Secondary hyperparathyroidism and adverse health outcomes in adults with chronic kidney disease

Background. Secondary hyperparathyroidism (SHPT) develops frequently in patients with chronic kidney disease (CKD). However, the burden and long-term impact of SHPT on the risk of adverse health outcomes are not well studied. Methods. We evaluated all adults receiving nephrologist care in Stockholm during 2006-11 who were not undergoing kidney replacement therapy and had not developed SHPT. Incident SHPT was identified by using clinical diagnoses, initiated medications or two consecutive parathyroid hormone (PTH) measurements >= 130 pg/mL. We characterized SHPT incidence by estimated glomerular filtration rate (eGFR) strata, evaluated clinical predictors and quantified the association between incident SHPT (time-varying exposure) and the risk of fractures, CKD progression, major adverse cardiovascular events (MACEs) and death. Results. We identified 2556 adults with CKD Stages 1-5 (mean age 66 years, 38% women), of whom 784 developed SHPT during follow-up. The incidence of SHPT increased with advancing CKD: from 57 cases/1000 person-years in CKD Stage G3 to 230 cases/1000 person-years in Stage G5. In multivariable analyses, low eGFR was the strongest SHPT predictor, followed by young age, male sex and diabetes. Incident SHPT was associated with a 1.3-fold (95% confidence interval 1.1-1.8) increased risk of death, a 2.2-fold (1.42-3.28) higher risk of MACEs, a 5.0-fold (3.5-7.2) higher risk of CKD progression and a 1.3-fold (1.5-2.2) higher risk of fractures. Results were consistent in stratified analyses and after excluding early events. Conclusions. Our findings illustrate the burden of SHPT in advanced CKD and highlight the susceptibility for adverse outcomes of patients developing SHPT. This may inform clinical decisions regarding pre-SHPT risk stratification, PTH monitoring and risk-prevention strategies post-SHPT development.