Elevated parathyroid hormone 44-68 in idiopathic calcium pyrophosphate dihydrate crystal deposition disease. Role of menopause and iron metabolism?

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.