Number of enlarged parathyroid glands might be a predictor of cinacalcet response in advanced secondary hyperparathyroidism.

BACKGROUND: Cinacalcet has been shown to be effective in lowering serum intact parathyroid hormone (iPTH) levels in patients with advanced secondary hyperparathyroidism (SHPT). We investigated clinical factors influencing therapeutic response to cinacalcet for SHPT refractory to active vitamin D sterols. METHODS: A total of 57 hemodialysis patients with SHPT (iPTH >300 pg/mL) were enrolled in this 28-week, prospective, observational study. Cinacalcet was started at an initial dose of 25 mg/day; the dose of cinacalcet was titrated to achieve the following: 3.5 ≤ phosphate (P) ≤ 6.0 mg/dL; 8.4 ≤ adjusted calcium (Ca) ≤ 10.0 mg/dL; 60 ≤ iPTH ≤ 180 pg/mL). Parathyroid ultrasonographic examination was performed at the start of cinacalcet treatment. Patients were divided into two groups on the basis of iPTH levels after 28 weeks: Group A, iPTH ≤180 pg/mL; Group B, iPTH >180 pg/mL. RESULTS: Serum iPTH and P levels at baseline were significantly higher in Group B than Group A. The number of enlarged parathyroid glands (PTGs) (estimated volume ≥500 mm(3) or major axis ≥10 mm), which presumably had nodular hyperplastic lesions, and the largest and the total volume of detectable PTGs were significantly greater in Group B compared with Group A. In our multivariate logistic regression analysis, patients with two or more enlarged PTGs had a significant risk of poor response to cinacalcet treatment (odds ratio 5.68, 95% confidence interval 1.19-32.66, P = 0.0363). CONCLUSION: These results indicate that the number of enlarged PTGs could predict therapeutic response of cinacalcet in patients with advanced SHPT.