MON-LB091 An Overview of the Etiology, Clinical Manifestations, Management Strategies, and Complications of Hypoparathyroidism from the Canadian National Hypoparathyroidism Registry

The Canadian National Hypoparathyroidism Registry (CNHR) was formed in 2014 and enrolment of prevalent and incident cases began following approval by McMaster University Ethics Review Board. Objective(s): • identify the etiology and presenting symptoms of patients with hypoPTH. • assess differences in presentation based on etiology of the disease. • compare parameters of calcium homeostasis amongst those developing complications of nephrolithiasis or nephrocalcinosis and those without complications. • assess fracture risk in Canadian patients with hypoPTH. Material and Methods: 118 patients aged >18 years registered in the CNHR were reviewed as per the following inclusion criteria: 1. Chronic HypoPTH (low PTH in the presence of low serum calcium total or ionized below normal reference range for at least 6 months prior to enrolment) 2. HypoPTH (including post-surgery) requiring calcium/calcitriol replacement to maintain normal calcium (total or ionized calcium level for at least 6 months prior to enrolment 3. Pseudohypoparathyroidism with elevated PTH and low serum calcium (total or ionized) normal vitamin D and hyperphosphatemia were included. We reviewed etiology, clinical presentation, biochemical profile, management strategies, markers of skeletal health including fractures, bone mineral density (BMD), fracture risk and complications including nephrolithiasis/nephrocalcinosis, and basal ganglia calcification. Results: Most patients (72%) had postsurgical hypoparathyroidism, followed by idiopathic/autoimmune disease (25%) and pseudohypoparathyroidism (3%). The mean age of onset was 42.0 years, with mean duration of follow-up of 4 years. All patients were taking calcium supplements (100%); calcitriol was taken by 82.2% and 6 patients were receiving parathyroid hormone. Nephrolithiasis or nephrocalcinosis were present in 24.6% of treated patients despite a mean calcium phosphate product <4.4 mmol2/L2. Basal ganglia calcification was present in 8 of the 30 patients reviewed. Hospitalization was required in 40 of the 118 patients for symptoms of hypocalcemia. Conclusion: 1. HypoPTH is associated with a significant disease burden and leads to hospitalization in a large number of patients. 2. Renal complications were present in 24.6% of treated patients despite maintenance of a calcium phosphate product in the desired range (<4.4 mmol2/L2). The ideal calcium phosphate product needs to be reconsidered. 3. Fracture risk was low in the absence of traditional osteoporosis risk factors. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.