Restoration of reversed whole PTH/intact PTH ratio and reduction in parathyroid gland vascularity during cinacalcet therapy for severe hyperparathyroidism in a uraemic patient.

Parathyroid hormone (PTH) levels measured with the intact PTH assays are generally higher than those measured with the whole PTH assay; however, rare exceptions to this rule have been reported in patients with severe hyperparathyroidism associated with N-PTH overproduction. We report a haemodialysis patient with severe secondary hyperparathyroidism, in whom abnormally higher whole PTH levels than intact PTH levels were normalized during cinacalcet therapy. Moreover, we observed a marked reduction in parathyroid gland vascularity during this treatment. Our findings suggested that increased sensitivity of the parathyroid calcium sensing receptor by calcimimetics may modulate the secretion or truncation of N-PTH or other PTH molecules that can be detected by the whole PTH assay but not by the intact PTH assays.