Normocalcaemic primary hyperparathyroidism: is nephrolithiasis more common than osteoporosis?

Normocalcaemic primary hyperparathyroidism (NPHPT) is often under-recognised in clinical practice. To determine the prevalence and clinical significance of NPHPT in an unselected sample in an acute hospital setting. Patients aged >18 years who had measurement of an elevated serum parathyroid hormone (PTH ≥ 7 pmol/L) during 12 months from 1 January 2017 to 31 December 2017 were retrospectively studied. NPHPT was defined by the presence of elevated serum PTH with normal albumin-corrected serum calcium on two or more occasions after excluding secondary causes. Patients were followed up for 2 years. Relevant data were collected by review of electronic medical records. Of the 2593 patients who had PTH measured during the study period, 1278 had serum PTH ≥ 7 pmol/L. Hypercalcaemic primary hyperparathyroidism (PHPT) was diagnosed in 174 patients. Secondary causes for elevated serum PTH were identified in 993 patients: 815 (chronic kidney disease - estimated glomerular filtration rate < 60 mL/min/1.73 m2 or renal transplant), 98 (vitamin D deficiency - 25(OH)D < 50 nmol/L), 28 (gastric bypass surgery), 38 (medications), 13 (malabsorption or post-thyroidectomy) and 1 (hypercalciuria). Data were incomplete for 80 patients. The prevalence of NPHPT with and without the exclusion of hypercalciuria was 0.19% (5) and 0.39% (10) respectively. The prevalence of nephrolithiasis in NPHPT was higher than PHPT (100% vs 15% among five patients (P < 0.001) and 50% vs 15% among 10 patients (P = 0.014)). The prevalence of osteoporosis was not significantly different between NPHPT and PHPT (20% vs 45% among five patients (P = 0.389) and 30% vs 45% among 10 patients (P = 0.518)). These findings give further credence to the diagnosis of NPHPT as a clinical entity. Nephrolithiasis may be a greater problem than osteoporosis in NPHPT compared with PHPT. This needs prospective evaluation.

Wu KCJ ，Anpalahan M 《-》

Comparisons Between Normocalcemic Primary Hyperparathyroidism and Typical Primary Hyperparathyroidism.

Normocalcemic primary hyperparathyroidism (NPHPT) was first described in 2008. It is defined as consistently elevated serum parathyroid hormone (PTH) levels with normal serum calcium (sCa) concentration, after excluding secondary causes of PTH elevation. However, the exact definition and management strategy for NPHPT remain controversial. We retrospectively investigated the clinicopathological features and short-term outcomes of NPHPT patients. A total of 280 patients who were surgically indicated for primary hyperparathyroidism (PHPT) at the Yonsei Severance Medical Center between 2015 and 2019 were included. Patients were classified according to preoperative PTH, corrected sCa, and ionized calcium (iCa) levels as follows: typical primary hyperparathyroidism (TPHPT, elevated PTH, sCa, and iCa, n = 158) and NPHPT (elevated PTH, normal sCa, n = 122). NPHPT was commonly seen in younger individuals (aged < 50 years, P = 0.025); nephrolithiasis and bone fractures were common. Preoperative PTH level was higher in the TPHPT group (P < 0.001). The NPHPT group had higher numbers of multiple parathyroid lesions (P = 0.004) that were smaller (P = 0.011). NPHPT patients were further divided into two subgroups according to iCa levels: the elevated (n = 95) and normal iCa (n = 27) groups. There was no significant difference between the two subgroups regarding symptoms and multiplicity of lesions. We found that NPHPT may be a heterogeneous disease entity of PHPT with high rates of multi-gland disease, which appears to be biochemically milder but symptomatic. Intraoperative PTH monitoring might help increase the surgery success rate. Moreover, the short-term outcomes of NPHPT after surgery did not differ from that of TPHPT.

Choi HR ，Choi SH ，Hong N ，Rhee Y ，Kim JK ，Lee CR ，Kang SW ，Lee J ，Jeong JJ ，Nam KH ，Chung WY ... -  《-》

High Rate of Occult Urolithiasis in Normocalcemic Primary Hyperparathyroidism.

Normocalcemic primary hyperparathyroidism (NPHPT) is characterized by elevations in serum parathyroid hormone levels in the presence of normal serum calcium concentrations after exclusion of secondary hyperparathyroidism. We have previously demonstrated no differences in the prevalence of clinically active urolithiasis between NPHPT and hypercalcemic asymptomatic PHPT, and that it is significantly higher in postmenopausal osteoporotic women with NPHPT in comparison to women with normal serum PTH and calcium concentrations. Few studies have addressed the occurrence of silent or occult kidney stones in asymptomatic hypercalcemic PHPT, but no data are available for NPHPT. To determine the presence of occult urolithiasis in NPHPT patients using routine abdominal ultrasonography. We studied 35 patients with NPHPT (mean age 63.2 ± 10.7 years, 96% women; serum PTH 116.5 ± 39.2 pg/mL, 25OHD 38.5 ± 6.82 ng/mL, total calcium 9.1 ± 0.56 mg/dL; albumin 4.02 ± 0.37 g/dL; BUN 34.35 ±10.23 mg/dL; p = 3.51 ± 0.60 mg/dL; estimated glomerular filtration rate 88.44 ± 32.45 mL/min/1.73 m2, and 24-h urinary calcium excretion 140.6 ± 94.3 mg/24 h). The criteria for the diagnosis of NPHPT were as follows: serum PTH above the reference range (11-65 pg/mL), normal albumin-corrected serum calcium concentrations, normal 24-h urinary calcium excretion, serum 25OHD above 30 ng/mL, estimated GFR (MDRD) above 60 mL/min/1.73 m2 (with the exclusion of medications such as thiazide diuretics, lithium, bisphosphonates, and denosumab), a history of clinical symptoms of urolithiasis, and a family history of kidney stones. Thirty-five patients were evaluated and 25 of them met the inclusion criteria. Five patients presented nephrolithiasis corresponding to 20% of the study population. There were no statistically significant differences in any of the clinical or laboratory variables studied between patients with or without urolithiasis, although mean serum PTH levels were higher in patients with stones (180.06 ± 126.48 vs. 100.72 ± 25.28 pg/mL, p = 0.1). The size of the stones ranged from 0.6 to 0.9 cm and all of the stones were located in the renal pelvis. We found a high prevalence of occult kidney stones in NPHPT patients, similar to what is observed in clinically manifested urolithiasis, in hypercalcemic PHPT.

Lemos ALP ，Andrade SRL ，Pontes LLH ，Teixeira PMC ，Bandeira E ，Bandeira LC ，Bandeira F ... -  《-》

Normocalcemic Primary Hyperparathyroidism: A Comparison with the Hypercalcemic Form in a Tertiary Referral Population.

Normocalcemic primary hyperparathyroidism (NPHPT) is a formally recognized variant of primary hyperparathyroidism (PHPT), characterized by normal total and ionized serum calcium concentrations and elevated parathyroid hormone (PTH) levels, in the absence of secondary causes for hyperparathyroidism. NPHPT has been studied previously, but data are limited and confounded. We aimed to compare the clinical and biochemical data of normocalcemic and hypercalcemic subjects in a hospital-based population.We retrospectively analysed the medical records of 131 subjects diagnosed with PHPT at the university hospital Brussels (UZ Brussel) between January 1st 2007 and December 31st 2016, including 25 normocalcemic and 106 hypercalcemic subjects.The mean values of age, BMI, sex, serum 25-OH vitamin D levels and urinary phosphate excretion were comparable between both groups. Subjects diagnosed with NPHPT had significantly lower plasma PTH levels, lower urinary calcium excretion and lower serum creatinine levels compared to the hypercalcemic subjects with PHPT. Corresponding eGFR values were higher in the normocalcemic group. Normocalcemic subjects (NPHPT) presented with a high prevalence of nephrolithiasis (36%), fragility fractures (12%) and osteoporosis (25%). Clinical manifestations and BMD measurements revealed no statistically significant differences between both groups.Our data show a relative prevalence of 19% NPHPT in PHPT. NPHPT may present the earliest form of PHPT with an extension in time, but is not an indolent disease state. Normocalcemic subjects should be managed as hypercalcemic subjects with PHPT. Further research regarding the pathophysiology and natural course of NPHPT is required.

Pierreux J ，Bravenboer B 《-》

The impact of obesity on the presentation of primary hyperparathyroidism.

Tran H ，Grange JS ，Adams-Huet B ，Nwariaku FE ，Rabaglia JL ，Woodruff SL ，Holt SA ，Maalouf NM ... -  《-》