Managing bone and mineral disorders associated with chronic kidney disease (CKD-MBD) in children is a complex task. Controlling parathyroid hormone (PTH) levels involves adjusting calcium intake, managing hyperphosphatemia, intensive dialysis, and considering specific therapies like active vitamin D analogues and cinacalcet.

Cinacalcet, authorized in Europe since 2017 for children over 3 undergoing dialysis with secondary hyperparathyroidism (SHPT), has shown efficacy in reducing PTH levels. The 2019 guidelines call for its use with caution particularly to avoid hypocalcemia, in children with severe hyperparathyroidism despite optimized conventional treatments.

In adults, cinacalcet has been found to reduce serum PTH, calcium, and phosphate levels, decrease the risk of vascular calcification, and have a positive effect on bone formation. This suggests that cinacalcet may slow the progression of cardiovascular calcifications.

Additionally, Professor Shroff has introduced a non-invasive method for assessing bone calcium status by analyzing stable calcium isotope ratios in blood. This method would allow to determine whether a treatment such as cinacalcet has a positive influence on bone calcium balance, a key element in the management of CKD-MBD.

Inclusion Criteria:

• Children from 3 to 17 years of age
• On maintenance dialysis : hemodialysis, hemodiafiltration, peritoneal dialysis
• Patient who begin treatment with cinacalcet based on the 2019 European guidelines and at the discretion of the treating physician
• With normal QTc interval on electrocardiogram
• With total serum calcium >2.40 mmol/L
• With heamoglobin > 8g/dl
• Non - opposition from parents/legal guardians

Exclusion Criteria:

• Children < 12 kg
• Persons deprived of their liberty by a judicial or administrative decision
• Persons under psychiatric care
• Persons admitted to a health or social institution for purposes other than research
• Persons not affiliated to a social security scheme or beneficiaries of a similar scheme
• Persons participating in other interventional research with an exclusion period still in progress at pre-inclusion
• Patients who received cinacalcet with 3 months prior inclusion

This study will involve children above 3 years of age on maintenance dialysis (hemodialysis, hemodiafiltration, peritoneal dialysis) who begin treatment with cinacalcet.