Muscle function and quality of life are not impaired in familial hypocalciuric hypercalcemia: a cross-sectional study on physiological effects of inactivating variants in the calcium-sensing receptor gene (CASR)

Double jeopardy: a patient's tale of two concurrent hypercalcaemic syndromes

Primary hyperparathyroidism (PHPT) is the most common cause of parathyroid hormone (PTH) dependent hypercalcaemia, however there are few reported cases of its co-occurrence in patients with familial hypocalciuric hypercalcaemia (FHH). This case highlights the challenges in managing a rare case of dual pathology. A 49-year-old Caucasian woman with symptoms of hypercalcaemia presented with an adjusted serum calcium of 2.77 mmol/L and PTH of 11.5 pmol/L. Neck ultrasound and sestamibi scan were concordant with a left lower parathyroid adenoma, and a preoperative dual-energy X-ray absorptiometry scan confirmed osteopenia. Parathyroidectomy resulted in a PTH reduction from 11.5 pmol/L to 2.7 pmol/L. Interestingly, her lowest pre-operative adjusted serum calcium of 2.67 mmol/L remained unchanged 14 months post-parathyroidectomy. Twenty-four hours urine calcium:creatinine clearance ratio performed postoperatively was low and sequencing analysis of the calcium-sensing receptor gene confirmed the coexistence of FHH. Although surgery is not indicated in FHH, parathyroidectomy may help reduce hypercalcaemia and its associated complications if there is coexistent PHPT.

Effects of Supplemental Vitamin D on Muscle Performance and Quality of Life in Graves' Disease: A Randomized Clinical Trial

Background: Vitamin D deficiency has been proposed to have a role in the development and course of Graves' disease (GD). Muscle weakness and quality of life (QoL) impairments are shared features of GD and vitamin D deficiency. We aimed at investigating whether vitamin D supplementation would improve restoration of muscle performance and thyroid-related QoL in GD and at describing the effect of anti-thyroid medication (ATD) on these outcomes. Methods: In a double-blinded clinical trial, hyperthyroid patients with a first-time diagnosis of GD were randomized to vitamin D 70 μg (2800 IU)/day or matching placebo as add-on to standard ATD. At baseline and after 3 and 9 months of intervention, we assessed isometric muscle strength, muscle function tests, postural stability, body composition, and QoL-impairment by using the ThyPRO questionnaire. Linear mixed modeling was used to analyze between-group differences. (The DAGMAR study clinicaltrials.gov ID NCT02384668). Results: Nine months of vitamin D supplementation caused an attenuation of muscle strength increment in all muscle measures investigated, significant at knee extension 60° where the increase was 24% lower (p = 0.04) in the vitamin D group compared with placebo. Compared with placebo, vitamin D supplementation tended to reduce gain of lean body mass (-24%, p = 0.08). Vitamin D supplementation significantly impeded alleviation of Composite QoL and the same trend was observed for the Overall QoL-Impact and Impaired Daily Life scales. In response to ATD, all measures improved significantly. The increase in muscle strength ranged from 25% to 40% (p_all < 0.001), and increment of lean body mass was 10% (p < 0.001). Large changes were observed in all QoL scales. Conclusions: Nine months of vitamin D supplementation caused unfavorable effects on restoration of muscle performance. In contrast, ATD treatment was associated with marked improvement in all measures of muscle performance and thyroid-related QoL. In patients with newly diagnosed GD, high-dose vitamin D supplementation should not be recommended to improve muscle function, but ATD is of major importance to alleviate muscle impairment.

Familial Hypocalciuric Hypercalcemia in Pregnancy: Diagnostic Pitfalls

Familial hypocalciuric hypercalcemia (FHH) is a group of autosomal dominant disorders caused by dysfunction of the calcium sensing receptor (CaSR) and its downstream signaling proteins, leading to generally asymptomatic hypercalcemia. During pregnancy, distinguishing FHH from primary hyperparathyroidism (PHPT) is important, as the latter is associated with adverse outcomes and can be treated surgically during pregnancy, whereas the former is benign. This case report highlights the difficulties in diagnosing FHH during pregnancy. A 32‐year‐old woman was found to have asymptomatic hypercalcemia at 14‐weeks’ gestation. Investigations showed a corrected calcium (cCa) of 2.61 mmol/L (2.10 to 2.60), ionized Ca (iCa) of 1.40 mmol/L (1.15 to 1.28), 25OHD of 33 nmol/L (75 to 250), and PTH of 9.5 pmol/L (1.5 to 7.0). The patient was treated with 2000 IU cholecalciferol daily with normalization of 25OHD. The urine calcium / creatinine clearance ratio (CCCR) was 0.0071, and neck US did not visualize a parathyroid adenoma. Upon a retrospective review of the patient's biochemistry from 2 years prior, hypercalcemia was found that was not investigated. The patient was monitored with serial iCa levels and obstetric US. She delivered a healthy boy at 38‐weeks’ gestation. Postnatal iCa was 1.48 mmol/L and remained elevated. Her son had elevated iCa at birth of 1.46 mmol/L (1.15 to 1.33), which rose to 1.81 mmol/L by 2 weeks. He was otherwise well. Given the familial hypercalcemia, a likely diagnosis of FHH was made. Genetic testing of the son revealed a missense mutation, NM_000388.3(CASR):c.2446A > G, in exon 7 of the CaSR, consistent with FHH type 1. To our knowledge, there are only three existing reports of FHH in pregnancy. When differentiating between FHH and PHPT in pregnancy, interpretation of biochemistry requires an understanding of changes in Ca physiology, and urine CCCR may be unreliable. If the decision is made to observe, clinical symptoms, calcium levels, and fetal US should be monitored, with biochemistry and urine CCCR performed postpartum, once lactation is completed © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Muscle Performance and Postural Stability Are Reduced in Patients with Newly Diagnosed Graves' Disease

Background: Reduced muscle strength is an acknowledged symptom of Graves' disease, but the knowledge on severity is sparse. This study aimed to investigate muscle strength, balance, and muscle function in patients with Graves' disease compared to age- and sex-matched healthy controls. Methods: Using a cross-sectional design, 55 patients newly diagnosed with Graves' disease were compared to 55 euthyroid controls, matched on sex, age, and menopausal status. Isometric muscle strength (N) and maximum force production (N/s) were measured across different muscles groups using a dynamometer chair and postural stability (balance) in different positions using a stadiometer. Muscle function was assessed using the Timed-Up-and-Go test and the Repeated Chair Stand test. Results: Patients and controls were well matched. Handgrip maximum muscle strength as well as strength at elbow and knee flexion and extension were significantly impaired in patients compared to controls. Maximum force production was only significantly reduced at elbow flexion. Patients performed the Timed-Up-and-Go and the Repeated Chair Stand test significantly slower than controls, and postural stability was significantly reduced in patients compared to controls in all positions. Free triiodothyronine correlated with reduced muscle strength and postural stability. Conclusions: At the time of diagnosis, Graves' disease is associated with impaired maximum muscle strength, performance, and balance, whereas maximum force production is overall comparable to euthyroid controls.

Pro-FHH: A Risk Equation to Facilitate the Diagnosis of Parathyroid-Related Hypercalcemia

CONTEXT

Parathyroid-related hypercalcemia is due to primary hyperparathyroidism (PHPT) or to familial hypocalciuric hypercalcemia (FHH). PHPT can lead to complications that necessitate parathyroidectomy. FHH is a rare genetic disease resembling PHPT; surgery is ineffective. A reliable method for distinguishing FHH from PHPT is needed.

OBJECTIVE

To develop an easy-to-use tool to predict if a patient has PHPT.

DESIGN

Retrospective analysis of two prospective cohorts. Development of an unsupervised risk equation (Pro-FHH).

SETTING

University hospitals in Paris, France, and Aarhus, Denmark.

PARTICIPANTS

Patients (Paris: 65 with FHH, 85 with PHPT; Aarhus: 38 with FHH, 55 with PHPT) were adults with hypercalcemia and PTH concentration within normal range.

MAIN OUTCOME MEASURES

Performance of Pro-FHH to predict PHPT.

RESULTS

Pro-FHH takes into account plasma calcium, PTH, and serum osteocalcin concentrations, and calcium-to-creatinine clearance ratio calculated from 24-hour urine collection (24h-CCCR). In the Paris cohort, area under the receiver operating characteristic curve (AUROC) of Pro-FHH was 0.961, higher than that of 24h-CCCR. With a cutoff value of 0.928, Pro-FHH had 100% specificity and 100% positive predictive value for the diagnosis of PHPT; it correctly categorized 51 of 85 patients with PHPT; the remaining 34 were recommended to undergo genetic testing. No patients with FHH were wrongly categorized. In an independent cohort from Aarhus, AUROC of Pro-FHH was 0.951, higher than that of 24h-CCCR.

CONCLUSION

Pro-FHH effectively predicted whether a patient has PHPT. A prospective trial is necessary to assess its usefulness in a larger population and in patients with elevated PTH concentration.

AP2S1 and GNA11 mutations - not a common cause of familial hypocalciuric hypercalcemia

OBJECTIVE

Familial hypocalciuric hypercalcemia (FHH) type 1 is caused by mutations in the gene encoding the calcium-sensing receptor (CASR). Recently, mutations affecting codon 15 in the gene AP2S1 have been shown to cause FHH type 3 in up to 26% of CASR-negative FHH patients. Similarly, mutations in the gene GNA11 have been shown to cause FHH type 2. We hypothesized that mutations in AP2S1 and GNA11 are causative in Danish patients with suspected FHH and that these mutations are not found in patients with primary hyperparathyroidism (PHPT), which is the main differential diagnostic disorder.

DESIGN

Cross-sectional study.

METHODS

We identified patients with unexplained hyperparathyroid hypercalcemia and a control group of verified PHPT patients through review of 421 patients tested for CASR mutations in the period 2006-2014. DNA sequencing of all amino acid coding exons including intron-exon boundaries in AP2S1 and GNA11 was performed.

RESULTS

In 33 CASR-negative patients with suspected FHH, we found two (~6%) with a mutation in AP2S1 (p.Arg15Leu and p.Arg15His). Family screening confirmed the genotype-phenotype correlations. We did not identify any pathogenic mutations in GNA11. No pathogenic mutations were found in the PHPT control group.

CONCLUSIONS

We suggest that the best diagnostic approach to hyperparathyroid hypercalcemic patients suspected to have FHH is to screen the CASR and AP2S1 codon 15 for mutations. If the results are negative and there is still suspicion of an inherited condition (i.e. family history), then GNA11 should be examined.

Association between bone indices assessed by DXA, HR-pQCT and QCT scans in post-menopausal women

Quantitative computed tomography (QCT), high-resolution peripheral QCT (HR-pQCT) and dual X-ray absorptiometry (DXA) scans are commonly used when assessing bone mass and structure in patients with osteoporosis. Depending on the imaging technique and measuring site, different information on bone quality is obtained. How well these techniques correlate when assessing central as well as distal skeletal sites has not been carefully assessed to date. One hundred and twenty-five post-menopausal women aged 56-82 (mean 63) years were studied using DXA scans (spine, hip, whole body and forearm), including trabecular bone score (TBS), QCT scans (spine and hip) and HR-pQCT scans (distal radius and tibia). Central site measurements of areal bone mineral density (aBMD) by DXA and volumetric BMD (vBMD) by QCT correlated significantly at the hip (r = 0.74, p < 0.01). Distal site measurements of density at the radius as assessed by DXA and HR-pQCT were also associated (r = 0.74, p < 0.01). Correlations between distal and central site measurements of the hip and of the tibia and radius showed weak to moderate correlation between vBMD by HR-pQCT and QCT (r = -0.27 to 0.54). TBS correlated with QCT at the lumbar spine (r = 0.35) and to trabecular indices of HR-pQCT at the radius and tibia (r = -0.16 to 0.31, p < 0.01). There was moderate to strong agreement between measuring techniques when assessing the same skeletal site. However, when assessing correlations between central and distal sites, the associations were only weak to moderate. Our data suggest that the various techniques measure different characteristics of the bone, and may therefore be used in addition to rather than as a replacment for imaging in clinical practice.

The cardiovascular system in familial hypocalciuric hypercalcemia: a cross-sectional study on physiological effects of inactivating variants in the calcium-sensing receptor gene

OBJECTIVE

Loss-of-function variants in the gene encoding the calcium-sensing receptor (CASR) result in familial hypocalciuric hypercalcemia (FHH), causing hypercalcemia with high normal or elevated parathyroid hormone levels. The CASR may also influence electrolyte and water homeostasis. It is unknown whether FHH affects cardiovascular health. We, therefore investigated whether FHH is associated with changes in the regulation of the cardiovascular system by measuring 24-h blood pressure (BP), arterial stiffness and vasoactive hormones.

DESIGN

Cross-sectional study comparing 50 patients with FHH to age- and gender-matched controls.

RESULTS

Studied subjects (69% women) had a mean age of 56years. A similar number of patients and controls (33%) were on treatment with antihypertensive drugs. Overall, no differences were found between groups in 24-h ambulatory BP or pulse wave velocity. However, compared with controls, diastolic BP during nighttime was lower in FHH females (60±5 vs 66±9mmHg, P<0.01) and higher in FHH males (69±6 vs 64±5mmHg, P=0.02). FHH was associated with a significantly higher plasma osmolality (P<0.01), higher plasma levels of vasopressin (P<0.01) and a higher renal excretion of epithelial sodium channels (ENaCs) (P=0.03), whereas urine aquaporin-2 and plasma sodium, aldosterone and renin did not differ between groups. FHH patients had a lower urinary volume with an increased osmolality if analyses were restricted to those not on treatments with antihypertensive drugs.

CONCLUSIONS

FHH does not seem to be associated with an increased risk of CVD.

Multiple endocrine neoplasia phenocopy revealed as a co-occurring neuroendocrine tumor and familial hypocalciuric hypercalcemia type 3

Familial hypocalciuric hypercalcemia type 3 should be considered as differential diagnosis in patients with suspected primary hyperparathyroidism and/or suspected multiple neoplasia syndrome, as correct diagnosis will spare the patients for going through multiple futile parathyroidectomies and for the worry of being diagnosed with a cancer susceptibility syndrome.

Inverse Correlation at the Hip Between Areal Bone Mineral Density Measured by Dual-Energy X-ray Absorptiometry and Cortical Volumetric Bone Mineral Density Measured by Quantitative Computed Tomography

Quantitative computed tomography (QCT) is considered to measure true volumetric bone mineral density (vBMD; mg/cm3) and enables differentiation between cortical and trabecular bone. We aimed to determine the value of QCT by correlating areal BMD (aBMD) by dual-energy X-ray absorptiometry (DXA) with vBMD when using a fixed threshold to delineate cortical from trabecular bone. In a cross-sectional study, 98 postmenopausal women had their hip scanned by DXA and by QCT. At the total hip and the trabecular bone compartment, aBMD correlated significantly with vBMD (r=0.74 and r=0.63; p<0.01, respectively). A significant inverse correlation was found between aBMD and cortical vBMD (r=-0.57; p<0.01). Total hip volume by QCT did not change with aBMD. However, increased aBMD was associated with a decreased trabecular bone volume (r=-0.36; p<0.01) and an increased cortical volume (r=0.69; p<0.01). Changing the threshold used to delineate cortical from trabecular bone from default 350 mg/cm3 to either 300 or 400 mg/cm3 did not affect integral vBMD (p=89) but had marked effects on estimated vBMD at the cortical (p<0.001) and trabecular compartments (p<0.001). Furthermore, increasing the threshold decreased cortical thickness (p<0.001), whereas the strength parameter in terms of buckling ratio increased (p<0.001). Our results show good agreement between aBMD and integral vBMD. However, using a fixed threshold to differentiate cortical from trabecular bone causes an apparent increase in cortical volume with a decrease in cortical density as aBMD increases. This may be caused by the classification of a larger part of the transition zone as cortical bone with increased aBMD.

No beneficial effects of vitamin D supplementation on muscle function or quality of life in primary hyperparathyroidism: results from a randomized controlled trial

CONTEXT

Impairments of muscle function and strength in patients with primary hyperparathyroidism (PHPT) are rarely addressed, although decreased muscle function may contribute to increased fracture risk.

OBJECTIVE

We aimed to assess the changes in muscle strength, muscle function, postural stability, quality of life (QoL), and well-being during treatment with vitamin D or placebo before and after parathyroidectomy (PTX) in PHPT patients.

DESIGN

A randomized placebo-controlled trial.

PATIENTS

We included 46 PHPT patients, mean age 58 (range 29-77) years and 35 (76%) were women.

INTERVENTIONS

Daily treatment with 70 μg (2800 IU) cholecalciferol or placebo for 52 weeks. Treatment was administered 26 weeks before PTX and continued for 26 weeks after PTX.

MAIN OUTCOME MEASURES

Changes in QoL and measures of muscle strength and function.

RESULTS

Preoperatively, 25-hydroxyvitamin D (25OHD) increased significantly (50-94 nmol/l) compared with placebo (57-52 nmol/l). We did not measure any beneficial effects of supplementation with vitamin D compared with placebo regarding well-being, QoL, postural stability, muscle strength, or function. In all patients, we measured marked improvements in QoL, well-being (P<0.01), muscle strength in the knee flexion and extension (P<0.001), and muscle function tests (P<0.01) after surgical cure. Postural stability improved during standing with eyes closed (P<0.05), but decreased with eyes open (P<0.05).

CONCLUSIONS

Patients with PHPT and 25OHD levels around 50 nmol/l did not benefit from vitamin D supplementation concerning muscle strength, muscle function, postural stability, well-being, or QoL. Independent of preoperative 25OHD levels, PTX improved these parameters.

The role of the calcium-sensing receptor in disorders of abnormal calcium handling and cardiovascular disease

PURPOSE OF REVIEW

The calcium-sensing receptor (CaSR) has a central role in parathyroid gland function. Genetic alterations in CaSR are well known to cause inherited forms of abnormal calcium homeostasis. This review focuses on studies investigating the role of CaSR in common disorders of abnormal calcium handling and in cardiovascular calcification.

RECENT FINDINGS

Genetic population studies tested the association of common allelic CASR variants with serum and urine calcium levels, kidney stone disease, primary hyperparathyroidism and bone mineral density. The results of these association studies suggested either minor or no effects of CASR variants in these phenotypes. Decreased expression of CaSR was associated with the etiology of cardiovascular calcification in individuals with advanced chronic kidney disease.

SUMMARY

Ionized calcium plays a central role in the physiology of many organ systems and disease states, but the roles of CaSR other than as illustrated by Mendelian forms of CaSR dysfunction remain unclear. The contributions of CaSR to bone mineral homeostasis, vascular calcification and other forms of cardiovascular disease need further investigation.

Increased trabecular volumetric bone mass density in Familial Hypocalciuric Hypercalcemia (FHH) type 1: a cross-sectional study

Familial Hypocalciuric Hypercalcaemia (FHH) Type 1 is caused by an inactivating mutation in the calcium-sensing receptor (CASR) gene resulting in elevated plasma calcium levels. We investigated whether FHH is associated with change in bone density and structure. We compared 50 FHH patients with age- and gender-matched population-based controls (mean age 56 years, 69 % females). We assessed areal BMD (aBMD) by DXA-scans and total, cortical, and trabecular volumetric BMD (vBMD) as well as bone geometry by quantitative computed tomography (QCT) and High-Resolution peripheral-QCT (HR-pQCT). Compared with controls, FHH females had a higher total and trabecular hip vBMD and a lower cortical vBMD and hip bone volume. Areal BMD and HRpQCT indices did not differ except an increased trabecular thickness and an increased vBMD at the transition zone between cancellous and cortical bone in of the tibia in FHH. Finite element analyses showed no differences in bone strength. Multiple regression analyses revealed correlations between vBMD and P-Ca(2+) levels but not with P-PTH. Overall, bone health does not seem to be impaired in patients with FHH. In FHH females, bone volume is decreased, with a lower trabecular volume but a higher vBMD, whereas cortical vBMD is decreased in the hip. This may be due to either an impaired endosteal resorption or corticalization of trabecular bone. The smaller total bone volume suggests an impaired periosteal accrual, but bone strength is not impaired. The findings of more pronounced changes in females may suggest an interaction between sex hormones and the activity of the CaSR on bone.