Introduction: Nephrolithiasis and osteoporosis are more common in people with primary hyperparathyroidism (PHPT), although the clinical factors associated with this risk are not well characterised. Recent evidence has suggested parathyroid hormone concentration, but not calcium, is associated with mortality in PHPT.
Methods: Retrospective analysis of all patients presenting to the Edinburgh Centre for Endocrinology & Diabetes with PHPT between 2006 and 2014 (n = 611).
Results: Renal stones were present prior to diagnosis in 10% and detected in 3.9% following diagnosis. Only 4.2% of all renal imaging detected asymptomatic stones following the diagnosis of PHPT. Logistic regression identified younger age (P<0.001) and male gender (P=0.01) as independent predictors of nephrolithiasis. Osteoporosis was present in 49%. Logistic regression identified higher age (P<0.0001), higher PTH (P<0.05) and lower creatinine (P=0.001) as independent predictors of osteoporosis. In patients where parathyroidectomy was not performed, higher PTH (P=0.001), older age (P<0.0001) and male gender (P=0.03) were independent predictors of mortality. Vitamin D concentration was available in 69%; when added to the mortality model, vitamin D deficiency (P=0.03), but not PTH, was independently predictive. PTH concentration was not associated with pre-existing cardiovascular disease, body mass index or age.
Conclusion: PTH concentration at diagnosis of PHPT was not associated with the risk of nephrolithiasis and was relatively weakly associated with the risk of osteoporosis. PTH was associated with subsequent mortality but this relationship may be driven by differences in vitamin D sufficiency. Determining, the dominant direction of this relationship is complex as PTH drives hydroxylation of cholecalciferol to active metabolites but vitamin D deficiency also stimulates PTH release. A large randomised trial of surgical intervention in cases not meeting current criteria for surgery is desirable.