Objective: To examine whether idiopathic calcium pyrophosphate dihydrate (CPPD) crystal deposition disease (CDD) is related to altered parathyroid hormone (PTH) metabolism.
Methods: Forty-two patients with idiopathic CPPD CDD were compared with 67 controls, 33 of whom were matched for age and sex.
Results: Serum PTH 44-68 concentrations were elevated in 29% of patients and were significantly higher in the patients than in their sex- and age-matched controls (Z = -4.664, p < 0.0001). PTH 1-84 levels were normal. Serum calcium, phosphorus, and ferritin levels were normal, but were significantly higher in the patients. Serum PTH 44-68 levels correlated negatively with serum transferrin in female controls aged >or= 45 years, and with transferrin saturation in the female patients. Correlation between serum ferritin and age was linear and positive in the former subjects and quadratic in the latter.
Conclusion: Elevated serum concentration of PTH mid-fragments containing the 44-68 region could explain the joint disorders associated with idiopathic CPPD CDD, as shown in genetic hemochromatosis. In female patients the elevation of PTH mid-fragments could be linked to changes in iron metabolism provoked by the menopause.