Is parathyroidectomy safe and effective in patients with normocalcemic primary hyperparathyroidism?

Normocalcemic primary hyperparathyroidism: From pathophysiology to clinical management

Normocalcemic primary hyperparathyroidism (NPHPT), a variant of primary hyperparathyroidism (PHPT) characterized by persistently elevated parathyroid hormone (PTH) levels and normal serum calcium, has gained recognition as a substantial subset of PHPT cases. Despite its increasing prevalence, the precise pathophysiology and natural progression of NPHPT remain enigmatic. This in-depth literature review explores recent advancements in our understanding of NPHPT, encompassing pathophysiology, clinical presentation, diagnostic approaches, medical and surgical management options. By synthesizing this wealth of information, this review aims to contribute to a more nuanced and informed approach to the treatment of patients grappling with NPHPT. As our understanding of the condition continues to evolve, the knowledge gathered from this review has the potential to significantly enhance the quality of care and outcomes for individuals afflicted with NPHPT, ultimately improving their overall well-being and prognosis.

Natural history and complications of normocalcemic hyperparathyroidism: a retrospective cohort study

Normocalcemic hyperparathyroidism (NHPT) is variably defined, and information regarding complications and natural history are scarce. We aimed to describe the phenotype of NHPT in relation to hypercalcemic hyperparathyroidism (PHPT) and controls, to determine risk of progression, and to develop a predictive model for progression to PHPT. This is a retrospective chart review of 232 patients at a tertiary medical center, comparing 75 controls, 73 patients with NHPT, and 84 with PHPT. NHPT was intermediate in biochemical profile between controls and PHPT with respect to cCa, iPTH, intraindividual coefficient of variant of cCa, phosphorus, and 25(OH)D. NHPT patients had an increased adjusted risk of urolithiasis (OR 5.34, 95%CI, 2.41-12.71, P < .001) and fragility fractures (OR 4.53, 95%CI, 1.63-14.84, P = .006) versus controls, after adjustment for age, sex, and BMI. Fewer NHPT compared with PHPTH patients achieved cure with parathyroidectomy (P = .001). NHPT more often had nonlocalizing imaging or polyglandular disease (P = .005). Parathyroidectomy improved biochemical but not BMD parameters in NHPT. Over a median follow-up of 4.23 (IQR 1.76-5.31) years, NHPT patients managed expectantly experienced no change in iPTH, and progression to PHPT occurred in 9%. An XGBoost model combining 6 factors for progression (mean index 2 iPTH, mean index 2 cCa, 24-h urinary calcium, age, 25(OH)D, and presence of urolithiasis) had an area under the curve 1.00 (95%CI, 1.00-1.00, P < .001) for predicting combined progression. NHPT is a mild variant of PHPT at intermediate risk of urolithiasis and fragility fractures. Cure was less often achieved with parathyroidectomy, which did not improve BMD parameters. Progression was infrequent with conservative management. Because only a minority progressed to PHPT, in addition to lower surgical success rates, we suggest conservative management for the majority of NHPT unless risk factors for progression are identified.

Incidental Normocalcemic Primary Hyperparathyroidism Presenting With Symptomatic Hypophosphatemia: A Case Report

Normocalcemic primary hyperparathyroidism (NHPT) is a newly defined variant of primary hyperparathyroidism (PHPT). It's defined by consistently normal total and ionised calcium levels with elevated parathyroid hormone in the absence of secondary causes of hyperparathyroidism in at least three consecutive times over a period of three to six months. Consensus whether the same criteria used to recommend surgery in PHPT should be used to recommend surgery in NHPT is still lacking. Even though PHPT is known to cause hypophosphatemia, serum phosphate is not relevant when diagnosing it or NHPT. No current guideline include any phosphate cutoff level to guide management or indicate surgery in PHPT or NHPT patients. Herein, we present a rare case of incidental NHPT presenting with symptomatic hypophosphatemia and managed surgically.

Comparative utility of preoperative imaging in normocalcemic versus hypercalcemic primary hyperparathyroidism

BACKGROUND

Normocalcemic primary hyperparathyroidism (PHPT) has been shown to benefit from parathyroidectomy. PHPT may be localized preoperatively with various imaging modalities, but the utility of preoperative imaging in normocalcemic PHPT compared to hypercalcemic PHPT is not well defined.

METHODS

Retrospective review was performed on all PHPT patients who underwent parathyroidectomy from 2001 to 2019. Patients were stratified into normocalcemic and hypercalcemic groups. Patient and outcomes data were analyzed.

RESULTS

All 2218 patients in this database were included. 433 patients had normocalcemic PHPT (19.5%) and 1785 had hypercalcemic PHPT (80.5%). Among normocalcemic patients, equivalent cure rates were seen between patients with preoperative imaging versus those without (100% vs 99%). No differences in postoperative complications were demonstrated except for a slightly increase in transient hypocalcemia in patients without imaging.

CONCLUSIONS

Normocalcemic PHPT patients had equivalent cure and similar complication rates with or without preoperative imaging compared to hypercalcemic patients. Routine localization studies in normocalcemic PHPT may be safely omitted in favor of exploration with intraoperative adjuncts by experienced surgeons.

Phenotypes of primary hyperparathyroidism: Does parathyroidectomy improve clinical outcomes for all?

BACKGROUND

Primary hyperparathyroidism consists of 3 biochemical phenotypes: classic, normocalcemic, and normohormonal primary hyperparathyroidism. The clinical outcomes of patients with normocalcemic primary hyperparathyroidism and normohormonal primary hyperparathyroidism are not well described.

METHOD

A retrospective review of patients who underwent parathyroidectomy at a single institution was performed. A logistical regression analysis of postoperative nephrolithiasis and highest percentage change in dual-energy x-ray absorptiometry scan comparison using Kruskal-Wallis test and Cox proportional hazard analysis of recurrence-free survival were performed.

RESULTS

A total of 421 patients were included (340 classic, 39 normocalcemic primary hyperparathyroidism, 42 normohormonal primary hyperparathyroidism). Median follow-up was 8.8 months (range 0-126). Higher rates of multigland disease were seen in normocalcemic primary hyperparathyroidism (64.1%) and normohormonal primary hyperparathyroidism (56.1%) compared to the classic (25.8%), P < .001. There were no differences in postoperative complications. The largest percentage increases in bone mineral density at the first postoperative dual-energy x-ray absorptiometry scan were higher for classic (mean ± SD, 6.4 ± 9.1) and normocalcemic primary hyperparathyroidism (4.8 ± 11.9) compared to normohormonal primary hyperparathyroidism, which remained stable (0.2 ± 14.2). Normocalcemic primary hyperparathyroidism were more likely to experience nephrolithiasis postoperatively, 6/13 (46.2%) compared to 11/68 (16.2%) classic, and 2/13 (15.4%) normohormonal primary hyperparathyroidism, P = .0429. Normocalcemic primary hyperparathyroidism was the only univariate predictor of postoperative nephrolithiasis recurrence (odds ratio [95% confidence interval] 4.44 [1.25-15.77], P = .029). Normocalcemic primary hyperparathyroidism was significantly associated with persistent disease with 6/32 (18.8%) compared to 1/36 (2.8%) and 3/252 (1.2%) in normohormonal primary hyperparathyroidism and classic (P < .001).

CONCLUSION

Three phenotypes of primary hyperparathyroidism are distinct clinical entities. Normocalcemic primary hyperparathyroidism had higher incidence of persistent disease and postoperative nephrolithiasis but demonstrated improvements in postoperative bone density. These data should inform preoperative discussions with patients with normocalcemic primary hyperparathyroidism and normohormonal primary hyperparathyroidism regarding postoperative expectations.

Normocalcemic primary hyperparathyroidism

Normocalcemic primary hyperparathyroidism (PHPT) is a newer phenotype of PHPT defined by elevated PTH concentrations in the setting of normal serum calcium levels. It is increasingly being diagnosed in the setting of evaluation for nephrolithiasis or metabolic bone diseases. It is important to demonstrate that PTH values remain consistently elevated and to measure ionized calcium levels to make the diagnosis. A diagnosis of normocalcemic disease is one of exclusion of secondary forms of hyperparathyroidism, including vitamin D deficiency, renal failure, medications, malabsorption, and hypercalciuria. Lack of rigorous diagnostic criteria and selection bias of the studied populations may explain the different rates of bone and renal complications. The natural history still remains unknown. Caution should be used in recommending surgery, unless clearly indicated. Here we will review the diagnostic features, epidemiology, clinical presentation, natural history, medical and surgical management of normocalcemic PHPT.

Elevated parathyroid hormone one year after kidney transplantation is an independent risk factor for graft loss even without hypercalcemia

Background

Hypercalcemic hyperparathyroidism has been associated with poor outcomes after kidney transplantation (KTx). However, the clinical implications of normocalcemic hyperparathyroidism after KTx are unclear. This retrospective cohort study attempted to identify these implications.

Methods

Normocalcemic recipients who underwent KTx between 2000 and 2016 without a history of parathyroidectomy were included in the study. Those who lost their graft within 1 year posttransplant were excluded. Normocalcemia was defined as total serum calcium levels of 8.5–10.5 mg/dL, while hyperparathyroidism was defined as when intact parathyroid hormone levels exceeded 80 pg/mL. The patients were divided into two groups based on the presence of hyperparathyroidism 1 year after KTx. The primary outcome was the risk of graft loss.

Results

Among the 892 consecutive patients, 493 did not have hyperparathyroidism (HPT-free group), and 399 had normocalcemic hyperparathyroidism (NC-HPT group). Ninety-five patients lost their grafts. Death-censored graft survival after KTx was significantly lower in the NC-HPT group than in the HPT-free group (96.7% vs. 99.6% after 5 years, respectively, P < 0.001). Cox hazard analysis revealed that normocalcemic hyperparathyroidism was an independent risk factor for graft loss (P = 0.002; hazard ratio, 1.94; 95% confidence interval, 1.27–2.98).

Conclusions

Normocalcemic hyperparathyroidism 1 year after KTx was an independent risk factor for death-censored graft loss. Early intervention of elevated parathyroid hormone levels may lead to better graft outcomes, even without overt hypercalcemia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02840-5.

Evaluation and Management of Elevated Parathyroid Hormone Levels in Normocalcemic Patients

Primary hyperparathyroidism is a common endocrine disorder. It used to present as a highly symptomatic disease before the advent of the multichannel autoanalyzer, now usually presenting as mild asymptomatic hypercalcemia. A newer presentation has been increasingly identified in the past two decades, normocalcemic primary hyperparathyroidism, presenting with elevated parathyroid hormone concentrations and consistently normal serum calcium. These patients are usually symptomatic, with parathyroid hormone levels measured in the evaluation for kidney stones or osteoporosis. It is important to exclude causes of secondary hyperparathyroidism. This review will focus on the evaluation and management of elevated parathyroid hormone levels in normocalcemic patients.

What happens to the bone structure after normocalcemic primary hyperparathyroidism surgery?

BACKGROUND

Bone disease in primary hyperparathyroidism is a clear indication for surgical treatment. However, it is not known whether surgery benefits hypercalcemic primary hyperparathyroidism and normocalcemic primary hyperparathyroidism equally. The aim of our study was to evaluate the bone changes in patients undergoing parathyroidectomy based on the biochemical profile 1 and 2 years after surgery.

METHODS

This prospective study included 87 consecutive patients diagnosed with primary hyperparathyroidism who underwent surgery between 2016 and 2018. Bone densitometry (1/3 distal radius, lumbar, and femur) and bone remodeling markers (osteocalcin, type 1 procollagen [P1NP], β-cross-linked telopeptide of type I collagen [BCTX]) were performed preoperatively and postoperatively. Postoperative changes in bone mineral density and bone markers were compared and evaluated according to the clinical characteristics and the individual biochemical profile.

RESULTS

One year after surgery, all patients showed an increase in bone mineral density at the lumbar site (mean, 0.029 g/cm²; range, 0.017-0.04; P < .001) and femur neck (mean, 0.025 g/cm²; range, 0.002-0.05; P < .001); however, there were no changes in the distal third of the radius (mean, -0.003 g/cm²; range, -0.008 to 0.002; P = NS). There were no significant differences when comparing normocalcemic primary hyperparathyroidism and hypercalcemic primary hyperparathyroidism. Serum osteocalcin (37 ± 17.41), P1NP (67.53 ± 31.81) and BCTX (0.64 ± 0.37) levels were elevated before surgery. One year after the surgery, we observed a significant decrease in P1NP (33.05 ± 13.16, P = .001), osteocalcin (15.80 ± 6.19, P = .001), and BCTX (0.26 ± 0.32, P < .001) levels.

CONCLUSION

Our findings indicate that parathyroidectomy has similar benefits for normocalcemic primary hyperparathyroidism and hypercalcemic primary hyperparathyroidism in terms of bone improvement. Although the most substantial improvement occurred during the first postoperative year in both groups, we consider that studies with longer follow-up are warranted.

A practical approach to normocalcemic primary hyperparathyroidism

Normocalcemic primary hyperparathyroidism is an entity on which several issues about its clinical management remains unclear. This is reflected in the main current guidelines, where there are no evidence-based specific recommendations. Through an exhaustive review of current literature, a clinical management algorithm for these patients is proposed. We consider the diagnosis criteria, the differential diagnosis, the clinical manifestations, and the treatment indications. When indicated, we also review the preoperative locations techniques and the surgical approach. Finally, when surgical treatment is not indicated, the patient is not a candidate to surgery or refuse surgical management, we review the medical treatment options and the follow-up schemes.

Primary hyperparathyroidism: Disease of diverse genetic, symptomatic, and biochemical phenotypes

Genetic, symptomatic, and biochemical heterogeneity of patients with primary hyperparathyroidism (PHPT) has become apparent in recent years. An in-depth, evidence-based review of the phenotypes of PHPT was conducted. This review was intended to provide the resulting information to surgeons who operate on patients with hyperparathyroidism. This review revealed that the once relatively clear distinction between familial and sporadic PHPT has become more challenging by the finding of various germline mutations in patients with seemingly sporadic PHPT. On the one hand, the genetic and clinical characteristics of some syndromes in which PHPT is an important component are now better understood. On the other hand, knowledge is emerging about novel syndromes, such as the rare multiple endocrine neoplasia type IV (MEN4), in which PHPT occurs frequently. It also revealed that, currently, the classical array of symptoms of PHPT is seen rarely upon initial presentation for evaluation. More common are nonspecific, nonclassical symptoms and signs of PHPT. In areas of the world where serum calcium levels are checked routinely, most patients today are "asymptomatic" and they are diagnosed after an incidental finding of hypercalcemia; however, some of them have subclinical involvement of bones and kidneys, which is demonstrated on radiographs, ultrasound, and modern imaging techniques. Last, the review points out that there are three distinct biochemical phenotypes of PHPT. The classical phenotype in which calcium and parathyroid hormone levels are both elevated, and other disease presentations in which the serum levels of calcium or intact parathyroid hormone are normal. Today several, distinct phenotypes of the disease can be identified, and they have implications in the diagnostic evaluation and treatment of patients, as well as possible screening of relatives.

Surgical management of MILD hyperparathyroidism

INTRODUCTION

There is no consensus for management of Mild primary hyperparathyroidism (MILD-pHP). Specific management has been suggested by some authors. We have compared the surgical management of the patients with MILD-pHP to those with Classic primary hyperparathyroidism (C-pHP) treated by surgery according to The Fourth International Workshop on pHP.

MATERIALS AND METHODS

Data of 173 patients who underwent a parathyroidectomy were reviewed and retrospectively analysed. Management of 32 patients with MILD-pHPT (18.5%) patients were compared to that of 141 (81.5%) patients with C-pHPT.

RESULTS

MILD-pHP group was more often discovered after non-fractured osteoporosis (21.9% vs 7.1%, p = 0.02) and surgery for chondrocalcinosis was more often carried out (6.3% vs 0%, p = 0.03) in the MILD-pHP group. A Mini-Invasive Parathyroidectomy (MIP) was carried out in 81.3% of cases, and 87.5% of patients had a single adenoma. The rate of multiglandular pathology was not different. Same day discharge was significantly higher in MILD-pHP group (37.5% vs 17.7%, p = 0.01). Success was obtained in 87.5% in the MILD-pHP group, there was no significant difference with the C-pHP group (92.9%, p = 0.48). There was no significant difference in the imaging performances. Imaging discordance was observed in 18.8% of cases in MILD-pHP and 33.6% in C-pHP (p = 0.38) without correlation with surgical failure.

CONCLUSION

This study suggests that, by selecting patients on the basis of concordant imaging and international recommendations, there is no difference in outcome between MILD-pHP and C-pHP treated surgically.

The value of parathyroid scintigraphy on lesion detection in patients with normocalcemic primary hyperparathyroidism

OBJECTIVE

Primary hyperparathyroidism (PHPT) is one of the most frequent endocrine diseases. Most of the patients with PHPT are asymptomatic, and only 20% of them become symptomatic with increasing levels of calcium. It has been reported that normocalcemic primary hyperparathyroidism (NPHPT) may be the incipient period of PHPT where calcium (Ca) levels are in normal range, and it may advance to overt PHPT. Early diagnosis of PHPT is important in order to prevent its complications. In this retrospective study, we aimed to evaluate the role of 99mTc-MIBI parathyroid scintigraphy on lesion detection in patients with NPHPT.

MATERIAL AND METHODS

The parathyroid scintigraphy database was reviewed retrospectively in patients with PHPT. 117 patients who underwent 99mTc-MIBI scintigraphy were recruited to the study. Serum calcium level above 10.5mg/dl was considered as hypercalcemia.

RESULTS

A total of 117 patients' (female/male:98/19) mean serum PTH levels (mean±SD) were 149±97 pg/ml in normocalcemic group (Ca:9.6±0.6mg/dL, n:38) and 189±135 pg/ml in hypercalcemic group (Ca:11.4±0.6mg/dL, n:79) (p:0.072). The sex and ages were not different between the scintigraphy positive and negative groups, but the lesion detection rates with parathyroid scintigraphy were 42% in normocalcemic group and 81% in hypercalcemic group (p<0.0001).

CONCLUSIONS

Several factors including serum Ca, the imaging protocol, existence of multiglandular disease, the size and MIBI biokinetics of the adenoma may influence lesion detectability in parathyroid scintigraphy. Although high serum Ca level is an important parameter in predicting its success, parathyroid scintigraphy remains a valuable diagnostic method even in patients with NPHPT.

How should we define cure after parathyroidectomy for normocalcemic primary hyperparathyroidism? A retrospective cohort study

Cure after surgery for normocalcemic primary hyperparathyroidism (NHPT) is defined as parathyroid hormone (PTH) normalization. However, an increase of PTH is frequently observed in cured patients with hypercalcemic primary hyperparathyroidism (HHPT). Therefore, this criterion must be redefined. A single-center retrospective study was performed including all patients who underwent surgery for Primary Hyperparathyroidism from 2013 to 2019. Cure rates of different types of hyperparathyroidism were analyzed. PTH reduction was studied as a possible criterion to define cure in patients with NHPT. One-hundred and eighty-six patients were included: 173 with HHPT and 13 with NHPT. After a mean follow-up of 33.4 months, 174 (93.6%) patients were considered cured. Cure was more frequent in the group of patients with HHPT (97.1% vs. 46.2%, p < 0.001). In the multivariate analysis, surgical failure was associated with NHPT and multiglandular disease. Forty-nine (30.1%) cured patients with HHPT had an increased PTH during the follow-up. When decline of PTH levels was studied in patients with HHPT to define cure, the area under curve was 0.92. A cut-off value of 40% in PTH reduction achieved a sensitivity and specificity of 83.4% and 80.0%. If cure was defined as a 40% reduction of PTH, cure rate in the group of patients with NHPT would increase to 69.2%. Patients with NHPT had a lower cure rate than patients with HHPT. A significant number of cured patients with HHPT had an increased PTH during follow-up. A 40% reduction in PTH levels is proposed as an alternative definition for cure in patients with NHPT.

Normocalcemic Primary Hyperparathyroidism: Need for a Standardized Clinical Approach

Since normocalcemic primary hyperparathyroidism (NHPT) was first defined at the Third International Workshop on the Management of Asymptomatic Primary Hyperparathyroidism in 2008, many papers have been published describing its prevalence and possible complications. Guidelines for the management of this condition are still lacking, and making the diagnosis requires fulfillment of strict criteria. Recent studies have shown that intermittent oscillations of serum calcium just below and slightly above the normal limits are very frequent, therefore challenging the assumption that serum calcium must be consistently normal to make the diagnosis. There is debate if these variations in serum calcium outside the normal range should be included under the rubric of NHPT or, rather, a milder form of classical primary hyperparathyroidism. Innovative approaches to define NHPT have been proposed that still need to be validated in prospective studies. Non-classical complications, especially cardiovascular complications, have been associated with NHPT, indicating that hyperparathyroidism may be a cardiovascular risk factor. New associations between parathyroid hormone (PTH) and several other comorbidities have also been reported from observational studies, suggesting that excessive PTH secretion might cause tissue dysfunction independent of serum calcium. Heterogeneous studies using different definitions of NHPT, however, make it difficult to draw definitive conclusions regarding the role of PTH excess when complications other than osteoporosis or kidney stones are described. This review will focus on clinical aspects and suggest an approach to NHPT.

Bones and Primary Hyperparathyroidism

Primary hyperparathyroidism (PHPT) is a disease caused by excessive and inappropriate secretion of parathyroid hormone resulting in hypercalcemia. It is usually diagnosed incidentally in the face of hypercalcemia, a complication such as osteoporosis or, more rarely, a renal complication with lithiasis. The clinical presentation reflects hypercalcemia and involves several organs, mainly the cardiovascular system, bones, and kidneys. However, most patients with PHPT are asymptomatic. The diagnosis is made based on laboratory tests. It is easy when serum calcium and parathyroid hormone levels are high, but difficult when one of these two values is normal. Normocalcemic PHPT can be diagnosed only after ruling out all causes of secondary hyperparathyroidism. Parathyroid imaging cannot diagnose it but guides the surgeon and rules out an associated thyroid abnormality. The reference treatment is surgery. The surgical indication is based on the presence or risk of complications, and it is the only treatment that prevents fractures. Pharmaceutical treatments have only limited effects on complications and are reserved for cases where surgery is contraindicated. After parathyroid surgery, the use of bisphosphonates must be avoided as they seem to interfere with the parathyroidectomy's fracture-preventing effects. If surgery is not indicated, a plan for monitoring laboratory values, bone density, and renal function will be established.

Normocalcemic and Normohormonal Primary Hyperparathyroidism: Laboratory Values and End-Organ Effects

OBJECTIVE

Variants of primary hyperparathyroidism (pHPT), described as normocalcemic (NC) and normohormonal (NH), can confuse the diagnosis of classic pHPT.

DATA SOURCES

A MEDLINE search was performed for variants of pHPT using the PubMed database (last queried October 2019).

REVIEW METHODS

The search was restricted to articles published after 1960 that were specific to humans. Studies were included in our analysis if laboratory values and incidence of end-organ involvement were reported for NCpHPT and NHpHPT variants. The search returned 189 articles; 27 additional studies were identified and included for a total of 216. Non-English-language studies were excluded. Abstracts were screened, full-text articles were then assessed, and 82 articles were excluded. Data were pooled using a random-effects model in studies that compared NC or NH pHPT to classic pHPT. Comparative laboratory values are presented.

CONCLUSION

This analysis compares NCpHPT and NHpHPT to classic pHPT. Nephrolithiasis was 21.7% (NCpHPT), 15.9% (classic pHPT), and 25.4% (NHpHPT). Decreased bone mineral density was 49.7% (NCpHPT), 39.7% (classic pHPT), and 40.3% (NHpHPT). Fractures in the NCpHPT group were not significantly different from the classic pHPT. Hypertension in the NCpHPT group was significantly less than classic pHPT (odds ratio, 0.59; 95% CI, 0.40-0.88).

IMPLICATIONS FOR CLINICAL PRACTICE

This information may serve to inform clinicians of the laboratory subtleties of these variants that are being seen with greater frequency in contemporary practice.

The effect of chronic kidney disease on intraoperative parathyroid hormone: A linear mixed model analysis

BACKGROUND

Reduced creatinine clearance is an indication for surgery in asymptomatic primary hyperparathyroidism, and a significant proportion of patients undergoing parathyroidectomy have chronic kidney disease. The purpose of this study was to evaluate the kinetics of intraoperative parathyroid hormone decline during parathyroidectomy in patients who have chronic kidney disease compared with those with who have normal renal function.

METHODS

This is a single-center, retrospective study of patients with primary hyperparathyroidism undergoing parathyroidectomy (n = 646). Patients were grouped based on estimated glomerular filtration rate greater than (normal renal function) or less than (chronic kidney disease) 60 mL/min/1.73m². All patients had intraoperative parathyroid hormone monitoring and ≥6-month postoperative serum studies to confirm surgical cure. Intraoperative parathyroid hormone kinetic curves were analyzed using a linear mixed model.

RESULTS

Despite similar pre-excision values, patients with chronic kidney disease had significantly higher intraoperative parathyroid hormone values at 5 minutes (76 vs 58 pg/mL, P = .02) and 10 minutes (54 vs 37 pg/mL, P = .004) postexcision. No significant difference was observed in whether patients met Miami criterion by 5 minutes (chronic kidney disease 71%, normal renal function 78%, P = .255) or by 10 minutes (chronic kidney disease 95%, normal renal function 96%, P = .751) postexcision. Using a linear mixed model, glomerular filtration rate did not have a significant effect on the change in intraoperative parathyroid hormone over time.

CONCLUSION

Patients with chronic kidney disease had significantly higher postexcision intraoperative parathyroid hormone levels. However, renal function did not affect the change in intraoperative parathyroid hormone over time, nor did renal function ultimately affect the likelihood of meeting the Miami criterion. Intraoperative parathyroid hormone monitoring remains useful in this population, although additional time points may be needed to observe normalization of values.

Normocalcaemic hyperparathyroidism and primary hyperparathyroidism: least significant change for adjusted serum calcium

INTRODUCTION

The least significant change (LSC) is a term used in individuals in order to evaluate whether one measurement has changed significantly from the previous one. It is widely used when assessing bone mineral density (BMD) scans. To the best of our knowledge, there no such estimate available in the literature for patients with disorders of calcium metabolism. Our aim was to provide an estimate of the least significant change for albumin-adjusted calcium in patients with normocalcaemic hyperparathyroidism (NPHPT) and primary hyperparathyroidism (PHPT).

METHODS

We used the within-subject standard deviatio calculated in a population of NPHPT and PHPT patients and multiplied it by 2.77.

RESULTS

The LSC for NPHPT and PHPT were found to be 0.25 and 0.24 mmol/L, respectively (1.00 and 0.96 mg/dL). In clinical practice, the value of 0.25 mmol/L could be used.

DISCUSSION

The least significant change given, could be used in two ways in these patients. First, it gives a range to which values are expected. This can provide some reassurance for the patient and the physician in cases of intermittent hypercalcaemia. Moreover, it can be a marker of whether an individual has an actual significant change of his calcium after parathyroid surgery.

Normocalcaemic primary hyperparathyroidism: what is the role of parathyroid surgery?

Primary hyperparathyroidism (PHPT) is classically associated with both an elevated or 'inappropriately normal' parathyroid hormone (PTH) level and raised serum calcium. However, in clinical practice, increasing numbers of patients present with raised PTH but normal serum calcium, renal function and vitamin D; this is known as normocalcaemic PHPT (nPHPT). Studies investigating the clinical presentation of this condition have shown that patients may present with hypertension, nephrolithiasis, impaired glucose tolerance, osteoporosis and fragility fractures. The prevalence of such complications in nPHPT is similar to that in classical hypercalcaemic PHPT (hPHPT). Although the National Institute for Health and Care Excellence (NICE) have developed guidelines for the management of PHPT generally, a consensus is yet to be reached on the optimal management of nPHPT specifically. A review of the literature on parathyroidectomy in the treatment of nPHPT revealed that nPHPT patients were more likely to present with multi-glandular disease and significantly less nPHPT patients had an intra-operative PTH fall of >50% compared with those with hPHPT. These findings demonstrate that patients with nPHPT are more likely to receive bilateral neck explorations and require remedial surgery compared with hPHPT patients. Following surgery, improvements in bone mineral density (BMD) and renal stones are generally observed in those with nPHPT. Where surgery is not possible, medical management with alendronate has been shown to be effective in nPHPT patients. Given the higher incidence of multi-gland disease and greater possibility of remedial surgery in nPHPT, careful consideration of risks and benefits should be made on an individualised basis and surgery should be performed by surgeons experienced in four gland exploration.

Normocalcaemic primary hyperparathyroidism: An update on diagnostic and management challenges

Normocalcaemic primary hyperparathyroidism is a condition that can present with intermittent hypercalcemia or may evolve into hypercalcemic primary hyperparathyroidism. This milder biochemical entity remains incompletely understood because of a lack of long-term health outcomes regarding both medical and surgical approaches to its management. Medical therapies have shown some efficacy. A limited number of studies have found that bisphosphonates increase bone mineral density, and calcimimetics may decrease the risk of nephrolithiasis in patients with normocalcaemic primary hyperparathyroidism. Studies have also described patient outcomes after applying the same surgical criteria used for patients with hypercalcaemic primary hyperparathyroidism to those with the normocalcaemic form of the disease. These studies suggest that parathyroid surgery appears to be effective in normalizing elevated serum parathyroid hormone concentrations and decreasing adverse renal and skeletal outcomes in patients with normocalcaemic hyperparathyroidism. Given the available data and overall lack of consensus regarding the optimal management of these patients, a reasonable approach is to tailor treatment to the individual patient by considering their risk factors for new or accelerated bone loss, kidney stones, diminished quality of life, and cardiovascular disease.

Normocalcemic primary hyperparathyroidism: an update

Normocalcemic primary hyperparathyroidism (NPHPT) is diagnosed in the setting of elevated PTH concentrations with consistently normal albumin-adjusted and ionized serum calcium levels, in absence of secondary causes for elevated PTH concentrations. In order to confirm persistence of the hyperparathyroid state, PTH levels should be elevated on at least two occasions over a 3 to 6 months period. The prevalence of NPHPT depends on the population studied. Data from different studies are often not comparable; indeed, different criteria have been used to exclude secondary hyperparathyroidism. Notwithstanding such limits, the prevalence of NPHPT in studies including ionized calcium dosage was between 0.5% and 0.7%. Available data suggest that patients with NPHPT are likely to have more skeletal, kidney and metabolic complications compared to healthy subjects, but almost all studies suffer from possible misclassification of patients due to lack of ionized calcium dosage. The management of NPHPT is controversial in part due to lack of solid data about the natural history. However, surgical treatment is currently performed more frequently than in the past, although studies do not show, so far, a clear benefit from intervention.

Normocalcemic Hyperparathyroidism: A Heterogeneous Disorder Often Misdiagnosed?

Normocalcemic primary hyperparathyroidism (NHPT) was first described over 10 years ago, but uncertainties still remain about its definition, prevalence, and rates of complications. As a result, consensus management guidelines for this condition have not yet been published. Several hypotheses have been proposed for the pathophysiology of NHPT, but it may be a heterogeneous disorder with multiple causes, rather than a single etiology that explains this biochemical phenotype. A common clinical concern is whether NHPT should be treated surgically when complications are already present at first recognition of the disorder, rather than following patients clinically over time. The literature on NHPT is based mostly on larger studies of population‐based cohorts and smaller studies from referral centers. Lack of rigorous diagnostic criteria and selection bias inherent in populations seen at tertiary referral centers may explain the heterogeneity of reported rates of bone and renal complications in relation to consistently mild laboratory alterations. Unresolved questions remain about the significance of NHPT when it is diagnosed biochemically without evident bone or kidney complications. Moreover, its natural history remains to be elucidated because a proportion of what is classified as NHPT may revert to normal spontaneously, thus revealing previously unrecognized secondary hyperparathyroidism. These issues indicate that caution should be used in recommending surgery for NHPT. This review will focus on recent issues regarding the pathophysiology, evaluation, and management of NHPT. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Normocalcemic Hyperparathyroidism: Study of its Prevalence and Natural History

CONTEXT

Normocalcemic hyperparathyroidism (NPHPT) is characterized by persistently normal calcium levels and elevated parathyroid hormone (PTH) values, after excluding other causes of secondary hyperparathyroidism. The prevalence of the disease varies greatly and the data on the natural history of this disease are sparse and inconclusive.

OBJECTIVES

The objectives of this study are to describe the prevalence of NPHPT and its natural history in a referral population and to compare the variability of serum calcium with a group of patients with primary hyperparathyroidism (PHPT).

DESIGN

A retrospective study was conducted over 5 years.

SETTING

The setting for this study was a metabolic bone referral center.

PATIENTS

A total of 6280 patients were referred for a bone mineral density measurement (BMD).

MAIN OUTCOME MEASURES

The prevalence and natural history of NPHPT and variability of calcium were the main outcome measures.

RESULTS

We identified NPHPT patients using data from the day of the BMD measurement. We excluded patients with low estimated glomerular filtration rate (eGFR) or vitamin D, or with no measurements available. Based on the evaluation of their medical files, we identified 11 patients with NPHPT (prevalence 0.18%). Only 4 patients had consistent normocalcemia throughout their follow-up, with only 2 also having consistently high PTH. None had consistently normal eGFR or vitamin D.Intermittent hypercalcemia was present in 7 of the 11 NPHPT patients. The mean adjusted calcium was found to be significantly lower in the NPHPT group compared with the PHPT group but higher than the control group. PTH was similar for NPHPT and PHPT. These 2 groups had similar variability in serum calcium.

CONCLUSIONS

NPHPT patients often have episodes of hypercalcemia. We believe that NPHPT is a mild form of PHPT.

Comparative prospective study on the presentation of normocalcemic primary hyperparathyroidism. Is it more aggressive than the hypercalcemic form?

BACKGROUND

Some patients with primary hyperparathyroidism (PHPT) have an elevated PTH that does not always correlate with high blood calcium levels. We aimed to compare the clinical presentation between normocalcaemic and hypercalcaemic forms using ionized calcium levels as an inclusion criterion.

METHODS

We included all patients referred for surgery for PHPT between January 2015 and December 2017. Patients were divided into 2 groups (hypercalcaemic (hPHTP)/normocalcaemic (nPHPT)).

RESULTS

104 patients were included.64% of the patients who were initially classified as normocalcaemic had high ionized calcium levels. There were no differences between groups except in terms of bone resorption parameters:patients with hypercalcaemia had higher osteocalcin (37.4vs23.5 ng/mL,P = .02), collagen amino-terminal propeptide (73.5vs49.2 ng/mL,P = .005), and beta-CTX levels (0.68vs0.38 ng/mL,P = .001). Bone involvement as measured by densitometry was similar.

CONCLUSSIONS

When these patients' diagnosis and classification is accurate, their clinical presentation and symptoms are similar to those of the classical form. Since the only difference is in terms of bone resorption parameters, in most cases it seems to be an attenuated form or even similar to the classical presentation. The improvement in diagnostic sensitivity supports the use of ionized calcium levels in patients suspected to have nPHPT.

Primary hyperparathyroidism: should surgery be performed on all patients? Current evidence and residual uncertainties

Primary hyperparathyroidism (pHPT) is the third most common endocrine disease and is characterized by hypercalcaemia and elevated or inappropriately 'normal' levels of the parathyroid hormone (PTH). The main target organs of PTH are the skeletal system and the kidneys. Before the 1970s, pHPT was a rarely detected disease associated with notable morbidity and premature mortality. Introduction of biochemical screening, allowing for a wide range of indications, has contributed to the detection of the full spectrum of the disease. A new entity with an isolated elevation of PTH, normocalcaemic HP, has emerged and is currently being explored. The highest incidence of pHPT, 3-5%, is observed amongst women, and the prevalence increases with age. The female-to-male ratio is 3-4 : 1 except in younger patients where distribution is equal and known hereditary causes account for approximately 10% of the cases. In the last few decades, it has become evident that fewer patients than previously believed are truly asymptomatic. The cause of pHPT is often a benign tumour, a parathyroid adenoma, and the only definite treatment is parathyroidectomy (PTX). No medical treatment, single or combined, can achieve a curing of pHPT. Recent data indicate that PTX, despite being proven to be cost-effective compared to conservative treatment, is underutilized, especially in elderly pHPT patients. The decision of PTX should always be based on a safe diagnosis, and the potential benefits of curative treatment should not be outweighed by the risks of surgery or anaesthesia.

Management of normocalcemic primary hyperparathyroidism

Traditional hypercalcemic primary hyperparathyroidism is a common endocrine disease. Patients with a history of nephrolithiasis or a suspected metabolic bone disease are increasingly being identified with elevated PTH concentrations in the setting of consistently normal serum and ionized calcium concentrations. In the absence of secondary causes of hyperparathyroidism, a diagnosis of normocalcemic primary hyperparathyroidism is reasonable. As most cohorts described in the literature are from referral populations, involvement of the skeleton and the kidneys is common, two traditional target organs of primary hyperparathyroidism. Data from small cohorts show patients with normocalcemic disease respond similarly to hypercalcemic primary hyperparathyroidism with regard to medical and surgical approaches. In normocalcemic patients, multiglandular disease may be more common. In this article, we review the available literature on the epidemiology, diagnosis, clinical features, medical and surgical management of this newer phenotype of primary hyperparathyroidism.

Primary Hyperparathyroidism

Background

Primary hyperparathyroidism (PHPT), the most common cause of hypercalcemia, is most often identified in postmenopausal women. The clinical presentation of PHPT has evolved over the past 40 years to include three distinct clinical phenotypes, each of which has been studied in detail and has led to evolving concepts about target organ involvement, natural history, and management.

Methods

In the present review, I provide an evidence-based summary of this disorder as it has been studied worldwide, citing key concepts and data that have helped to shape our concepts about this disease.

Results

PHPT is now recognized to include three clinical phenotypes: overt target organ involvement, mild asymptomatic hypercalcemia, and high PTH levels with persistently normal albumin-corrected and ionized serum calcium values. The factors that determine which of these clinical presentations is more likely to predominate in a given country include the extent to which biochemical screening is used, vitamin D deficiency is present, and whether parathyroid hormone levels are routinely measured in the evaluation of low bone density or frank osteoporosis. Guidelines for parathyroidectomy apply to all three clinical forms of the disease. If surgical guidelines are not met, parathyroidectomy can also be an appropriate option if no medical contraindications are present. If either the serum calcium or bone mineral density is of concern and surgery is not an option, pharmacological approaches are available and effective.

Conclusions

Advances in our knowledge of PHPT have guided new concepts in diagnosis and management.