Diagnosis of normocalcemic hyperparathyroidism by oral calcium loading test

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.

Metabolic Evaluation: Place of the Calcium Load Test: How, When, For Whom, and Why?

Most human urinary stones are calcium-based and are often associated with hypercalciuria. A simple test described in 1975 by Pak et al allows for pathogenic classification of hypercalciuria: the calcium load test (CLT). The CLT explores calcium homeostasis after a low-calcium diet and then a calcium load (typically oral administration of 1 g of elemental calcium). Only simple laboratory equipment is required. Inadequate calcium excretion after a calcium-free diet or a calcium load is suggestive of resorptive or absorptive hypercalciuria, respectively. The CLT is particularly valuable in diagnosing primary hyperparathyroidism, even in most early stages of this disease. PATIENT SUMMARY: Kidney stone formation can be linked to calcium metabolism. When high calcium levels are found in urine despite adequate diet changes, a calcium load test may help to understand the underlying mechanisms. Urine and blood levels are explored during a low-calcium diet phase, and after a calcium load phase in the test. The calcium load test is particularly advantageous for revealing abnormally high function of the parathyroid gland, which is called hyperparathyroidism.

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

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

A step towards cinacalcet testing for the diagnosis of primary hyperparathyroidism: comparison with the standardized intravenous calcium loading. A pilot study

OBJECTIVE

A calcium load to suppress parathyroid hormone (PTH) secretion can help to perform the diagnosis in some case of primary hyperparathyroidism (PHPT) with atypical presentation. A similar test with calcimimetic, which avoids hypercalcaemia, would be of interest. Our proof of concept study was conducted to compare firstly the results of a single-dose cinacalcet testing with those of the standardized short-time calcium load in healthy control (HC) and secondly the results of the single-dose cinacalcet testing in HC and in PHPT.

METHODS

Twelve HCs received in a random order, at a 2-week interval, either 0·33 mmol/kg calcium gluconate intravenously for 3 h, or a single oral dose of 30 mg or 60 mg cinacalcet. Twelve PHPTs received 30 mg cinacalcet and twelve other PHPTs 60 mg cinacalcet orally. Calcaemia and serum PTH levels were measured basally and then hourly for 6 h.

RESULTS

In HC, plasma calcium did not significantly change after cinacalcet intake, whereas calcaemia rose up to 3·47 ± 0·05 mmol/l (mean ± SEM) at the end of the calcium load. PTH dropped from basal level to a similar extend (≥80%) with 60 mg cinacalcet and calcium load, whereas the decrease was significantly lesser (P < 0·01) with 30 mg cinacalcet. In PHPT, serum PTH levels dropped by 44·8 ± 6·9% and 58·2 ± 5·3% 1 h after the respective intake of 30 and 60 mg cinacalcet. One hour after the oral intake of 60 mg cinacalcet, serum PTH levels were <8 ng/l in HC and ≥8 ng/l in PHPT.

CONCLUSION

Sixty milligrams of cinacalcet provides similar results as the standardized calcium load test; PHPT patients have a lower response to 60 mg cinacalcet than HC.

[Normocalcemic primary hyperparathyroidism: a growing problem]

Normocalcemic primary hyperparathyroidism is at present one of the most common reasons for consultation in bone metabolism units. It is characterized by increased levels of intact parathyroid hormone in the presence of normal serum calcium (total and ionized) in generally asymptomatic individuals. The differential diagnosis should be considered in all situations that occur with secondary hyperparathyroidism. Its natural history is not well known, and it does not always progress to hypercalcemia. As a recently recognized entity, there are still no specific recommendations for its management. In this review we discuss some aspects of this entity, emphasizing the importance of a proper laboratory diagnosis, assessing possible signs or symptoms associated such as kidney stones or osteoporosis, which can help the clinician to take a conservative or interventionist attitude.

Primary hyperparathyroidism: role of the preoperative oral calcium loading test in the differential diagnosis between adenoma and hyperplasia

Whereas the sensitivity of the membrane calcium receptors is decreased in parathyroid adenoma, extracellular calcium may reduce parathyroid hormone (PTH) secretion through the protein kinase C pathway in parathyroid hyperplasia. The aim of this study was to determine the role of a preoperative oral calcium loading test in the differential diagnosis between adenoma and hyperplasia. Twenty-two subjects with adenoma (group A, age +/- standard error 56 +/-2 years, female/male 15/7), 10 individuals with hyperplasia (group H, age 54 +/-3, female/male 8/2), and 32 age and gender pair-matched controls (group C) underwent the test. Calcium and PTH were measured before and 60, 120, and 180 min after oral administration of 1 g of calcium (as gluconolactate). Product P was defined as minimal PTH concentration (pg/mL) x maximal calcium concentration (mg/dL) during the test. Ratio R was defined as relative PTH decline/relative calcium increase. The PTH decline during the test in group H was comparable to that of the controls. PTH decline <30%, Product P > 1,100, and Ratio R < 4 diagnosed adenoma with specificity of 100%, 90%, and 100%, respectively. PTH decline >60% diagnosed hyperplasia with specificity of 100%. The total accuracy of the test (65%) was comparable to that of technetium-99 m sestamibi scintigraphy (66%) and better than that of ultrasonography (58%). The test may discriminate patients with sporadic diffuse hyperplasia from individuals with solitary adenoma in cases of primary hyperparathyroidism with an indication for surgery.

Normocalcemic primary hyperparathyroidism in patients with recurrent kidney stones: pathological analysis of parathyroid glands

The lack of overt elevation of serum calcium concentration in some patients suffering from primary hyperparathyroidism is an intriguing clinical phenomenon. Previous studies have substantiated abnormal parathyroid tissue in these patients, but the extent and mode of derangements remained largely undefined. The parathyroid tissues from patients of normocalcemic primary hyperparathyroidism (NCPHPT) and those having normal parathyroid glands, hypercalcemic primary hyperplasia, secondary hyperplasia, and adenoma were compared by undertaking quantitative immunohistochemistry analysis on tissue microarray. The statistic results suggested that the parathyroid tissue of NCPHPT approximates more to normal gland than to its counterpart in other groups of parathyroid proliferative diseases in terms of the lack of significant alterations of calcium-sensing receptor (CaSR), chromogranin A (CGA), parathyroid hormone (PTH), and proliferation index (Ki67). On the other hand, the depressed vitamin D receptor (VitDR) and elevated cyclin D1 (CyD1) of NCPHPT indicated the inherent functional abnormalities in parathyroid cells. Our results imply that inherent functional disengagement may exist between CaSR and CyD1 or between CaSR and VitDR or both in parathyroid cells of symptomatic NCPHPT. Lack of enhanced release of CGA and PTH and discordance between proliferative activity and CyD1 expression in parathyroid cells may further hinder the development of hypercalcemia.

Association between primary hyperparathyroidism and increased body weight: a meta-analysis

Although primary hyperparathyroidism is frequently asymptomatic, it has been associated with an increased prevalence of hypertension, insulin resistance, dyslipidemia, cardiovascular mortality, and cancer. Previously we reported that patients with primary hyperparathyroidism are heavier than age-matched controls. Increased body weight could contribute to the association between primary hyperparathyroidism and these extraskeletal complications. We searched MEDLINE for English language studies published between 1975 and 2003 that reported body weight or body mass index in subjects with primary hyperparathyroidism and a healthy age- and sex-comparable eucalcemic control group. Seventeen eligible studies were identified. Subjects with primary hyperparathyroidism were 3.34 kg (95% confidence interval, 1.97-4.71; P < 0.00001) heavier than controls in 13 studies reporting body weight. In four studies reporting body mass index, subjects with primary hyperparathyroidism had an increased body mass index of 1.13 kg/m(2) (-0.29 to 2.55; P = 0.12) compared with controls. Standard mean difference analysis showed that subjects with primary hyperparathyroidism had an increased weight or body mass index of 0.3 sd (0.19-0.40; P < 0.00001) compared with controls. We conclude that patients with primary hyperparathyroidism are heavier than their eucalcemic peers, and that increased body weight may contribute to the reported associations between primary hyperparathyroidism and some extraskeletal complications.