Response of secondary hyperparathyroidism to cinacalcet depends on parathyroid size

Several reports have indicated that the measurement of parathyroid gland size assists the management of patients with secondary hyperparathyroidism. This study examined whether parathyroid gland enlargement influenced the response of secondary hyperparathyroidism to cinacalcet.

Clinically stable hemodialysis patients with secondary hyperparathyroidism that was resistant to conventional treatment received cinacalcet for 6 months. Based on the parathyroid gland size measured by ultrasonography, the patients were divided into group S (gland <500 mm(3)) and group L (gland >or=500 mm(3)). Serum levels of intact parathyroid hormone (intact PTH), bone-specific alkaline phosphatase, osteocalcin, and cross-linked N-terminal telopeptide of type 1 collagen were measured over time.

Twenty-four patients completed the study. In group S, all markers of bone metabolism and intact PTH were significantly decreased after 3 months of cinacalcet treatment. In contrast, there were no significant changes of these parameters, except for intact PTH, after 3 months in group L. After 6 months of cinacalcet treatment, however, all of the markers of bone metabolism were significantly decreased in both groups.

The response to cinacalcet differed between groups S and L. Thus, the presence of parathyroid enlargement (nodular hyperplasia) may delay the response of secondary hyperparathyroidism to cinacalcet.