Effects of Long-Term Cinacalcet Administration on Parathyroid Gland in Hemodialysis Patients with Secondary Hyperparathyroidism

Abstract

Background/Aim: Cinacalcet, an allosteric modulator of the calcium (Ca) sensing receptor, reduces the level of parathyroid hormone (PTH) in serum as well as parathyroid gland volume following administration in hemodialysis patients with secondary hyperparathyroidism, though long-term results are yet to be reported. Methods: Serum parameters (n = 23), together with total parathyroid gland volume (n = 18), were determined in Japanese hemodialysis patients given cinacalcet treatment for 8 years. Results: Following initiation of cinacalcet therapy, levels of serum Ca, phosphate, and intact PTH were significantly decreased. Furthermore, the baseline total volume of the parathyroid gland was 1,272 mm3 (496–2,836 mm3), which was then decreased after 6 months to 796 mm3 (377–1,146 mm3) and then to 332 mm3 (175–570 mm3) after 8 years. There was significant positive correlation between parathyroid gland volume at the start of cinacalcet treatment and reduction in volume during the 8 years cinacalcet treatment. The dose of phosphate binder was significantly decreased in a time-dependent manner after 8 years of cinacalcet treatment, likely because serum phosphate showed a progressive decrease with the treatment. Conclusion: In the present patients, long-term treatment with cinacalcet progressively decreased the total volume of parathyroid glands, as well as levels of intact PTH and phosphate in serum in a time-dependent manner. On the contrary, cinacalcet administration did not cause secondary failure or over-suppress the transition of parathyroid gland activity to hypoparathyroid status. These results suggest that cinacalcet treatment may postpone the need for parathyroidectomy and/or reduce its use even after long-term administration for up to 8 years.