How to manage an isolated elevated PTH?

Evaluation of the thiazide challenge test to differentiate primary from hypercalciuria-related hyperparathyroidism

CONTEXT

treatment of primary hyperparathyroidism (PHPT) and secondary hyperparathyroidism due to idiopathic hypercalciuria (SHPT-IH) is markedly different. Robust diagnostic tools to differentiate between both entities are however lacking.

OBJECTIVE

evaluate the thiazide challenge test (TCT) in clinical practice, its aid in clinical decision making, evaluate the accuracy (sensitivity, specificity) and potentially useful parameters of the TCT.

DESIGN

monocentric observational retrospective cohort study from January 2017 to November 2023.

SETTING

outpatient, Ghent University Hospital (Belgium).

PATIENTS

25 adult patients with hypercalciuria, elevated parathyroid hormone (PTH), and high-normal or elevated serum calcium that underwent a TCT.

INTERVENTION

TCT.

OUTCOME MEASURES

serum, urinary biochemical parameters before and after testing, clinical and imaging outcomes, treatment, and follow-up.

RESULTS

patients with a TCT-based working diagnosis of PHPT show greater increases in albumin-adjusted calcium and total serum calcium concentration than patients with SHPT-IH (+0,11 ± 0,10 vs. + 0,0071 ± 0,10mmol/l; p = 0,025 and +0,14 ± 0,12 vs. + 0,012 ± 0,15mmol/l; p = 0,024 respectively). The TCT-based working diagnosis of PHPT has a sensitivity of 81,8%, a specificity of 77,8% and a likelihood ratio of 3,68 of estimating a correct final diagnosis.Urinary calcium excretion, PTH, calcium-phosphorous ratio, PTH-inhibition rate, and parathyroid function index do not differ significantly in patients with PHPT compared to those with SHPT-IH.

CONCLUSION

the TCT aids in discriminating patients with PHPT from those with SHPT-IH based on a rise in serum calcium. Other parameters are not different between both groups. Larger prospective trials are necessary to further define the diagnostic potential of the TCT, its most appropriate biochemical outcome variables, and decision cut-offs.

Comparison of normocalcemic versus hypercalcemic primary hyperparathyroidism in a hypercalciuric renal stone population

CONTEXT

Primary hyperparathyroidism (PHPT) is commonly diagnosed in the setting of hypercalcemia, whereas normocalcemic primary hyperparathyroidism (NHPT) may be misdiagnosed.

OBJECTIVE

Our objective was to compare hypercalcemic hyperparathyroidism (HPHPT) versus NHPT hypercalciuric renal stone patients.

DESIGN AND SETTING

We took advantage of a routine calcium load test performed in hypercalciuric renal stone patients to assess retrospectively among PHPT patients, prevalence and characteristics of NHPT and HPHPT under a calcium restricted diet.

RESULTS

Among 1671 hypercalciuric patients included, 91 patients have a final diagnosis of PHPT(post load ionized calcium (iCa)>1.31 mmol/L and PTH>30 pg/ml). Prevalence of NHPT is 40% of all PHPT, however according to total serum calcium 4/35 NHPT and 7/56 HPHPT would have been misclassified in the other group. 18/35 NHPT and 40/56 HPHPT underwent parathyroidectomy. No significant characteristics related to parathyroid weight, stone composition or bone remodeling biomarkers is detected between groups. Whereas iCa is higher in HPHPT in fasting state and after calcium load, we found no difference for calcium diet, 24-hour calciuria, or calcitriol. Of notice, renal calcium excretion (FECa) post load increases by 303% in NHPT but only 176% in HPHPT (p=0.01) likely explained by a lesser PTH decrease (p=0.02). However, a strong negative association (p<0.0001) detected between pooled pre and post load iCa and PTH only in NHPT group suggests a persistent efficient PTH-CaSR control within parathyroid glands in this group.

CONCLUSION

Our data show the relevance of dynamic tests to unmask NHPT in hypercalciuric renal stone patients.

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.

The Calcium Loading Test in Primary Hyperparathyroidism – Does it Provide Useful Information?

Objective: to describe the results from intravenous calcium loads in patients with suspected PHPT.

Methods: This was a retrospective cross-sectional study with inpatients’ data review. Baseline serum calcium, phosphates, magnesium, creatinine, alkaline phosphatase, beta-crosslinks were recorded. The calcium loading had been performed after an overnight fasting. Calcium gluconate 0.25 mmol/kg body weight (10 mg/kg) dissolved in 0.9% Sodium Chloride was infused intravenously for 3 hours. Blood samples for total serum calcium, phosphates and iPTH were drawn before and up to 60 minutes after the calcium load. The intact parathyroid hormone (iPTH) and 25(OH)-vitamin D were determined by electro-hemi-luminescence (Elecsys, Roche Diagnostics). The PTH inhibition rate in % (PTH-IR), the calcium increment, the ratio R (ΔPTH/ΔCalcium) and the product P (calcium X PTH at test end) were calculated.

Results: 23 patients with PHPT had complete data from calcium loading tests. The PTH suppression was < 30% in 17.4% of the participants, 30% to 50% – in 21.7% and > 50% in the remaining 60.9%. One patient displayed PTH suppression > 75%. The Ratio R was < 4.0 in all but one patient. Product P was above 1100 mg/dl x pg/ml in 9 participants (39.1%). Sixteen patients (69.6%) had positive localization results from US or SPECT-CT. The level of PTH suppression was not related to any parameter except the volume of the suspected lesion.

Conclusion: The calcium loading test was unable to differentiate the forms of PHPT. It did not add great value in the diagnostic work-up of PHPT.

Calcium Challenge to Confirm Secondary Hyperparathyroidism due to Decreased Calcium Intake

OBJECTIVE

Secondary hyperparathyroidism commonly occurs in the setting of mid-to low-normal serum calcium levels, often in the setting of chronic kidney disease, phosphate loading, vitamin D deficiency, or insufficient calcium intake or absorption. We are reporting nine patients who had adequate kidney function [eGFR (estimated glomerular filtration rate) >60 mL/min/1.73 m²] and normal 25-hydroxy vitamin D level (≥30 ng/dL) whose secondary hyperparathyroidism resolved after starting adequate oral calcium intake.

METHODS

Our retrospective case series included eight women and a man, aged (mean ± standard deviation) 69.0 ± 12.2 years. Initial intact parathyroid hormone (iPTH) level was 80.6 ± 13.4 pg/mL (reference range [ref]: 10-65 pg/mL), corrected serum calcium 9.2 ± 0.2 mg/dL (ref: 8.5-10.5 mg/dL), serum phosphate 3.6 ± 0.4 mg/dL (ref: 2.5-4.9 mg/dL), 25-hydroxy vitamin D 42.2 ± 10.5 mg/dL (ref: 20-50 ng/mL), and eGFR 72.6 ± 14.4 ml/min/1.73 m². Patients were treated clinically with oral calcium 600 mg twice daily.

RESULTS

iPTH was retested after a mean duration of 17.6 ± 12.7 days of calcium supplementation, decreased to 51.0 ± 10.6 pg/mL, with all patients achieving iPTH in the normal range with normocalcemia, consistent with the hyperparathyroidism being due to insufficient calcium intake or absorption. All patients were normocalcemic after supplementation.

CONCLUSION

Secondary hyperparathyroidism can result from insufficient oral calcium intake. Calcium challenge is an efficacious cost-effective tool in confirming and treating secondary hyperparathyroidism in the setting of normal vitamin D stores and kidney function.

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.

Primary Hyperparathyroidism – A Contemporary Picture Based on 100 Patients from the Last Decade

Primary hyperparathyroidism (PHPT) is an endocrine disease, the clinical picture of which has slowly shifted to milder and asymptomatic forms during the last decades.

Objective

to describe the clinical presentation and the main laboratory and imaging findings in a group of patients with PHPT diagnosed during the last 10 years.

Materials and Methods

This was a retrospective cross-sectional study with data review from the database of a tertiary endocrine clinic from the last 10 years. Secondary causes for elevated PTH were excluded. The major clinical symptoms and signs of hypercalcemia/HPT were reviewed as well as concomitant diseases and medications. Serum calcium (total, albumin-corrected and ionized; sCa, corrCa, iCa+), phosphates (P), magnesium, creatinine, alkaline phosphatase, beta-crosslinks were measured. The intact parathyroid hormone (iPTH) and 25(OH)-vitamin D were determined by electro-hemi-luminescence (Elecsys, Roche Diagnostics). 24-hour urinary probes for calcium and phosphate were collected. Neck ultrasound (US) was used as the localization study of choice. Almost half of the participants underwent fine-needle aspiration biopsy (FNAB) with cytology and needle-washouts for iPTH. One fourth of the patients were assessed by Single-Photon Emission Tomography (SPECT-CT). Data on bone density (from DXA), fractures and renal stones (from renal US) were collected.

Results

One hundred patients met the study criteria – 95 were women. Most of them were in their 5th and 6th decades. The median corrected sCa was 2.73 mmol/l, iCa+ – 1.39 mmol/l, P – 0.88 mmol/l, iPTH – 14.5 pmol/l and 25(OH)D – 54.0 nmol/l. Normal sCa was registered in 20 participants (20%), while normal sP – in 67.0%. The neck US located single lesions (parathyroid adenoma) in 81% – behind or below the left inferior pole of the thyroid gland in 33 cases (33%) and contra-laterally in another 33%. FNAB of the suspicious lesion had been performed in 51% of the study subjects. The cytology confirmed the presence of parathyroid cells in 22 cases (43.1%), Bethesda II thyroid nodules in 21 cases (41.2%), Bethesda III nodules in 2 cases (3.9%) and insufficient samples (Bethesda I) in 5 cases (9.8%). SPECT-CT from 27 patients identified a suspicious left parathyroid in 11 cases, a right one – in 6 cases, as well as three ectopic locations. BMD data were available in 66 female patients and showed a higher prevalence of osteoporosis than in the general age-matched population; fractures, however, were not more frequent. Data from renal ultrasound were available in 77% and revealed chronic pyelonephritis without stones in 8 patients and renal stone disease – in 37 patients.

Conclusion

To our knowledge, this study is the first of its kind in our country during the last two decades. Mild to moderate hypercalcemia was very common, although most patients were oligoor asymptomatic. Renal and bone involvement were surprisingly frequent, with reduced eGFR and low bone mass being more prevalent than in the general population. The most typical location was a single parathyroid lesion within the lower glands. The use of SPECT-CT seems to decline and is replaced by US-guided FNAB with needle washout measurements of iPTH and cytological examination. Although the general picture of PHPT is shifting towards milder and asymptomatic (and probably earlier) forms of the disease, the classical clinical presentation can still be found in everyday practice.

A case of insulinoma diagnosed postpartum with hypoglycemic symptoms that were masked during pregnancy

The diagnosis of insulinoma in perinatal women can be difficult, as hypoglycemic symptoms may be masked by pregnancy-associated insulin resistance. In addition, when multiple insulinomas are observed, it is necessary to consider the possibility not only of MEN1, but also of insulinomatosis.

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.

Investigating patients with normocalcemic hyperparathyroidism: When is a parathyroid scintigraphy indicated?

In clinical practice, physicians often encounter patients with persistent elevated serum parathyroid hormone levels and normal serum calcium levels, a state known as normocalcemic hyperparathyroidism (NHPT). The investigation of NHPT cases can lead to unnecessary use of parathyroid scintigraphy (PS) and consequently unnecessary health-care costs. In this clinical review, the most common causes of NHPT and the possible indications for PS performance in such cases are mainly presented and discussed.

Normocalcaemic primary hyperparathyroidism: a pragmatic approach

It is well recognised that over the past three to four decades the incidence of asymptomatic primary hyperparathyroidism has increased significantly. However, more recently this pattern has further evolved into a presentation with normocalcaemia and raised parathyroid hormone (PTH) level without the presence of a recognised stimulus for its rise, in the form of vitamin D deficiency or renal impairment. A diagnostic label of normocalcaemic hyperparathyroidism (NPHPT) has been given to this phenotype and in most such individuals, the initial PTH measurement is driven by the presence of metabolic bone disease. The reported prevalence, degree of end-organ involvement and the rate of progression vary considerably and are related to patients studied and the biochemical cut-offs used in its definition. A majority of patients are diagnosed during assessment of metabolic bone disease of varying degrees. Once the diagnosis is confirmed by excluding confounding factors, the patient should undergo full assessment of end-organ involvement, which is the main determinant of further therapeutic decisions. Surgery, with prior localisation, is considered in patients with significant end-organ involvement in keeping with the guidance for hypercalcaemic patients. If a patient does not meet these criteria, annual clinical and biochemical surveillance is recommended to identify progression to hypercalcaemia or worsening end-organ involvement. It is less clear if patients identified during 'routine' requests for evaluation of unrelated symptoms require similar close monitoring. In conclusion, in this review on NPHPT we focus on its definition, planning of further investigations, selection of patients for intervention and devising an appropriate follow-up strategy.

How the reference values for serum parathyroid hormone concentration are (or should be) established?

Well-validated reference values are necessary for a correct interpretation of a serum PTH concentration. Establishing PTH reference values needs recruiting a large reference population. Exclusion criteria for this population can be defined as any situation possibly inducing an increase or a decrease in PTH concentration. As recommended in the recent guidelines on the diagnosis and management of asymptomatic primary hyperparathyroidism, PTH reference values should be established in vitamin D-replete subjects with a normal renal function with possible stratification according to various factors such as age, gender, menopausal status, body mass index, and race. A consensus about analytical/pre-analytical aspects of PTH measurement is also needed with special emphasis on the nature of the sample (plasma or serum), the time and the fasting/non-fasting status of the blood sample. Our opinion is that blood sample for PTH measurement should be obtained in the morning after an overnight fast. Furthermore, despite longer stability of the PTH molecule in EDTA plasma, we prefer serum as it allows to measure calcium, a prerequisite for a correct interpretation of a PTH concentration, on the same sample. Once a consensus is reached, we believe an important international multicentre work should be performed to recruit a very extensive reference population of apparently healthy vitamin D-replete subjects with a normal renal function in order to establish the PTH normative data. Due to the huge inter-method variability in PTH measurement, a sufficient quantity of blood sample should be obtained to allow measurement with as many PTH kits as possible.

Clinicopathological correlates of hyperparathyroidism

Hyperparathyroidism is a common endocrine disorder with potential complications on the skeletal, renal, neurocognitive and cardiovascular systems. While most cases (95%) occur sporadically, about 5% are associated with a hereditary syndrome: multiple endocrine neoplasia syndromes (MEN-1, MEN-2A, MEN-4), hyperparathyroidism-jaw tumour syndrome (HPT-JT), familial hypocalciuric hypercalcaemia (FHH-1, FHH-2, FHH-3), familial hypercalciuric hypercalcaemia, neonatal severe hyperparathyroidism and isolated familial hyperparathyroidism. Recently, molecular mechanisms underlying possible tumour suppressor genes (MEN1, CDC73/HRPT2, CDKIs, APC, SFRPs, GSK3β, RASSF1A, HIC1, RIZ1, WT1, CaSR, GNA11, AP2S1) and proto-oncogenes (CCND1/PRAD1, RET, ZFX, CTNNB1, EZH2) have been uncovered in the pathogenesis of hyperparathyroidism. While bi-allelic inactivation of CDC73/HRPT2 seems unique to parathyroid malignancy, aberrant activation of cyclin D1 and Wnt/β-catenin signalling has been reported in benign and malignant parathyroid tumours. Clinicopathological correlates of primary hyperparathyroidism include parathyroid adenoma (80-85%), hyperplasia (10-15%) and carcinoma (<1-5%). Secondary hyperparathyroidism generally presents with diffuse parathyroid hyperplasia, whereas tertiary hyperparathyroidism reflects the emergence of autonomous parathyroid hormone (PTH)-producing neoplasm(s) from secondary parathyroid hyperplasia. Surgical resection of abnormal parathyroid tissue remains the only curative treatment in primary hyperparathyroidism, and parathyroidectomy specimens are frequently encountered in this setting. Clinical and biochemical features, including intraoperative PTH levels, number, weight and size of the affected parathyroid gland(s), are crucial parameters to consider when rendering an accurate diagnosis of parathyroid proliferations. This review provides an update on the expanding knowledge of hyperparathyroidism and highlights the clinicopathological correlations of this prevalent disease.