Endocrine Abstracts

Introduction: Normocalcemic Primary Hyperparathyroidism is today considered a variant of Primary Hyperparathyroidism. It is characterized by persistently normal calcium levels and increased levels of parathyroid hormone, after the exclusion of other causes of secondary hyperparathyroidism. We aimed to compare clinical, biochemical and imaging data from patients with normocalcemic and hypercalcemic primary hyperparathyroidism.

Methods: This is a retrospective study from the archives of our Department that included 161 patients (38 men and 123 women), who were monitored from 2010 to 2021, 68 with Normocalcemic Primary Hyperparathyroidism (NPHPT) and 93 with Hypercalcemic Primary Hyperparathyroidism (HPHT). The biochemical tests included calcium, total and adjusted for albumin, phosphorus, magnesium, parathyroid hormone and 25OHD3 levels and 24-h urinary calcium. The imaging tests included thyroid ultrasound, scintigraphy with Tc99 m Sestamibi, kidney ultrasound and bone density measurement. We also, accessed the eligibility for surgical treatment of the disease, according to the criteria of the Fourth International Workshop for the Management of Asymptomatic Primary Hyperparathyroidism.

Results: No differences between the two groups were found regarding, age of diagnosis, body mass index (BMI), serum magnesium and 25OHD3 levels and 24-h urine calcium concentration (P>0.05). Patients with HPHPT had significantly higher levels of corrected calcium (11.3±0.57 vs 9.8±0.44 mg/dl, P<0.001) and PTH (219.2±209.8 vs 111.8±35.5 pg/ml, P<0.001) and lower phosphorus levels (2.7±0.54 vs 2.9±0.43 mg/dl, P<0.01) compared to patients with NPHPT. No differences were found in the prevalence of osteopenia/osteoporosis, fragility fractures and the need to receive anti-osteoporotic treatment (P>0.05). Patients with HPHPT had significantly higher prevalence of nephrolithiasis clinically (history of renal colic: 40.3% vs 25.8%, P<0.05) and discovered by imaging (renal ultrasound: 54.3% vs 34.7%, P<0.03). Patients with HPHPT more often met the criteria for surgical treatment (54.3% vs 34.7%, P<0.001).

Conclusions: Patients with NPHPT often have disease complications, especially osteoporosis, fragility fractures and nephrolithiasis both clinically and through imaging. Until more data on the pathophysiology and natural course of NPHPT are provided, patients with this form of primary hyperparathyroidism should be managed as patients with HPHPT.