Cinacalcet treatment of primary hyperparathyroidism

Glycolate oxidase-1 gene variants influence the risk of hyperoxaluria and renal stone development

PURPOSE

Oxalate is an excellent calcium ion attractor with great abundance in the human body, and the liver is the major source of oxalate. The Glycolate oxidase-1 (GOX1) gene is solely responsible for the glycolate and glyoxylate metabolism and produces oxalate. This study has been designed to comprehend the association of genetic variants of the GOX1 gene with the risk of hyperoxaluria and renal stone disease in the Indian population.

METHOD

The present study is a candidate gene approach prospective case-control study carried out on 300 participants (150 cases and 150 controls) at Muljibhai Patel Urological Hospital, Gujarat, India. Biochemical parameters, including serum levels of calcium, creatinine, parathyroid hormone, and 24-h urine metabolites, were performed. The genotyping of GOX1 gene variants rs6086287, rs2235250, rs2255183, and rs2294303 was performed using a customized TaqMan assay probe by RT-PCR.

RESULT

Parathyroid hormone, serum creatinine, and urine metabolites were significantly elevated in nephrolithiasis compared to healthy individuals. All mutated homozygous genotypes GG (rs6086287), TT (rs2235250), GG (rs2255183), and CC (rs2294303) were significantly associated with a high risk of renal stone disease. Individuals diagnosed with hyperoxaluria and carrying TG (rs6086287), AG (rs2255183), and TT (rs2294303) genotypes have a significantly high risk of renal stone disease. Moreover, haplotype analysis and correlation analysis also confirmed the strong association between genetic variants and nephrolithiasis.

CONCLUSION

Genetic variants of the GOX1 genes were associated with renal stone disease. In the presence of risk genotype and hyperoxaluria, the susceptibility to develop renal stone disease risk gets modulated.

Subtotal Parathyroidectomy Successfully Controls Calcium Levels of Patients with Neonatal Severe Hyperparathyroidism Carrying a Novel CASR Mutation

INTRODUCTION

Inactivating mutations of the calcium-sensing receptor (CASR) gene result in neonatal severe hyperparathyroidism (NSHPT). Total parathyroidectomy is an effective way to control life-threatening hypercalcemia in NSHPT but leads to permanent hypoparathyroidism. An alternative surgical option is subtotal parathyroidectomy. However, few cases were reported in the literature. Here, we report two unrelated NSHPT patients, one with a novel homozygous mutation (c.1817T>C; p.Leu606Pro) in CASRand the other with heterozygous for the same mutation who also carried two rare intronic variants in CASR. The outcomes of subtotal parathyroidectomy in these patients are also described.

CASE PRESENTATION

Two infants presented with an alteration of consciousness, respiratory distress, and bradycardia. Severe hypercalcemia, hypophosphatemia, and markedly elevated parathyroid hormone levels were identified, suggesting NSHPT. Cinacalcet was unable to control calcium (Ca) levels of both patients. A novel heterozygous and homozygous missense mutation c.1817T>C; p.Leu606Pro was identified in patients 1 and 2, respectively. Based on the model prediction, proline substitution at Leu606 is likely to disrupt conversion between the active and inactive conformations at the extracellular to transmembrane domain interface of CASR. In addition, two extremely rare intronic variants in CASR (chr3:g.122180314A>G and chr3:g.122251601G>A, based on GRCh38) were identified in patient 1 and his mother. These variants might have contributed to the clinical manifestations of patient 1 who was heterozygous for the c.1817T>C; p.Leu606Pro variant. Subtotal parathyroidectomy was performed by removing three and a half parathyroid glands. So far, patient 1 has been in normocalcemia for 5 years. Patient 2 was in normocalcemia for 16 months after surgery and subsequently developed mild hypoparathyroidism which required only low-dose calcitriol treatment.

CONCLUSION

We report a novel heterozygous and homozygous missense variant (c.1817T>C; p.Leu606Pro) in CASR in two NSHPT patients. The mutation likely disrupts conformational changes of CASR and results in cinacalcet unresponsiveness. Intronic variants in CASR identified in the patient with heterozygous variant might have contributed to the clinical manifestations of the patient. Although total parathyroidectomy is widely accepted as a standard treatment for NSHPT, we demonstrate that subtotal parathyroidectomy is also an effective procedure to normalize Ca levels and allow these patients to be in normocalcemia or mild hypoparathyroidism, which is simply controlled by low-dose calcitriol treatment. Subtotal parathyroidectomy appeared to be an effective treatment for NSHPT regardless of the molecular etiologies.

Haplotype of CaSR gene is associated with risk of renal stone disease in West Indian population

Calcium is the most abundant metabolite involved in the stone matrix. The CaSR gene controls calcium homeostasis, and genetic variation in the CaSR gene could lead to the development of renal stone disease. Therefore, the current study has been designed to assess the association of genetic variants of CaSR gene polymorphisms with renal stone disease. A single-centric prospective study has been carried out on a total of 300 participants (150 cases and 150 controls). Serum levels of calcium, creatinine, parathyroid hormone, and 24 h urine metabolites were measured. Two polymorphisms, rs1801725 and rs1042636, of the CaSR gene, have been genotyped for each participant. T test, binary logistic regression, and Chi-square analysis were used for statistical analysis. Renal stone patients had significantly higher levels of serum parathyroid hormone, creatinine, and 24-h urine metabolites in comparison to the controls. CaSR gene variants, rs1801725 (GG) and rs1042636 (AA), both have shown significant association with renal stone disease. In addition, individuals having specific genotypes along with metabolic abnormalities such as hypercalcemia and hyperparathyroidism are found to be at a higher significant risk of developing the renal stone disease. In the present study, the haplotype of the CaSR gene has shown an association with renal stone disease. Individuals with hyperparathyroidism and hypercalcemia and risk genotype have a higher susceptibility to developing renal stone disease.

Medical management of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is an endocrine disorder resulting from the hyperfunction of one or more parathyroid glands, with hypersecretion of parathyroid hormone (PTH). It can be managed by parathyroidectomy (PTX) or non-surgically. Medical therapy with pharmacological agents is an alternative for those patients with asymptomatic PHPT who meet guidelines for surgery but are unable or unwilling to undergo PTX. In this review, we focus upon these non-surgical aspects of PHPT management. We emphasize the most studied and widely used pharmacological alternatives: bisphosphonates, denosumab, cinacalcet and hormone therapy, in addition to combined therapy. We also address the relevant aspects of perioperative management.

Sporadic Primary Hyperparathyroidism

Sporadic primary hyperparathyroidism is a common endocrinopathy, particularly afflicting postmenopausal women and both African American men and women. Although classic signs and symptoms of the disease are well appreciated and described, because of the ease and availability and low threshold for screening, the disorder often is diagnosed in patients who are minimally symptomatic or asymptomatic. Surgery conducted by experienced endocrine surgeons has a high cure rate, particularly if guided by concordant imaging. In patients who cannot safely undergo surgery or who fail to be cured, medical therapy with the oral calcimimetic cinacalcet is a validated option for controlling serum calcium levels.

Radiofrequency Ablation of Parathyroid Adenomas: Safety and Efficacy in a Study of 10 Patients

PURPOSE

To evaluate safety and effectiveness of ultrasound-guided percutaneous radiofrequency ablation of parathyroid adenoma in surgically unfit patients with hypercalcemia because of hyperparathyroidism.

MATERIALS AND METHODS

A retrospective review of hospital records from Jan 2012 to Dec 2018 revealed 10 patients, who had undergone ablation for solitary parathyroid adenoma. All 10 patients suffered from hyperparathyroidism because of parathyroid adenoma, resulting in hypercalcemia. These patients were surgically unfit because of comorbidities. Pre-ablation serum calcium and serum parathormone levels were measured and compared with the levels after the ablation.

RESULTS

Mean serum calcium level decreased significantly from 2.81 ± 0.17 mmol/L pre-ablation to 2.42 ± 0.17 mmol/L 72 h after ablation and parathyroid hormone levels became normal in all patients within 7 days. Seven patients remained normo-calcaemic at 6 months follow-up with no signs and symptoms of hyperparathyroidism. One patient with pancreatitis died after 15 days because of pre-existing multi-organ failure. Two patients were lost to follow-up before 6 months.

CONCLUSION

Radiofrequency ablation of parathyroid adenoma is a safe and effective alternate treatment method for symptomatic hypercalcemia in surgically unfit patients suffering from primary hyperparathyroidism because of parathyroid adenoma.

Mental Effects of Excess Parathyroid Hormone in Hemodialysis Patients: A Possible Role for Parathyroid 2 Hormone Receptor?

Depression as measured by the kidney disease quality of life (KDQOL) form is known to be an independent risk factor for mortality dialysis patients. Excess parathyroid hormone (PTH) has long been associated with neuropsychiatric disturbances. Those psychiatric complications are currently attributed to hypercalcemia with very little evidence; however, with the discovery of the parathyroid hormone 2 receptor (PTH2R) in the brain which can be activated by PTH, PTH2R might indicate a direct effect of PTH. As secondary and tertiary hyperparathyroidism is common in dialysis patients where the serum calcium is low or normal, we chose to investigate a possible relationship between PTH levels and depression in dialysis patients. This was a matched pair observational study with 10 patients with intact PTH values above 1000 pg/mL who were matched with 10 patients who had PTH values less than 400 pg/mL for the presence of diabetes, years on dialysis, duration of dialysis time, Kt/V, hemoglobin, and 25 OH vitamin D levels, as well as intravenous iron and erythropoietin administration. The Kidney Disease Quality of Life questionnaire (KDQOL-36) scores and patient Health Questionnaire scores were analyzed during that time. All variables underwent tests for normality and matched pair t-test. All subscales of the KDQOL-36 were worse in the high PTH group with the effect on daily life reaching P = 0.01 and the burden of disease and symptoms both reaching P = 0.02. PTH and PTH2R may be appropriate targets for investigations to improve the quality of life in hemodialysis patients.

Calcium-sensing receptor in colorectal inflammation and cancer: Current insights and future perspectives

The extracellular calcium-sensing receptor (CaSR) is best known for its action in the parathyroid gland and kidneys where it controls body calcium homeostasis. However, the CaSR has different roles in the gastrointestinal tract, where it is ubiquitously expressed. In the colon, the CaSR is involved in controlling multiple mechanisms, including fluid transport, inflammation, cell proliferation and differentiation. Although the expression pattern and functions of the CaSR in the colonic microenvironment are far from being completely understood, evidence has been accumulating that the CaSR might play a protective role against both colonic inflammation and colorectal cancer. For example, CaSR agonists such as dipeptides have been suggested to reduce colonic inflammation, while dietary calcium was shown to reduce the risk of colorectal cancer. CaSR expression is lost in colonic malignancies, indicating that the CaSR is a biomarker for colonic cancer progression. This dual anti-inflammatory and anti-tumourigenic role of the CaSR makes it especially interesting in colitis-associated colorectal cancer. In this review, we describe the clinical and experimental evidence for the role of the CaSR in colonic inflammation and colorectal cancer, the intracellular signalling pathways which are putatively involved in these actions, and the possibilities to exploit these actions of the CaSR for future therapies of colonic inflammation and cancer.

Diagnosis, management, histology and genetics of sporadic primary hyperparathyroidism: old knowledge with new tricks

Primary hyperparathyroidism (pHPT) is a common endocrinopathy resulting from inappropriately high PTH secretion. It usually results from the presence of a single gland adenoma, multiple gland hyperplasia or rarely parathyroid carcinoma. All these conditions require different management, and it is important to be able to differentiate the underlined pathology, in order for the clinicians to provide the best therapeutic approach. Elucidation of the genetic background of each of these clinical entities would be of great interest. However, the molecular factors that control parathyroid tumorigenesis are poorly understood. There are data implicating the existence of specific genetic pathways involved in the emergence of parathyroid tumorigenesis. The main focus of the present study is to present the current optimal diagnostic and management protocols for pHPT as well as to review the literature regarding all molecular and genetic pathways that are to be involved in the pathophysiology of sporadic pHPT.

Hyperparathyroidism-jaw Tumor Syndrome: An Overlooked Cause of Severe Hypercalcemia

Ossifying fibromas of the maxillofacial bones are an uncommon form of benign neoplasm usually treated by surgical excision. Up to 30% of patients with hyperparathyroidism-jaw tumor syndrome, a rare form of multiple endocrine neoplasia resulting from autosomal dominant inactivating mutation of the Hrpt2 tumor suppressor gene, initially present with ossifying fibromas. Coincident hypercalcemia because of the presence of parathyroid adenoma is common in these patients, of whom 15% may have or may develop parathyroid carcinoma. The authors present a case of severe postsurgical hypercalcemia after removal of a large maxillary ossifying fibroma in a patient with previously unrecognized hyperparathyroidism-jaw tumor AU3 syndrome.

Intraoperative Parathyroid Hormone Monitoring: Optimal Utilization

Intraoperative parathyroid hormone (IOPTH) monitoring is a highly accurate surgical adjunct used to determine the extent of surgery in the setting of primary hyperparathyroidism. It is the successful interpretation of changes in PTH levels that is essential for using this technique in a way to optimize cure. Thus, it is imperative that the surgeon has an understanding of PTH dynamics and carefully chooses the appropriate IOPTH protocol and interpretation criteria that will best predict operative success, minimize unnecessary bilateral exploration, decrease the likelihood of resecting parathyroid glands that are not hypersecreting, and prevent recurrence.

Experience with cinacalcet in primary hyperparathyroidism: results after 1 year of treatment

OBJECTIVES

To assess the characteristics of patients with primary hyperparathyroidism (PHPT) treated with cinacalcet and to evaluate its efficacy in reducing serum calcium and parathyroid hormone (PTH) concentrations after 1 year of treatment.

METHODS

The study included 20 patients with PHPT who had completed at least 12 months of treatment with cinacalcet (eight patients for refusal of parathyroidectomy, three for surgery not possible due to comorbidities and nine for progressive hypercalcemia prior to surgery). We recorded clinical and biochemical data at baseline, and after 3, 6 and 12 months of treatment. We also monitored adverse events. Cinacalcet was administered in increasing doses until normal serum calcium was reached or side effects preventing a further increase occurred.

RESULTS

After 3 months of treatment, serum calcium significantly decreased (11.73 ± 0.85 versus 10.71 ± 1.63 mg/dl, p < 0.001) and serum phosphorus significantly increased (2.41 ± 0.48 versus 2.63 ± 0.70 mg/dl, p = 0.004) while no significant change occurred in PTH (181.91 ± 102.37 versus 195.47 ± 111.71 pg/ml, p = 0.695). No further variation was observed after 6 months compared with 3 months of follow up. However, after 12 months of treatment, there was a significant decrease in PTH concentrations compared with baseline (181.91 ± 102.37 versus 152.47± 70.16 pg/ml, p = 0.028) as well as serum calcium (11.73 ± 0.85 versus 10.20± 0.95 mg/dl, p < 0.001); serum phosphorus significantly increased (2.41 ± 0.48 versus 2.71 ± 0.43 mg/dl, p = 0.01). Normocalcemia (S-Ca < 10.2 mg/dl) was achieved in 55% of patients. The medication was usually well tolerated (83.4%). Most common adverse events were nausea and vomiting, especially at the beginning of therapy.

CONCLUSION

Cinacalcet rapidly reduced serum calcium in patients with PHPT and this reduction remained stable after 1 year of treatment. We also observed a decrease in PTH. Cinacalcet is an effective alternative in nonsurgical treatment of PHPT and may be useful in the preoperative hypercalcemia management.

Superiority of minimally invasive parathyroidectomy

Because greater than 80% of spontaneous cases of primary hyperparathyroidism are caused by a single adenoma, BCE of the neck, which has long been the approach of choice, is being replaced. Focused parathyroidectomy has been made possible by advances in preoperative parathyroid localization and IOPTH monitoring, which allows confirmation of cure and confirmation of the absence of MGD without visualizing all 4 parathyroids. Several techniques for focused parathyroidectomy exist, but open MIP through an incision of 2 to 3 cm with surgeon-administered locoregional anesthesia seems to improve on the already high success rate and low morbidity associated withimproe on bilateral exploration. In addition, MIP is associated with numerous secondary benefits such as decreased hospital cost, improved patient satisfaction, decreased operative time, and same-day discharge. Bilateral exploration will remain the standard of care for most patients with multigland or syndromic disease. Most patients with sporadic PHPT are candidates for MIP.

Association of parathyroid hormone and 25-OH-vitamin D levels with arterial stiffness in postmenopausal women with vitamin D insufficiency

AIM

Vitamin D insufficiency and increased parathyroid hormone (PTH) levels have been suggested as prognostic indices for cardiovascular disease. Arterial stiffness, a surrogate marker for cardiovascular disease, is often increased in patients with primary hyperparathyroidism. PTH levels increase in patients with low 25-OH-vitamin D levels, but the influence of such an increase on arterial stiffness has not been investigated in postmenopausal women with reduced 25-OH-vitamin D levels. We therefore investigated the association between PTH and aortic stiffness in postmenopausal women with reduced 25-OH-vitamin D levels.

METHODS

One hundred fifty postmenopausal women with 25-OH-vitamin D insufficiency (<30 ng/mL) were recruited. Aortic pulse wave velocity (aPWV), a measure of arterial stiffness, PTH and 25-OH-vitamin D levels were measured. Cardiovascular risk factors and markers of bone formation were evaluated.

RESULTS

The 25-OH-vitamin D levels were associated with aPWV (rho=-0.23, p=0.006), but the association was not significant when controlling for PTH. Significant correlates of aPWV included age, body mass index, mean arterial pressure and PTH (rho=0.39, p<0.001). Arterial stiffness was predicted by logarithmically transformed PTH levels (β=0.23, p=0.007), independent of traditional cardiovascular risk factors and factors involved in bone formation. Increased PTH levels (>62 pg/mL) were associated with a 3.0-5.4-fold increased probability of having a mild-severe increase in aortic stiffness, irrespective of confounders.

CONCLUSION

Among postmenopausal women with reduced 25-OH-vitamin D levels, elevated PTH levels were a significant predictor of aortic stiffness, irrespective of cardiovascular risk factors and of factors involved in bone formation. PTH accounted for the association between 25-OH-vitamin D levels and aortic stiffness.