Is Normocalcemic Primary Hyperparathyroidism Harmful or Harmless?

Context: Primary hyperparathyroidism (PHPT) is reported to be associated with an increased frequency of hypertension, however, information in this regard is sparse in relation to normocalcemic primary hyperparathyroidism (NPHPT). Objective: The aim of this study was to determine the association between NPHPT and blood pressure. Design, Setting, and Patients: We retrospectively enrolled 940 patients who visited the Fujian Provincial Hospital between September 2010 and December 2013 with a measured serum parathyroid hormone (PTH) and calcium level. Among them, 11 patients were diagnosed with NPHPT, while 296 cases with normal PTH and albumin-adjusted serum calcium. Main Outcomes Measures: Systolic blood pressure (SBP), diastolic blood pressure (DBP), intact serum PTH, and serum calcium were recorded. Results: There were no significant differences between subjects identified with NPHPT and those with normal PTH in terms of age, sex, body mass index, serum calcium, 25-Hydroxyvitamin D, serum creatinine, fasting plasma glucose, triglycerides, total cholesterol, high density lipoprotein, and low density lipoprotein. The subjects with a diagnosis of NPHPT had higher levels of SBP (141.9 ± 20.2 vs 131.2 ± 16.5, P = .041) and DBP (85.2 ± 12.4 vs 76.8 ± 10.3, P = .026) than the subjects in the cohort with normal PTH. After adjustment for all potential confounders, risks (odds ratios and 95% confidence interval) of SBP and DBP in NPHPT patients were 1.035 (1.000, 1.071) and 1.063 (1.004, 1.125), respectively (P < .05). Conclusions: The NPHPT had higher risk of high blood pressure than subjects with normal PTH. It is worth considering the necessity of more aggressive therapeutic intervention aimed to normalize PTH even if patients with NPHPT continue to be normocalcemic.