Elderly patients with chronic kidney disease have higher risk of hyperparathyroidism.

PURPOSE: As the world's population ages, the incidence of chronic kidney disease (CKD) is growing. There is ongoing debate regarding whether high levels of parathyroid hormone (PTH) would be more common in elderly than young patients, and which factors are driven the risk of secondary hyperparathyroidism (SHPT), independent of renal function.

METHODS: Elderly patients (age ≥ 65 years, N = 518) were compared to a 1:1 sex- and estimated glomerular filtration rate (eGFR)-matched sample of young patients (age < 65 years), in a cross-sectional analysis. Demographic, biochemical and drug prescription data were collected from electronic charts. The main outcome measure was the prevalence of SHPT, defined as PTH > 65 pg/mL.

RESULTS: Elderly patients presented higher serum calcium and PTH levels and lower serum phosphate, and were taking more diuretics than young patients. SHPT was more frequent among elderly patients (49.4 vs. 38.6%, p = 0.005), and it was associated with lower eGFR, low levels of 25(OH) vitamin D and with furosemide therapy, while thiazide use was a protector factor. Elderly patients with 25(OH) vitamin D > 40 ng/mL were protected against SHPT. The Ca/PTH ratio was lower in elderly than in young patients [0.15 (0.10, 0.20) vs. 0.16 (0.11, 0.23), respectively, p = 0.003].

CONCLUSION: CKD elderly patients have higher risk of SHPT than young, which cannot be explained solely by renal function. Besides low levels of vitamin D, furosemide therapy and a distinct relationship between calcium and PTH are possible factors contributing to SHPT. Whether this is a result of renal resistance to PTH or an altered set point to calcium deserves further investigation.