Association of Serum Parathyroid Hormone Levels with All-Cause and Cause-Specific Mortality Among U.S. Adults, with a Focus on the Parathyroid Hormone Levels Within the Normal Range: a Population-Based Cohort Study from NHANES 2003-2006.

This study investigated the correlation between serum parathyroid hormone (PTH) levels and the risks of all-cause and cause-specific mortality, with specific focus on the association between serum PTH levels within the normal range and mortality risk. This prospective cohort study included 6633 non-hypoparathyroid participants (aged ≥ 20 years) from the National Health and Nutrition Examination Survey 2003-2006. We employed restricted cubic splines to depict the dose-response relationship between serum PTH and the risks of mortality. Multivariate Cox proportional hazards models were used to calculate the hazard ratios (HR) and 95% confidence intervals (95%CI). Among the 6633 participants, 1309 died during follow-up, including 437 cardiovascular deaths, 316 cancer-related deaths, and 556 non-cardiovascular-non-cancer deaths. Restricted cubic splines suggested that ideal outcomes were observed with serum PTH at the lower level of the normal range (18-41 pg/ml). Compared with participants in the low-normal PTH range (18-41 pg/ml), those in the high-normal range (42-74 pg/ml, accounting for 40.4% of the entire normal range) had 22% (HR:1.22,95%CI 1.02-1.46) and 66% (HR:1.66,95%CI 1.20-2.30) increased risks of all-cause and cardiovascular mortality. Similarly, participants in the high PTH range (> 74 pg/ml) had 34% (HR:1.34,95%CI 1.08-1.68), 59% (HR:1.59,95%CI 1.03-2.46) and 44% (HR:1.44,95%CI 1.02-2.04) increased risks of all-cause, cardiovascular and non-cardiovascular-non-cancer mortality. Among U.S. adults, high-normal and high PTH levels were both associated with higher risks of all-cause and cardiovascular mortality. Further studies are needed to evaluate the clinical implications of screening and management for this high-risk population, especially those with high-normal PTH levels, who account for a substantial proportion of the normal-range population but are usually receiving insufficient clinical attention.