Diagnosis of asymptomatic primary hyperparathyroidism: proceedings of the third international workshop

The changing profile of patients with calcium nephrolithiasis and the ascendancy of overweight and obesity: a comparison of two patient series observed 25 years apart

BACKGROUND

Epidemiological data indicate an increasing incidence and prevalence of nephrolithiasis (NL) worldwide in the last few decades.

METHODS

The aim of this study was to compare the clinical and biochemical profiles of recurrent stone formers referred to a Kidney Stone Centre from March 1983 to June 1986 with the one featured by patients seen 25 years later in the same geographical area, Campania, southern Italy.

RESULTS

Idiopathic calcium stone formers made up the large majority of the patient population in both series. Those examined in 2008-11 showed higher age at the onset of NL, higher prevalence of overweight/obesity and higher urinary excretion of oxalate and phosphate compared with those seen in 1983-86. The differences in the urinary biochemical variables remained significant upon accounting for age, gender, creatinine clearance and body mass index (BMI), and were not observed in patients with primary hyperparathyroidism enrolled in the same periods. A greater prevalence of uric acid stone formers was also observed in the 2008-11 population.

CONCLUSIONS

The massive epidemics of overweight/obesity and the substantial modifications of dietary habits over the last few decades in most Western countries may be the factors underlying the changing clinical and biochemical profiles of patients with recurrent NL.

Relation of vitamin D and parathyroid hormone to cardiac biomarkers and to left ventricular mass (from the Cardiovascular Health Study)

Vitamin D and parathyroid hormone (PTH) may affect cardiovascular health in patients with kidney disease and in the general population. The aim of this study was to investigate associations of serum 25-hydroxyvitamin D (25(OH)D) and PTH concentrations with a comprehensive set of biochemical, electrocardiographic, and echocardiographic measurements of cardiac structure and function in the Cardiovascular Health Study. A total of 2,312 subjects who were free of cardiovascular disease at baseline were studied. Serum 25(OH)D and intact PTH concentrations were measured using mass spectrometry and a 2-site immunoassay. Outcomes were N-terminal pro-B-type natriuretic peptide, cardiac troponin T, electrocardiographic measures of conduction, and echocardiographic measures of left ventricular mass and diastolic dysfunction. At baseline, subjects had a mean age of 73.9 ± 4.9 years, 69.7% were women, and 21% had chronic kidney disease (glomerular filtration rate <60 ml/min). Mean 25(OH)D was 25.2 ± 10.2 ng/ml, and median PTH was 51 pg/ml (range 39 to 65). After adjustment, 25(OH)D was not associated with any of the biochemical, conduction, or echocardiographic outcomes. Serum PTH levels ≥65 pg/ml were associated with greater N-terminal pro-B-type natriuretic peptide, cardiac troponin T, and left ventricular mass in patients with chronic kidney disease. The regression coefficients were: 120 pg/ml (95% confidence interval 36.1 to 204), 5.2 pg/ml (95% confidence interval 3.0 to 7.4), and 17 g (95% confidence interval 6.2 to 27.8) (p <0.001). In subjects with normal kidney function, PTH was not associated with the outcomes. In conclusion, in older adults with chronic kidney disease, PTH excess is associated with higher N-terminal pro-B-type natriuretic peptide, cardiac troponin T, and left ventricular mass. These findings suggest a role for PTH in cardiovascular health and the prevention of cardiac diseases.

Medical management of primary hyperparathyroidism

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

Asymptomatic primary hyperparathyroidism

The clinical profile of primary hyperparathyroidism (PHPT) as it is seen in the United States and most Western countries has evolved significantly over the past half century. The introduction of the multichannel serum autoanalyzer in the 1970s led to the recognition of a cohort of individuals with asymptomatic hypercalcemia, in whom evaluation led to the diagnosis of PHPT. The term "asymptomatic primary hyperparathyroidism" was introduced to describe patients who lack obvious signs and symptoms referable to either excess calcium or parathyroid hormone. Although it was expected that asymptomatic patients would eventually develop classical symptoms of PHPT, observational data suggest that most patients do not evolve over time to become overtly symptomatic. In most parts of the world, the asymptomatic phenotype of PHPT has replaced classical PHPT. This report is a selective review of data on asymptomatic PHPT: its demographic features, presentation and natural history, as well as biochemical, skeletal, neuromuscular, psychological, and cardiovascular manifestations. In addition, we will summarize available information on treatment indications and options for those with asymptomatic disease.

Nonsurgical management of mild primary hyperparathyroidism - a reasonable option

Primary hyperparathyroidism (PHPT) is a relatively common disorder which is often diagnosed incidentally and characterized in the majority of those affected by mild stable biochemical abnormalities and lack of symptoms. Nephrolithiasis and bone loss leading to an increased risk of fracture are generally accepted complications of PHPT. Some epidemiological studies report associations between PHPT and a wide range of common diseases, but these relationships may be confounded by the increased body weight observed in PHPT. Because there is a dearth of controlled clinical trial evidence in PHPT, optimal management is controversial. For individuals with mild stable PHPT, low fracture risk and no renal stones, observation without intervention is reasonable. Surgical treatment is clearly indicated for patients at risk of severe hypercalcaemia or with nephrolithiasis. For individuals with increased risk of fracture, antiresorptive therapies improve bone mineral density to a similar degree to surgical treatment. Calcimimetic agents may have a role in managing patients with symptomatic PHPT who cannot undergo, or fail, surgical treatment. There is a need for additional randomized clinical trials to inform management of PHPT.

Effects of age and serum 25-OH-vitamin D on serum parathyroid hormone levels

CONTEXT

Several studies define optimal serum 25-hydroxyvitamin D (25-OHD) levels based on serum PTH level reaching an asymptote. However, results differ widely, ranging from 25-OHD levels of 12-44 ng/ml: many studies are constrained by small sample size.

OBJECTIVE

The objective of the study was to determine the relationship between serum PTH and 25-OHD levels and age in a very large reference laboratory database.

DESIGN

This was a detailed cross-sectional analysis of 312,962 paired serum PTH and 25-OHD levels measured from July 2010 to June 2011.

RESULTS

Median PTH levels and the proportion of patients (PTH > 65 pg/ml), from 63 successive 25-OHD frequency classes of 5000 patients, provide smooth, exceptionally well-fitted curves (R(2) = 0.994 and R(2) = 0.995, respectively) without discernible inflection points or asymptotes but with striking age dependencies. Serum 25-OHD was below the recent Institute of Medicine sufficiency guidance of 20 ng/ml in 27% (85,000) of the subjects. More importantly, 40 and 51% of subjects (serum 25-OHD <20 and 10 ng/ml, respectively) had biochemical hyperparathyroidism (PTH > 65 pg/ml).

CONCLUSIONS

This analysis, despite inevitable inherent limitations, introduces several clinical implications. First, median 25-OHD-dependent PTH levels revealed no threshold above which increasing 25-OHD fails to further suppress PTH. Second, the large number of subjects with 25-OHD deficiency and hyperparathyroidism reinforces the Third International Workshop on Asymptomatic Primary Hyper parathyroidism's recommendations to test for, and replete, vitamin D depletion before considering parathyroidectomy. Third, strong age dependency of the PTH-25-OHD relationship likely reflects the composite effects of age-related decline in calcium absorption and renal function. Finally, this unselected large population database study could guide clinical management of patients based on an age-dependent, PTH-25-OHD continuum.

Surgeon beware: many patients referred for parathyroidectomy are misdiagnosed with primary hyperparathyroidism

PURPOSE

We hypothesized that patients referred for the evaluation and management of primary hyperparathyroidism (pHPT) often do not have pHPT and that they may be harmed by unwarranted parathyroidectomy (PTX).

METHODS

We reviewed all patients who were referred to our endocrine surgery practice between 2008 and 2011 with International Classification of Diseases, Ninth Revision codes for HPT (252.00), benign or malignant parathyroid tumors (227.1, 194.1, respectively), or hypercalcemia (275.42). Patients with renal failure were excluded. Clinical parameters for investigation included age, sex, presentation, laboratories, imaging studies, and referring physician.

RESULTS

Three hundred twenty-four patients were referred for pHPT. The diagnosis was confirmed in 265 (82%), of whom 211 (80%) underwent PTX. Misdiagnoses occurred in 60 of 324 patients (19%). Of these, 54 (90%) had secondary HPT and 6 (10%) had hypercalcemia but no pHPT. Before referral, 70% of misdiagnosed patients underwent localizing studies, 57% of which suggested a positive finding.

CONCLUSION

Considerable confusion exists regarding the differentiation of primary and secondary HPT. Surgeons should be cautioned that patients who are referred for parathyroidectomy, even those with complete laboratory and radiographic evaluations, might not have pHPT at all.

Effect of eplerenone on parathyroid hormone levels in patients with primary hyperparathyroidism: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Increasing evidence suggests the bidirectional interplay between parathyroid hormone and aldosterone as an important mechanism behind the increased risk of cardiovascular damage and bone disease observed in primary hyperparathyroidism. Our primary object is to assess the efficacy of the mineralocorticoid receptor-blocker eplerenone to reduce parathyroid hormone secretion in patients with parathyroid hormone excess.

METHODS/DESIGN

Overall, 110 adult male and female patients with primary hyperparathyroidism will be randomly assigned to eplerenone (25 mg once daily for 4 weeks and 4 weeks with 50 mg once daily after dose titration] or placebo, over eight weeks. Each participant will undergo detailed clinical assessment, including anthropometric evaluation, 24-h ambulatory arterial blood pressure monitoring, echocardiography, kidney function and detailed laboratory determination of biomarkers of bone metabolism and cardiovascular disease.The study comprises the following exploratory endpoints: mean change from baseline to week eight in (1) parathyroid hormone(1-84) as the primary endpoint and (2) 24-h systolic and diastolic ambulatory blood pressure levels, NT-pro-BNP, biomarkers of bone metabolism, 24-h urinary protein/albumin excretion and echocardiographic parameters reflecting systolic and diastolic function as well as cardiac dimensions, as secondary endpoints.

DISCUSSION

In view of the reciprocal interaction between aldosterone and parathyroid hormone and the potentially ensuing target organ damage, the EPATH trial is designed to determine whether eplerenone, compared to placebo, will effectively impact on parathyroid hormone secretion and improve cardiovascular, renal and bone health in patients with primary hyperparathyroidism.

TRIAL REGISTRATION

ISRCTN33941607.

Surgical management of normocalcemic primary hyperparathyroidism

BACKGROUND

Primary hyperparathyroidism (pHPT), typically defined as elevated serum calcium levels associated with inappropriately elevated parathyroid hormone (PTH) levels, can occur also in patients with normal serum calcium levels. This study investigated the characteristics, workup, and surgical management of patients with normocalcemic pHPT.

METHODS

A retrospective chart review of a prospectively collected, single-institution parathyroid database was performed on patients with sporadic pHPT who underwent parathyroidectomy between 12/99 and 12/08.

RESULTS

In all, 93 of 771 (12%) pHPT patients had normal serum calcium levels 3 months prior to surgery. Ionized calcium (iCa) levels were available for 58 patients and were elevated in 50 (86%). Among those with elevated iCa levels 90% had single-gland disease (SGD), whereas 63% with normal iCa levels had SGD (p = 0.07). Preoperative imaging identified SGD in 60% of patients with normal iCa and in 66% with elevated iCa levels. Intraoperative PTH (IOPTH) monitoring identified cure in 51 of 58 (88%) patients including 6 (75%) with normal iCa. At a median follow-up of 358 days, postoperative calcium and PTH levels were similar in the groups. One (1%) patient had recurrent disease.

CONCLUSIONS

Most patients with apparent normocalcemic pHPT have elevated ionized calcium levels. For patients with normocalcemic pHPT, we recommend measuring iCa levels preoperatively, performing localization studies, and utilizing IOPTH monitoring to guide a successful operation.

Persistent primary hyperparathyroidism: an uncommon location for an ectopic gland - Case report and review

Primary hyperparathyroidism (PHPT) is a common endocrine disorder that mainly affects middle-aged women. Patients are usually asymptomatic. The disease might be ascribable to hyperplasia, carcinoma, and single or multiple adenomas. PHPT may be sporadic or familial, the latter comprising multiple endocrine neoplasia type 1 or 2A, familial benign hypocalciuria hypercalcemia, and hyperparathyroidism-jaw tumor syndrome. The most common causes for persistent PHPT are multiglandular disease, and missed abnormal ectopic or orthotopic parathyroid glands. Imaging localization studies should precede a new surgical intervention. Ectopic parathyroid glands are rarely located at the aortopulmonary window. For diagnosis confirmation, 99mTc-sestamibi SPECT/CT seems to be an advantageous test. Another possibility is to perform 99mTc-sestamibi followed by thoracic CT or MRI. Parathyroidectomy may be performed by means of median sternotomy, thoracotomy, or video-assisted thoracoscopy. We describe a case of persistent primary hyperparathyroidism due to the presence of an ectopic parathyroid gland found at the aortopulmonary window. As the investigation necessary to clarify the etiology of recurrent nephrolithiasis proceeded, the diagnosis of PHPT was determined. The patient underwent subtotal parathyroidectomy; nevertheless, PHPT persisted. Genetic syndromes that could account for this condition were excluded. Imaging studies available at that time were not able to locate abnormal glands; moreover, the patient refused to undergo surgical exploration. Later, the patient underwent 99mTc-sestamibi SPECT/CT, which revealed a parathyroid gland at the aortopulmonary window.

Diagnosis and management of primary hyperparathyroidism in Europe

BACKGROUND

There is continued debate as to the optimal strategy for diagnosis and management of primary hyperparathyroidism (PHPT).

AIM

To compare the strategies used for the diagnosis and management of PHPT by physicians in five European countries.

DESIGN

Questionnaire-based survey.

METHODS

Physicians in France, Germany, the UK, Italy and Spain were invited to participate in the survey which was conducted using a web-based interface and were included in the evaluation if they had treated a minimum of four patients suffering from PHPT in the past year.

RESULTS

A total of 421 physicians completed the survey. The majority of respondents were endocrinologists (68%) but other specialities included rheumatologists (10.9%), internists (11.8%) and urologists (9.2%). Diagnostic methods were similar across different countries and specialities but there were significant differences in the proportion of physicians who recommended parathyroidectomy in asymptomatic patients with indications for surgery according to the 2002 National Institutes of Health (NIH) consensus conference statement (χ(2 )= 26.1, P < 0.001). The proportion of patients referred for surgery ranged from 32% in Italy to 66% in Spain with intermediate values in Germany (64%), France (55%) and the UK (53%). Conversely, pharmacological therapy was used most frequently for these patients in Italy (32%) and least frequently in Spain (14%).

CONCLUSION

Significant differences exist in the management of patients with asymptomatic PHPT in countries across Europe who have accepted indications for surgery according to the NIH consensus statement. Further research will be required to explore the reasons for this and to determine if these differences affect the clinical outcome of PHPT.

Impact of vitamin D-related serum PTH reference values on the diagnosis of mild primary hyperparathyroidism, using bivariate calcium/PTH reference regions

BACKGROUND, OBJECTIVE: An international consensus conference underlined the importance of defining upper parathyroid hormone (PTH) reference values based on 25-OH-vitamin D [25(OH)D] to diagnose mild primary hyperparathyroidism. We determined the importance of this factor in a Belgian population.

DESIGN, PATIENTS, METHODS

Intact PTH and 25(OH)D were measured in 261 healthy controls (18-65 years, winter/summer). They were classified as 25(OH)D replete (50-153 nmol/l; n = 129) or deplete (8-50 nmol/l; n = 132). PTH was determined in 49 patients with surgically proven primary hyperparathyroidism. PTH thresholds for 95% specificities and corresponding sensitivities were computed from both 25(OH)D replete and deplete receiver operating characteristic (ROC) curves. The 95% bivariate reference ellipses, relating PTH to calcium for 25(OH)D replete and deplete controls, were compared to the PTH/calcium pairs of patients with primary hyperparathyroidism.

RESULTS

Parathyroid hormone correlated with 25(OH)D (r = -0.3232; P < 0.0001). PTH normative values were 20% lower in 25(OH)D replete than deplete controls (P < 0.0001). PTH thresholds, providing 95% specificities for primary hyperparathyroidism diagnosis, were 7.6 pmol/l and 5.8 pmol/l, using ROC curves derived from 25(OH)D deplete or replete controls, respectively. Corresponding sensitivities were of 56%vs 88%, respectively (P < 0.05). The 95% PTH/calcium bivariate reference ellipses for?deplete and replete 25(OH)D controls differed, but the PTH/calcium pairs of patients with primary hyperparathyroidism did not overlap these ellipses.

CONCLUSION

For a given specificity, primary hyperparathyroidism diagnostic parathyroid hormone thresholds were lower and sensitivities higher using ROC curves, derived from 25(OH)D replete vs deplete controls. The 25(OH)D status does not affect the efficiency of primary hyperparathyroidism diagnosis, using bivariate PTH/calcium reference density ellipses.

Variation in parathyroid hormone immunoassay results--a critical governance issue in the management of chronic kidney disease

Renal physicians strive to maintain parathyroid hormone (PTH) concentrations for patients with chronic kidney disease (CKD) within guideline limits, but poor method comparability means there is currently serious risk of clinical misclassification. The potential for under- or over-treatment is significant, representing a major challenge to patient safety. In the short-term, raising awareness of clinical implications of method-related differences in PTH is essential. Agreeing and adopting assay-specific PTH action limits for CKD patients as an interim measure is highly desirable and has been achieved in Scotland. Establishing pre-analytical requirements for PTH is also a priority. In the longer term, re-standardization of PTH methods in terms of an appropriate International Standard is required. Provided commutability can be demonstrated, the recently established IS 95/646 for PTH (1-84) is a suitable candidate. Establishment of a well-characterized panel of samples of defined clinical provenance to enable manufacturers to determine appropriate reference intervals and clinical decision points is also recommended and will provide an invaluable clinical resource. Recent developments in mass spectrometry mean that a candidate reference measurement procedure for PTH is now achievable and will represent major progress. Concurrently, evidence-based recommendations on clinical requirements and performance goals for PTH are required. Improving the comparability of PTH results requires support from many stakeholders but is achievable.

Low urine calcium excretion in African American patients with primary hyperparathyroidism

OBJECTIVE

To evaluate the prevalence of low urine calcium excretion in African American patients with primary hyperparathyroidism (PHPT), a common disorder associated with bone and renal complications, and to assess the distinction between PHPT and familial hypocalciuric hypercalcemia (FHH), a rare benign genetic disease.

METHODS

We conducted a retrospective study on a cohort of 1,297 patients in whom a 24-hour urine study was performed for measurement of urine calcium and creatinine. PHPT was diagnosed if the serum calcium concentration was ≥10.5 mg/dL and intact parathyroid hormone (PTH) was ≥40 pg/mL. Patients receiving medications that affect urine calcium or with glomerular filtration rate ≤30 mL/min were excluded.

RESULTS

Ninety-six patients satisfied the diagnostic criteria for PHPT. The African American (n = 70) and non-African American (n = 26) patients did not differ in their mean age, body mass index, glomerular filtration rate, serum PTH, 25-hydroxyvitamin D levels, and 24-hour urine creatinine values. Median values of urine calcium/creatinine (mg/g) were 122 for African American versus 214 for non-African American patients (P = .006). Thirty-one of 70 African American patients (44%) had a urine calcium/creatinine ratio ≤100 mg/g, whereas only 2 of 26 non-African American patients (8%) had this value (P = .001).

CONCLUSION

The prevalence of low urine calcium excretion among African American patients with PHPT is unexpectedly high. A threshold of 100 mg/g urine calcium/creatinine identified 44% of such patients with PHPT as having FHH in this cohort. Therefore, other clinical criteria and laboratory variables should be used to distinguish PHPT from FHH in African American patients with PTH-dependent hypercalcemia.

Vitamin D: an essential component for skeletal health

Vitamin D deficiency is increasing worldwide. Ultraviolet rays are supposed to provide humans over 80% of our vitamin D requirement; the rest is received through diet and supplements. In addition to enhancing calcium absorption from the intestine and mineralization of the osteoid tissue, vitamin D has many other physiological effects, including neuromodulation, improving muscle strength and coordination, insulin release, immunity and prevention of infections, and curtailing cancer. Whether the increased incidence of vitamin D deficiency is related to increased incidences of nonskeletal disorders remains to be determined. Serum levels of 25-hydroxyvitamin [25(OH)D] above 30 ng/mL indicate vitamin D sufficiency. An additional 1,000 IU of vitamin D/day is sufficient for most lighter-skinned individuals, whereas an extra 2,000 IU/day is needed by the elderly and dark-skinned individuals to maintain normal 25(OH)D levels. Additional research is needed to clarify the relationship between vitamin D and the nonskeletal systems, nonclassic functions, and targets of vitamin D.

Primary hyperparathyroidism and celiac disease: a population-based cohort study

CONTEXT

Celiac disease (CD) has been linked to several endocrine disorders, including type 1 diabetes and thyroid disorders, but little is known regarding its association to primary hyperparathyroidism (PHPT).

OBJECTIVE

The aim of the study was to examine the risk of PHPT in patients with CD.

DESIGN AND SETTING

We conducted a two-group exposure-matched nonconcurrent cohort study in Sweden. A Cox regression model estimated hazard ratios (HR) for PHPT.

PARTICIPANTS

We identified 17,121 adult patients with CD who were diagnosed through biopsy reports (Marsh 3, villous atrophy) from all 28 pathology departments in Sweden. Biopsies were performed in 1969-2008, and biopsy report data were collected in 2006-2008. Statistics Sweden then identified 85,166 reference individuals matched with the CD patients for age, sex, calendar period, and county.

MAIN OUTCOME MEASURE

PHPT was measured according to the Swedish national registers on inpatient care, outpatient care, day surgery, and cancer.

RESULTS

During follow-up, 68 patients with CD and 172 reference individuals developed PHPT (HR=1.91; 95% confidence interval=1.44-2.52). The absolute risk of PHPT was 42/100,000 person-years with an excess risk of 20/100,000 person-years. The risk increase for PHPT only occurred in the first 5 yr of follow-up; after that, HR were close to 1 (HR=1.07; 95% confidence interval=0.70-1.66).

CONCLUSIONS

CD patients are at increased risk of PHPT, but the absolute risk is small, and the excess risk disappeared after more than 5 yr of follow-up.

Vitamin D in the new millennium

The incidence of vitamin D deficiency is rising worldwide, yet in the vast majority of patients, the condition remains undiagnosed and untreated. Current evidence overwhelmingly indicates that supplemental doses greater than 800 IU/day have beneficial effects on the musculoskeletal system, improving skeletal homeostasis, thus leading to fewer falls and fractures. Evidence is also accumulating on the beneficial effects of vitamin D on extraskeletal systems, such as improving immune health, autoimmune disorders, cancer, neuromodulation, diabetes, and metabolic syndrome. The cause-effect relationship of vitamin D deficiency with increasing incidences of nonskeletal disorders is being investigated. Published reports support the definition of sufficiency, serum levels of 25-hydroxyvitamin D [25(OH)D] greater than 30 ng/mL (75 nmol/L). To achieve this, most people need vitamin D supplementation ranging from 600 to 2000 IU/day; consumption up to of 5000 international units (IU) per day of vitamin D is reported as safe. Although light-skinned individuals need 1000 IU/day of vitamin D, elderly and dark-skinned individuals are likely to need approximately 2000 IU/day to maintain serum 25(OH)D levels greater than 30 ng/mL. Other vulnerable patients, such as the obese, those who have undergone bariatric surgery, and those with gastrointestinal malabsorption syndromes, may require higher doses of vitamin D to maintain normal serum levels and be healthy.

Renal manifestations of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) is associated with nephrolithiasis and nephrocalcinosis. Hypercalciuria is one of the multiple factors that is implicated in the complex pathophysiology of stone formation. The presence of a renal stone (symptomatic or asymptomatic) categorizes PHPT as symptomatic and is an indication for parathyroid adenomectomy. Progression of nephrocalcinosis is largely reversible after successful surgery, but the residual risk persists. PHPT is also associated with declining renal function. In case of asymptomatic mild PHPT, annual renal functional assessment is advised. Guidelines suggest that an estimated glomerular filtration rate (eGFR) < 60 ml / minute / 1.73 m(2) is an indication for parathyroid adenomectomy. This article discusses how to monitor and manage renal stones and other related renal parameters in case of PHPT.

[Clinical practice guidelines for evaluation and treatment of osteoporosis associated to endocrine and nutritional conditions. Bone Metabolism Working Group of the Spanish Society of Endocrinology]

OBJECTIVE

To provide practical recommendations for evaluation and treatment of osteoporosis associated to endocrine diseases and nutritional conditions.

PARTICIPANTS

Members of the Bone Metabolism Working Group of the Spanish Society of Endocrinology, a methodologist, and a documentalist.

METHODS

Recommendations were formulated according to the GRADE system (Grading of Recommendations, Assessment, Development, and Evaluation) to describe both the strength of recommendations and the quality of evidence. A systematic search was made in MEDLINE (Pubmed), using the following terms associated to the name of each condition: AND "osteoporosis", "fractures", "bone mineral density", and "treatment". Papers in English with publication date before 18 October 2011 were included. Current evidence for each disease was reviewed by two group members, and doubts related to the review process or development of recommendations were resolved by the methodologist. Finally, recommendations were discussed in a meeting of the Working Group.

CONCLUSIONS

The document provides evidence-based practical recommendations for evaluation and management of endocrine and nutritional diseases associated to low bone mass or an increased risk of fracture. For each disease, the associated risk of low bone mass and fragility fractures is given, recommendations for bone mass assessment are provided, and treatment options that have shown to be effective for increasing bone mass and/or to decreasing fragility fractures are listed.

PTH Assays: Understanding What We Have and Forecasting What We Will Have

Parathyroid hormone (PTH) assays have evolved continuously for the last 50 years. Since the first radioimmunoassay was described in 1963, several assays based on immunological identification have been published (first generation assays). The routine assays used nowadays are immunometric "sandwich-type". They are based on two different monoclonal antibodies, one amino-terminal and the other carboxyl terminal specific. These second generation assays are widely available and adapted to most of the automation platforms. The specificity of the amino terminal antibody defines if the immunometric assay measures only the bioactive PTH circulating form (including the first amino terminal amino acids) or the "intact" PTH, which includes, besides bioactive PTH, other "long" carboxyl-terminal forms, for example, 7-84-PTH. Assays for "intact" PTH are the most commonly available and the potential advantage of the bioactive PTH assays is still debatable. Next generation of assays will be based on different principles, mainly mass spectrometry in samples submitted to a prior purification and fragmentation steps. These assays will provide information about the whole spectra of PTH peptides in circulation, with a significant increase of the information regarding this biologically important peptide hormone.

Post-surgical follow-up of primary hyperparathyroidism associated with multiple endocrine neoplasia type 1

The bone mineral density increments in patients with sporadic primary hyperparathyroidism after parathyroidectomy have been studied by several investigators, but few have investigated this topic in primary hyperparathyroidism associated with multiple endocrine neoplasia type 1. Further, as far as we know, only two studies have consistently evaluated bone mineral density values after parathyroidectomy in cases of primary hyperparathyroidism associated with multiple endocrine neoplasia type 1. Here we revised the impact of parathyroidectomy (particularly total parathyroidectomy followed by autologous parathyroid implant into the forearm) on bone mineral density values in patients with primary hyperparathyroidism associated with multiple endocrine neoplasia type 1. Significant increases in bone mineral density in the lumbar spine and femoral neck values were found, although no short-term (15 months) improvement in bone mineral density at the proximal third of the distal radius was observed. Additionally, short-term and medium-term calcium and parathyroid hormone values after parathyroidectomy in patients with primary hyperparathyroidism associated with multiple endocrine neoplasia type 1 are discussed. In most cases, this surgical approach was able to restore normal calcium/parathyroid hormone levels and ultimately lead to discontinuation of calcium and calcitriol supplementation.

Vitamin D status in primary hyperparathyroidism

BACKGROUND

Hypovitaminosis D worsens the manifestations of primary hyperparathyroidism (PHPT). Only a few studies have assessed the status of vitamin D in PHPT. The objective of this study was to determine the prevalence of 25(OH)D levels<50 nmol/L in PHPT in comparison to a population without PHPT.

METHODS

Subjects with PHPT were identified from the computerized database of the Clalit Health Services in Israel and were included only if they had an available serum 25(OH)D test result in 2009 and were not taking vitamin D supplements in 2008-2009 prior to the 25(OH)D test result. Subjects with renal failure were excluded (included n=1180). All other subjects with an available 25(OH)D value in 2009 constituted the control group (n=184,479).

RESULTS

Subjects with PHPT and 25(OH)D<50 nmol/L had higher levels of serum PTH, alkaline phosphatase, and calcium levels compared to those with 25(OH)D levels≥50 nmol/L (P<0.02). The mean serum 25(OH)D level was 47.7±22.5 nmol/L compared to 52.1±24.5 nmol/L in the control group (P<0.001). 59.6% of subjects with PHPT had 25(OH)D levels<50 nmol/L as compared to 49.5% in the control group (P<0.001). Logistic regression, controlling for gender, ethnicity, age, and seasonality, showed that PHPT independently predicted 25(OH)D levels<50 nmol/L; OR=1.61(95% CI, 1.43-1.82).

CONCLUSIONS

Serum 25(OH)D levels<50 nmol/L are frequent in PHPT, are more common than in controls, and are associated with more severe bone disease based on higher serum PTH and bone turnover biomarkers.

Total parathyroidectomy in a large cohort of cases with hyperparathyroidism associated with multiple endocrine neoplasia type 1: experience from a single academic center

Most cases of sporadic primary hyperparathyroidism present disturbances in a single parathyroid gland and the surgery of choice is adenomectomy. Conversely, hyperparathyroidism associated with multiple endocrine neoplasia type 1 (hyperparathyroidism/multiple endocrine neoplasia type 1) is an asynchronic, asymmetrical multiglandular disease and it is surgically approached by either subtotal parathyroidectomy or total parathyroidectomy followed by parathyroid auto-implant to the forearm. In skilful hands, the efficacy of both approaches is similar and both should be complemented by prophylactic thymectomy. In a single academic center, 83 cases of hyperparathyroidism/ multiple endocrine neoplasia type 1 were operated on from 1987 to 2010 and our first surgical choice was total parathyroidectomy followed by parathyroid auto-implant to the non-dominant forearm and, since 1997, associated transcervical thymectomy to prevent thymic carcinoid. Overall, 40% of patients were given calcium replacement (mean intake 1.6 g/day) during the first months after surgery, and this fell to 28% in patients with longer follow-up. These findings indicate that several months may be needed in order to achieve a proper secretion by the parathyroid auto-implant. Hyperparathyroidism recurrence was observed in up to 15% of cases several years after the initial surgery. Thus, long-term follow-up is recommended for such cases. We conclude that, despite a tendency to subtotal parathyroidectomy worldwide, total parathyroidectomy followed by parathyroid auto-implant is a valid surgical option to treat hyperparathyroidism/multiple endocrine neoplasia type 1. Larger comparative systematic studies are needed to define the best surgical approach to hyperparathyroidism/multiple endocrine neoplasia type 1.

The relationship between serum 25(OH)D and parathyroid hormone levels

OBJECTIVE

Low 25(OH)D levels are associated with increased parathyroid hormone levels leading to progressive bone loss. The serum levels of 25(OH)D sufficient to keep the parathyroid hormone level at a range that will prevent bone loss are still unclear. The current study was aimed at evaluating the relationship between 25(OH)D levels and concomitant parathyroid hormone levels.

METHODS

The computerized laboratory database of Clalit Health Services, a not-for-profit health maintenance organization covering more than half of the Israeli population, was searched for all 25(OH)D and parathyroid hormone tests performed in 2009. Concomitant tests of parathyroid hormone and 25(OH)D were identified in 19,172 people.

RESULTS

Serum parathyroid hormone levels were inversely correlated with 25(OH)D levels (r = -0.176, P < .001); 25(OH)D levels less than 50 nmol/L were associated with a steep increase in parathyroid hormone levels and hyperparathyroidism, which decreased with increasing 25(OH)D levels and reached a plateau at 25(OH)D levels of 75 to 85 nmol/L. The quadratic fit with plateau model showed that parathyroid hormone stabilizes at 25(OH)D level of 78.9 nmol/L. However, after excluding 5449 people with hypercalcemia or renal failure, the parathyroid hormone plateau was attained at a significantly lower 25(OH)D cut point of 46.2 nmol/L.

CONCLUSION

Our data suggest that a 25(OH)D threshold of 50 nmol/L is sufficient for parathyroid hormone suppression and prevention of secondary hyperparathyroidism in persons with normal renal function. 25(OH)D levels greater than 75 nmol/L do not seem to be associated with additional change in parathyroid hormone levels.

Vitamin D, parathyroid hormone, and cardiovascular events among older adults

OBJECTIVES

The aim of this study was to evaluate associations of 25-hydroxyvitamin D (25-OHD) and parathyroid hormone (PTH) concentrations separately and in combination with incident cardiovascular events and mortality during 14 years of follow-up in the CHS (Cardiovascular Health Study).

BACKGROUND

Vitamin D deficiency and PTH excess are common in older adults and may adversely affect cardiovascular health.

METHODS

A total of 2,312 participants who were free of cardiovascular disease at baseline were studied. Vitamin D and intact PTH were measured from previously frozen serum using mass spectrometry and a 2-site immunoassay. Outcomes were adjudicated cases of myocardial infarction, heart failure, cardiovascular death, and all-cause mortality.

RESULTS

There were 384 participants (17%) with serum 25-OHD concentrations <15 ng/ml and 570 (25%) with serum PTH concentrations ≥ 65 pg/ml. After adjustment, each 10 ng/ml lower 25-OHD concentration was associated with a 9% greater (95% confidence interval [CI]: 2% to 17% greater) relative hazard of mortality and a 25% greater (95% CI: 8% to 44% greater) relative hazard of myocardial infarction. Serum 25-OHD concentrations <15 ng/ml were associated with a 29% greater (95% CI: 5% to 55% greater) risk for mortality. Serum PTH concentrations ≥ 65 pg/ml were associated with a 30% greater risk for heart failure (95% CI: 6% to 61% greater) but not other outcomes. There was no evidence of an interaction between serum 25-OHD and PTH concentrations and cardiovascular events.

CONCLUSIONS

Among older adults, 25-OHD deficiency is associated with myocardial infarction and mortality; PTH excess is associated with heart failure. Vitamin D and PTH might influence cardiovascular risk through divergent pathways.

What medical options should be considered for the treatment of primary hyperparathyroidism?

Primary hyperparathyroidism (PHPT) is a common, often asymptomatic, endocrine disorder characterized by hypercalcaemia in the face of a nonsuppressed parathyroid hormone (PTH) level. For those with symptomatic disease or who meet surgical criteria, parathyroidectomy is the treatment of choice. However, those patients who do not meet surgical criteria or who cannot undergo or refuse surgery must be managed medically. Medical management of PHPT involves continual assessment to determine who will benefit from surgical intervention, replacement of vitamin D, treatment of parathyroid bone disease and management of hypercalcaemia and renal stone disease.

Hypoparathyroidism in the adult: epidemiology, diagnosis, pathophysiology, target-organ involvement, treatment, and challenges for future research

Recent advances in understanding the epidemiology, genetics, diagnosis, clinical presentations, skeletal involvement, and therapeutic approaches to hypoparathyroidism led to the First International Workshop on Hypoparathyroidism that was held in 2009. At this conference, a group of experts convened to discuss these issues with a view towards a future research agenda for this disease. This review, which focuses primarily on hypoparathyroidism in the adult, provides a comprehensive summary of the latest information on this disease.

Interpretation of serum PTH concentrations with different kits in dialysis patients according to the KDIGO guidelines: importance of the reference (normal) values

BACKGROUND

The recommended target range for serum parathyroid hormone (PTH) in dialysis patients has changed from 150 to 300 pg/mL in the KDOQI guidelines to two to nine times the upper normal limit in the KDIGO ones. Although inclusion/exclusion criteria for the reference population are highly important, they are usually not mentioned in the commercial kits. In this study, we used the same reference population of vitamin D-replete normal subjects to establish reference values for 10 commercial PTH kits. We evaluated whether this may improve the classification of dialysis patients according to the KDIGO compared to the use of reference values proposed by the manufacturers.

METHODS

We measured serum PTH with 10 different kits in 149 haemodialysis patients, and 240 25-OH-vitamin D-replete (>75 nmol/L) individuals with an estimated glomerular filtration rate >60 mL/min/1.73 m(2).

RESULTS

For the 10 kits, our upper normal limit was lower than those of the manufacturers. The difference was, however, variable from one kit to another. The two kits that yielded the lowest and the highest absolute concentrations classified differently 84/149 patients (56.4%) according to the KDOQI and 53/149 (36.2%) according to the KDIGO using the manufacturers' normal values. Using our normal values significantly decreased the discrepancies with 24/149 patients (16.1%) being still classified differently. Taking the measurement uncertainty into consideration, 8% of the patients only remained differently classified by these two kits.

CONCLUSIONS

Using the same vitamin-D-replete population to establish the reference range for 10 commercial PTH kits significantly improved the classification of haemodialysis patients according to the KDIGO target range.

Why modest but widespread improvement of the vitamin D status is the best strategy?

Vitamin D is a precursor for a secosteroid ligand of a major transcription factor, VDR, and is vital for normal bone mineralization. It also regulates many other genes so that it may be involved in many extra skeletal health effects. The optimal vitamin D status is controversial but there is a wide unanimity that the vitamin D status can and should be improved for some risk groups. To normalize serum calcium homeostasis as based on normal levels of serum 1,25(OH)₂D₃ or parathyroid hormone, or to optimize intestinal calcium absorption or bone mineral density in adults or elderly subjects, serum 25OHD should be 20 ng/ml or higher. A daily vitamin D supplement of at least 400 IU or preferably 800 IU of vitamin D₃ can reduce the risk of fractures and probably also falls in elderly subjects, especially when combined with an optimal calcium intake. There is no formal proof of causality to define an optimal vitamin D intake or serum 25OHD based on its presumed extra skeletal health effects but the guidelines for bone health would probably eliminate also most negative extra skeletal health effects. The recommended vitamin D₃ supplement of 400-800 IU/d for adults also corresponds to the daily replacement dose calculated from metabolic clearance studies.

[Usefulness of genetic tests in familial hypocalciuric hypercalcemia with atypical clinical presentation]

OBJECTIVES

Biochemical tests related to calcium and phosphorus metabolism have traditionally been considered as a reliable tool to differentiate familial hypocalciuric hypercalcemia (FHH) from primary hyperparathyroidism (PHPT). However, diagnosis may sometimes be difficult even for experienced clinicians. Our objective was to assess the accuracy of diagnostic tests in FHH and the circumstances in which genetic studies are required.

PATIENTS AND METHODS

A descriptive study was conducted of two families with hypercalcemia and suspected atypical FHH. Urinary calcium excretion was measured in 24-hour urine using different tests (calcium excretion (CE), urinary calcium/creatinine clearance ratio (UCCR)), and serum PTH and 25-hydroxyvitamin D levels were tested. Index cases underwent genetic study.

RESULTS

One patient from the first family showed overt, persistent hypercalciuria with values more consistent with PHPT than with FHH if we consider, as proposed by guidelines, a UCCR lower than 0.01 as diagnostic of FHH and a value higher than 0.02 as diagnostic of PHPT. The index case of the second family underwent surgery for a parathyroid adenoma. Both cases had a mutation c. 164C>T (Pro55Leu) in exon 2 in heterozygosis.

CONCLUSIONS

According to current clinical guidelines, definitive diagnosis of FHH requires genetic confirmation, which allowed in our case for detection of two families with FHH and atypical clinical presentations. We think that rational use of genetic tests may avoid unnecessary surgery and excess monitoring costs.

Cinacalcet as alternative treatment for primary hyperparathyroidism: achievements and prospects

Primary hyperparathyroidism (pHPT), which most frequently occurs asymptomatically, is a common endocrine disease associated with increased morbidity and mortality. The newly introduced management guidelines as well as the recent availability of the first calcimimetic offer a highly promising therapeutic option for patients with pHPT. Cinacalcet, the first available calcimimetic, increases the sensitivity of the calcium-sensing receptor (CaR) to circulating serum calcium, thereby safely reducing serum calcium and PTH concentrations in patients with mild-to-moderate pHPT, intractable disease, and also parathyroid carcinoma. Cinacalcet has proved efficient in short- and long-term controls of hypercalcemia and, though bone mineral density was not improved, the available data point to cinacalcet as the treatment of choice in non-operable patients with pHPT. These results encompass a wide spectrum of disease severity. Results are pending as to whether cinacalcet decreases mortality and morbidity in pHPT, confirmation of which would conclusively recommend this drug as a valid alternative to surgery.

The natural history of treated and untreated primary hyperparathyroidism: the parathyroid epidemiology and audit research study

BACKGROUND

Primary hyperparathyroidism (PHPT) is a common endocrine disorder with the majority of cases being mild and untreated.

AIM

To provide an update on the natural history of treated and untreated PHPT.

DESIGN

Retrospective population-based observational study.

METHODS

From 1997 to 2006, a well-defined cohort of PHPT patients was established in Tayside, Scotland. Subsequent cohorts of 'mild untreated' and 'surgically treated' PHPT patients were selected for the present study. Their serum calcium (S-Ca) and PTH concentrations were followed until September 2009. Surgical outcomes were evaluated using hospital admission data.

RESULTS

A total of 904 'mild untreated' patients were identified (median follow-up=4.7 years), with a baseline median S-Ca of 2.62 mmol/l. A general decreased trend was observed in the S-Ca concentration for up to 12 years but an increasing trend in PTH (P<0.001 in both instances). Disease progression, defined as an increase in S-Ca concentration, was observed in 121 patients (13.4%). Twenty-six (2.9%) patients had undergone surgery during the subsequent follow-up period. Baseline age and PTH concentration were the only significant risk factors for disease progression. In comparison, there were 200 'surgically treated' patients (median follow-up=5.8 years). S-Ca was normalised after surgery, in 196 patients (98%). Hospital admissions for renal complications were reduced after surgery. In conclusion, most untreated patients with mild PHPT had no progression of S-Ca but approximately 15% did show some evidence of progression. Parathyroidectomy, with a high success rate, normalized the S-Ca in patients with PHPT.

[Increase of PTH in post-menopausal osteoporosis]

AIMS

Increased parathyroid values (PTH) serum values can be observed in postmenopausal women. However, the clinical repercussion and causes of this finding are poorly understood. This study has aimed to analyze the prevalence and conditions associated to the increased serum PTH levels in postmenopausal women with osteoporosis as well as their clinical characteristics.

METHODS

Post-menopausal women with osteoporosis were included in the study. PTH, 25-hydroxyvitamin D (25OHD), 24-h urinary calcium, glomerular filtration rate (GFR) and calcium intake were evaluated. The prevalence of increased PTH serum values and its relationship with vitamin D deficiency and insufficiency, kidney failure, hypercalciuria and calcium intake deficiency were evaluated, these being conditions that may increase PTH secretion.

RESULTS

A total of 204 postmenopausal women with osteoporosis with a mean age of 64 years were included. Increase PTH levels (>65 pg/ml) were observed in 35% and 5 women had primary hyperparathyroidism. Women with increased serum PTH levels were older (67 ± 9 years) were old than those with normal PTH levels (63 ± 11 years) (P=0.03). PTH elevation was associated to calcium intake deficiency (<800 mg/d) in 81% of the women, to a vitamin D deficiency and insufficiency in 55% and 86%, respectively, renal insufficiency in 35% and hypercalciuria in 17% of the patients. These values, however, did not differ when compared with patients with normal PTH serum levels. Serum PTH levels were related to age (r=0.19, P=0.01) but not to 25OHD or GFR values.

CONCLUSIONS

One third of the post-menopausal women with osteoporosis had elevated PTH levels. This was due to primary hyperparathyroidism in 10%. The prevalence of conditions associated to the increase in PTH (reduced calcium intake, 25-hydroxyvitamin D, renal failure and hypercalciuria) is similar to that observed in women with normal PTH values.

Clinical significance of vitamin D deficiency in primary hyperparathyroidism, and safety of vitamin D therapy

Vitamin D deficiency occurs more frequently in patients with primary hyperparathyroidism (PHPT) compared with the general population, and is usually associated with an aggravated form of the disease. Current guidelines recommend measurement of serum levels of 25-hydroxy vitamin D (25-OHD) in all patients with PHPT, and their repletion if the levels are less than 50 mmol/L (20 ng/mL). Limited data suggest that vitamin D treatment is generally safe in subjects with mild PHPT and coexisting vitamin D deficiency. Adverse effects include hypercalcuria and, less commonly, exacerbation of hypercalcemia. Well-designed trials are needed to evaluate the safety of vitamin D replacement therapy in a wide spectrum of patients with concomitant PHPT and vitamin D deficiency. These trials should address the impact of such therapy on the complications and course of PHPT.

Increased fracture risk in normocalcemic postmenopausal women with high parathyroid hormone levels: a 16-year follow-up study

High PTH levels increase bone turnover and decrease bone mineral density (BMD). Low plasma 25-hydroxyvitamin D (25OHD) levels cause secondary hyperparathyroidism, but the relative contribution of low 25OHD and high PTH levels on risk of fracture is largely unknown. Within the cohort of women (n = 2,016) included in the Danish Osteoporosis Prevention Study (DOPS), we studied risk of fracture according to parathyroid status. Analyses were performed on effects of high PTH levels (i.e., in the upper tertile, ≥4.5 pmol/L) on risk of incident fractures at different 25OHD levels during 16 years of follow-up. Incident fractures were assessed using a nationwide hospital discharge register. In addition, effects of high PTH levels on BMD and vertebral fractures were assessed by DXA scans and spinal X-ray examination after 10 years of follow-up. High PTH levels were associated with a decreased body mass index, adjusted BMD, and an increased risk of any fracture (HR = 1.41, 95% CI 1.11-1.79) as well as an increased risk of osteoporotic fractures (HR = 1.59, 95% CI 1.20-2.10). Plasma 25OHD levels per se did not affect fracture risk, but high PTH levels were associated with an increased fracture risk only at 25OHD levels <50 nmol/L and 50-80 nmol/L. High PTH levels did not increase risk of fracture at 25OHD levels >80 nmol/L. In conclusion, PTH levels in the upper part or above the upper level of the reference interval increase risk of fracture in the presence of low vitamin D levels.

Utility of the urine calcium-to-creatinine ratio to diagnose primary hyperparathyroidism in asymptomatic hypercalcaemic patients with vitamin D deficiency

Background

Primary hyperparathyroidism (PHP) is the most common cause of hypercalcaemia, and often requires surgical treatment. Familial hypocalciuric hypercalcaemia (FHH) has similar biochemical features to PHP, but requires no treatment. The most common biochemical method used to distinguish between PHP and FHH is the urine calcium-to-creatinine ratio (UCCR). Vitamin D deficiency may alter the renal excretion of calcium, but it is unclear how vitamin D deficiency affects the diagnostic performance of UCCR.

Aim

To examine the reliability of UCCR to detect PHP in patients presenting with asymptomatic hypercalcaemia, in the presence or absence of vitamin D deficiency.

Methods

One hundred and eighteen UCCR measurements from 97 asymptomatic hypercalcaemic patients diagnosed with PHP presenting to a single specialist endocrine unit were analysed retrospectively.

Results

A significantly higher proportion of UCCR measurements were <0.010 in patients with serum vitamin D <25 nmol/L when compared with patients with serum vitamin D >25 nmol/L, thus incorrectly suggesting the presence of FHH (proportion of measurements with UCCR >0.010: 11/48 [22.9%], vitamin D <25 nmol/L; 4/70 [5.7%], vitamin D >25 nmol/L; P < 0.001). Urine calcium concentration was 26% lower and serum parathyroid hormone (PTH) was 27% higher in patients with vitamin D deficiency when compared with patients without vitamin D deficiency.

Conclusions

These data suggest that the presence of vitamin D deficiency is associated with worsened PTH hypersecretion, impairment of urinary calcium excretion and reduced sensitivity of UCCR measurement with respect to the detection of PHP. These data have important clinical implications for the investigation and management of patients with asymptomatic hypercalcaemia.