonably safe and effective in suppressing high PTH levels in hemodialysis patients, with fewer side effects.

Hyperparathyroidism due to auto-immunological malabsorption in an African girl

Hyperparathyroidism is a rare finding in children. It is a typical sign of vitamin D-deficiency caused by different reasons. It may also be due to calcium wasting syndromes, and it can rarely be induced by adenomas of the parathyroid glands and in parathormone receptor mutations (pseudohyperparathyroidism). A 12-year old Gambian girl living in Hamburg, Germany, was developing abdominal and joint pain. Serum analysis revealed low serum-calcium, significantly elevated parathormone and decreased vitamin D. Immigrant rickets was assumed. Because of abdominal pain and iron deficiency, lambliasis was ruled out. Celiac disease was demonstrated by gliadin and endomysium antibodies as well as by intestinal mucosa biopsy. Despite of a gluten-free diet the joint pains persisted. They were declared by rheumatologists to be caused by a chronic juvenile arthritis (sister disease of celiac disease). However, there were no positive inflammation signals and no clear elevated rheuma-immunology. Follow up: Gluten-free diet and additional treatment with calcium and active vitamin D did not stop increasing parathormone levels, did not stop abdominal and joint pain, and did not stop increment of positive celiac disease antibodies. Assuming compliance problems the patient was then treated with vitamin D injections, which caused decreasing parathormone levels and vanishing joint pain. Celiac disease can cause intestinal rickets with elevated parathomone levels mimicking chronic juvenile arthritis, if gluten-free diet is not strictly performed by compliance problems.

Neonatal hyperparathyroidism with a heterozygous calcium-sensing receptor (CASR) R185Q mutation: clinical benefit from cinacalcet

Neonatal hyperparathyroidism can be caused by a heterozygous inactivating mutation in the calcium-sensing receptor. Calcimimetics, allosteric activators of the calcium-sensing receptor, may provide an effective means of reducing PTH secretion in such patients. OBJECTIVE/PATIENT: The objective of the study was to identify the molecular defect and to monitor the postnatal course of a 1-wk-old infant with elevated blood ionized calcium, serum PTH, and alkaline phosphatase and low calcium excretion. The parents were normocalcemic.

METHODS

CASR gene mutation analysis was performed on genomic DNA of the proband and her parents. The infant was treated initially with pamidronate and then cinacalcet.

RESULTS

A heterozygous mutation (R185Q, CGA > CAA) in exon 4 of the CASR gene was identified in the proband. The CASR gene of both parents was normal. At 1 wk of age, iv fluids and furosemide were initiated, but hypercalcemia, hyperparathyroidism, and low calcium excretion persisted. At 2 wk of age, a single iv dose of pamidronate resulted in hypocalcemia and further increase in PTH levels, but hypercalcemia recurred within 1 wk. At 3 wk of age, a single oral dose of cinacalcet resulted in decreased PTH levels at 2 h; blood-ionized calcium reached a nadir at 10 h. Three days later daily cinacalcet was initiated, resulting in normalization of ionized calcium. The suppression of serum PTH and reduction in total serum calcium was maintained long term.

CONCLUSIONS

In neonatal hyperparathyroidism secondary to presumed de novo heterozygous CASR mutation, treatment with cinacalcet decreases PTH secretion and serum calcium levels and mitigates the need for parathyroidectomy.

[Hyperparathyroidism: molecular, diagnostic and therapeutic aspects]

The sensitivity of parathyroid glands to a low calcium level in plasma results in parathyroid hormone (PTH) release in order to restore the normal Ca²+ concentration. Hyperparathyroidism is a common endocrinopathy, caused by uncontrolled growth of parathyroid cells. In primary hyperparathyroidism, hypercalcemia develops due to extensive autonomous secretion of PTH. Secondary hyperparathyroidism is a well-established complication of chronic renal insufficiency, where marked parathyroid hyperplasia occurs, especially in patients with long dialysis vintage. The elevated PTH level in the circulation is a direct result of renal function disturbances, vitamin D deficiency, and impaired calcium/phosphate metabolism. After successful kidney transplantation, the normalization of kidney function fails to normalize the secretion of PTH by parathyroid glands, which have become relatively autonomous and unresponsive to hypercalcemic conditions in the plasma. The development of tertiary hyperparathyroidism occurs in these conditions. The aim of our report is to present current views on the clinical, pathological and biochemical features of primary, secondary and tertiary hyperparathyroidism. The diagnostics of calcium/phosphate abnormalities in parathyroid gland disorders, as well as some aspects of hyperparathyroidism treatment, are briefly summarized.

Cinacalcet effect on severe hyperparathyroidism

To determine the efficacy and safety of cinacalcet, a calcimimetic drug that suppress parathyroid hormone (PTH) production, we studied its effect on 20 patients (13 males) on maintenance hemodialysis (HD), 80% of them have persistent high PTH levels (i.e. more than 80 pmol/L), the remaining patients had PTH levels more than 60 pmol/L. Five of 20 (25%) patients dropped out from the study (2 because of severe GIT upset, one showed severe myalgia and arthralgia, one patient due to non compliance and one died at home due to cardiac arrest). The remaining 15 patients (10 males) had a mean age of 40 ± 12.86 years and dialysis duration of 29.13 ± 18.27 months. The follow-up period on cinacalcet was 4 months with a single daily oral dose started with 30 mg/day and increased gradually according to the PTH levels. Nine (60%) patients were on concomitant active vitamin D during the study period with a mean dose of 7.33 ± 3.39 μg/week. There was a significant decrease in the serum PTH levels at the end the study compared to that at the start (46.4 ± 4.7 pmol/L versus 93.3 ± 25.6 pmol/L, respectively, P< 0.000), and the target PTH level (< 31.6 pmol/L) was achieved in 54% of patients. No significant changes in serum Ca and phosphorous levels were observed. We conclude that cinacalcet is an effective therapy to suppress the serum PTH levels and allows favorable management of the serum calcium and phosphorus levels in HD patients. The drug was well tolerated; however, GIT discomfort is a significant side effect that may necessitate drug withdrawal in some patients.

Cinacalcet decreases bone formation rate in hypercalcemic hyperparathyroidism after kidney transplantation

BACKGROUND/AIMS

Cinacalcet reduces serum calcium in kidney transplant recipients with hypercalcemic hyperparathyroidism. Its effect on bone, however, has not been investigated in this population.

METHODS

We prospectively examined bone turnover, histomorphometry and density as well as serum bone biomarkers in 10 transplant recipients before and after treatment with cinacalcet.

RESULTS

After 18-24 months of treatment with cinacalcet, bone formation decreased in 7, increased in 2, and remained zero in 1 patient (p = 0.11). Trabecular bone volume was maintained. Trabecular number decreased (p = 0.03), but trabecular thickness was unchanged (p = 0.17). Osteoid decreased (p = 0.02) and osteoblast surface increased (p = 0.02). Bone mineral density of the femur remained stable in 1 patient, decreased in 2 patients, but increased in 7 patients (p = 0.153). Serum calcium concentration (p = 0.005), iPTH (p = 0.01) and calcitonin concentration decreased (p = 0.03), while 25(OH) vitamin D(3) increased (p = 0.02). No fractures were reported. Graft function remained stable.

CONCLUSION

While cinacalcet might decrease bone formation rate, it did not change bone volume, and bone mineral density of the femur increased. Therefore, the use of cinacalcet in hypercalcemic hyperparathyroidism might be safe with regard to the bone disease present after kidney transplantation.

[Calcimimetic drugs in nondialyzed patients]

With the progression of chronic kidney disease (CKD) possibilities of regulation of parathyroid hormone (PTH) secretion also decrease. Calcimimetics offer the possibility of direct influence on pathogenic mechanisms of secondary hyperparathyroidism in the early stages of CKD. Type II calcimimetic drugs inhibit PTH secretion by sensitizing the parathyroid calcium receptor to extracellular calcium. They found clinical application of in disease states running from hyperparathyroidism. The paper discusses the application of calcimimetic drug type II--cinacalcet--in the treatment of secondary hyperparathyroidism in patients with CKD and patients with hyperparathyroidism surviving renal transplantation. Cinacalcet oral administration (15-180 mg/day) significantly reduces plasma PTH concentration (> or = 30% as compared to baseline values) at a relatively low side effects (hypocalcemia, hyperphosphatemia, gastrointestinal symptoms). In patients after renal transplantation cinacalcet, according to the majority of data, has no effect on graft function and effectively helps in the treatment of persistent hyperparathyroidism, especially running with hypercalcemia.

Cinacalcet treatment of primary hyperparathyroidism: biochemical and bone densitometric outcomes in a five-year study

CONTEXT

Primary hyperparathyroidism (PHPT) is characterized by chronically elevated serum calcium and inappropriately normal or increased PTH.

OBJECTIVE

Our objective was to evaluate long-term tolerability, safety, and efficacy of cinacalcet in PHPT patients.

DESIGN AND SETTING

A 4.5-yr open-label extension study was conducted at 14 study centers in the United States.

PATIENTS OR OTHER PARTICIPANTS

Forty-five subjects with PHPT from a double-blind, placebo-controlled, 1-yr trial were continued into this study.

INTERVENTIONS

After the parent study, all subjects were treated with 30 mg cinacalcet twice daily, increasing to 50 mg twice daily during the 12-wk titration if serum calcium levels were 10.3 mg/dl or higher and then maintained on cinacalcet for up to 4.5 yr.

MAIN OUTCOME MEASURES

Assessments included serum calcium, PTH, phosphate and alkaline phosphatase, and areal bone mineral density (aBMD). Vital signs, safety chemistries and hematology, and adverse events were monitored throughout.

RESULTS

Compared with baseline, cinacalcet treatment improved biochemical measures of PHPT including reducing serum calcium and PTH and increasing serum phosphate with slight increases in alkaline phosphatase. No changes in z-scores of aBMD at spine, hip, or wrist were seen with annual percent changes, consistent with reports for untreated postmenopausal women or PHPT patients. Safety biochemistries remained normal, and adverse events (most commonly arthralgia, myalgia, diarrhea, respiratory infection, and nausea) were mild to moderate in severity.

CONCLUSIONS

Treatment of PHPT patients with cinacalcet for up to 5.5 yr maintained normocalcemia, reduced plasma PTH, increased serum phosphate and alkaline phosphatase with no significant effects on aBMD, and was well tolerated.

Biochemical effects of calcifediol supplementation in mild, asymptomatic, hyperparathyroidism with concomitant vitamin D deficiency

It has been proposed to cautiously supplement with vitamin D to any patient with asymptomatic primary hyperparathyroidism (PHTP) and a plasma 25-hydroxyvitamin D [25(OH)D] concentration <50 nmol/l. Evidence about the safeness of this intervention is limited to two studies. Our aim was to prospectively assess the biochemical effects of one-year 25(OH)D supplementation in this context. Twenty-seven patients were included in this study. Calcifediol was started at a dose of 480-960 IU/24 h (8-16 microg/24 h) and adjusted up to a maximum of 960 IU/24 h (16 microg/24 h). Basal calcium, phosphate, albumin, total alkaline phosphatase (ALP), creatinine, 24 h calcium urinary excretion, intact PTH (iPTH) and 25(OH)D were measured before and during vitamin D supplementation. The mean basal 25(OH)D was 28.7 +/- 8.0 nmol/l, and at 12 months was 71.5 +/- 32.5 nmol/l (P = 0.00 vs. baseline). After 3, 6 and 12 months iPTH levels were 141.7 +/- 108.4 ng/l (P = 0.00 vs. baseline), 131.1 +/- 95.7 ng/l (P = 0.03 vs. baseline) and 162.2 +/- 139.3 ng/l (P = ns vs. baseline). Mean calcium did not change. Mean urinary calcium excretion increased significantly (basal: 5.7 +/- 2.9 mmol/24 h, 12 months: 7.9 +/- 4.9 mmol/24 h, P = 0.02). Cautious calcifediol supplementation significantly increased mean 25(OH)D and temporarily reduced mean iPTH. It did not change mean serum calcium, but urinary calcium excretion increased significantly. We suggest that serum calcium and 24 h calciuria be measured at regular intervals in patients with PHTP, while on calcifediol supplementation.

[The efficacy and safety of intravenous bisphosphonates in the treatment of primary hyperparathyroidism complicated by hypercalcemia crisis]

OBJECTIVE

To study the efficacy and adverse events of intravenous bisphosphonates in the treatment of patients of primary hyperparathyroidism (PHPT) complicated by hypercalcemia crisis.

METHODS

From October 2003 to December 2007, 14 patients admitted into our hospital were diagnosed as PHPT complicated by hypercalcemia crisis, which was defined as a serum calcium concentration greater than 3.50 mmol/L. Of them, 6 cases had parathyroid adenoma, 1 had hyperplasia and 7 had parathyroid carcinoma. One of the intravenous bisphosphonates including pamidronate, ibandronate and zoledronic acid was given for 29 times in all the 14 cases. Serum calcium, parathyroid hormone, hematology, and other biochemical markers were monitored. Adverse events were recorded.

RESULTS

After intravenous bisphosphonates, the serum total calcium (Ca) levels decreased from (3.85 +/- 0.50) mmol/L to (2.86 +/- 0.39) mmol/L in (1.4 +/- 0.6) days, and were kept below 3.50 mmol/L for (10.14 +/- 8.54) days. There was no significant difference of the magnitude of decrease in serum Ca levels among the patients using pamidronate, ibandronate or zoledronic acid. The change of serum Ca level was associated with the serum Ca level before treatment. The response to intravenous bisphosphonates evaluated by the decrease of serum total calcium levels was more significant in patients with parathyroid adenoma or hyperplasia than those with parathyroid carcinoma. The most common adverse event was pyrexia, which occurred 15 times (51.7%) and 75% of the pyrexia events occurred after the first infusion. Other manifestations included fatigue, flu-like symptom, myalgia, arthralgia and diarrhea with an incidence of 3.4% each (one event in the 29 times of treatment). There were 2 events (6.7%) with mild increase of serum creatinine concentration.

CONCLUSION

Bisphosphonates can decrease serum total calcium levels in hypercalcemia crisis caused by PHPT effectively with mild adverse events.

Influence of somatostatin to biochemical parameters in patients with primary hyperparathyroidism

Somatostatin (SRIF) is effective in the nonoperative management of a variety endocrine tumors. A potential role of SRIF for treatment of patients with primary hyperparathyroidism (pHPT) has been suggested. In a controlled, prospective, triple-blinded, randomized clinical trial, the somatostatin analogue octreotide (SMS 201-995, Sandostatin) was evaluated in 40 patients with well documented pHPT. Amongst other biochemical parameters, serum calcium and-phosphate and levels of parathyroid hormone, calcitonin, and osteocalcin as well as octreotide were assessed before and for 4 hours after a single iv. application of 200 micrograms ocreotide or placebo. SRIF-receptor autoradiography was performed in parathyroid tissue samples. Baseline values revealed a constellation of biochemical parameters typically found in pHPT. Following 200 micrograms octreotide, no significant changes in any of the biochemical parameters investigated for were observed. Multivariate analysis was performed to identify patient subpopulations in which any given combination of laboratory parameters changed in response to either drug or placebo. However, no 'responders' to octreotide were identified. 45% of patients receiving octreotide, reported side effects. Parathyroid tissue samples were negative for SRIF-receptor expression. It is concluded that a single dose iv. application of octreotide does not result in appreciable changes of biochemical parameters relevant in pHPT and carries a high rate of side effects. Furthermore, absence of SRIF-receptors in parathyroid tissue from patients with pHPT, together with lack of octreotide effects, suggests that somatostatin-analogues may not be effective in the non-operative therapy of pHPT.

Dissociation between changes in immunoreactive parathormone and its biological indices induced by cimetidine in primary hyperparathyroidism

In three out of four patients with primary hyperparathyroidism, 2 000 mg of cimetidine daily caused a reduction of immunoreactive parathormone (iPTH) when measured at 8.30 and 11.30 on days 16 and 17 on treatment. Serum Ca, PO4 and maximal tubular reabsorption of PO4 remained unchanged. Excretion of cAMP/100 ml GFR remained elevated to at least the same extent as before treatment. Two patients, in whom cimetidine treatment was continued for an additional 4 weeks, did not show further hormonal or biochemical changes compared with the evaluation on days 16 and 17. We conclude that reduction of iPTH is not accompanied by any change in biological activity of this hormone. The reason for this discrepancy remains unclear.