Biochemical changes over 12 months following cessation of cinacalcet included an increase in serum parathyroid hormone (PTH) (42.2 [IQR 27.8–94.6] pmol/L to 114.8 [83.9–159.1] pmol/L [p < 0.001]), serum calcium (2.31 ± 0.21 mmol/L to 2.46 ± 0.14 mmol/L [p < 0.001]) and primary CPP (CPP-I) (p = 0.002). The gene discussed is PTH; the disease is central precocious puberty.