This is a single arm, open-labelled study to determine the effectiveness of combination Cinacalcet with Vitamin D analogue in the treatment of severe hyperparathyroidism in patients with ESRF on haemodialysis. Patients will be started on PO Cinacalcet 25mg OD + PO/IV active Vitamin D analogues adjusted by increments/decrements in steps of 1 mcg 3x per week every 1-4 weeks until the corrected calcium level is within 2.4-2.54 mmol/L. After iPTH has reached 2-9x ULN, patient enters maintenance phase. If serum calcium falls below 2.1mmol/L, active Vit D dose will be increased and if it is above 2.54 mmol/L, the dose will be decreased.

Percentage reduction of iPTH levels from baseline at 6,12 and 24 months treatment and Percentage of patients achieving iPTH levels within the target range of 2-9x upper limit normal at 6, 12 and 24 months will be determined

Many patients on haemodialysis will develop secondary hyperparathyroidism. Vitamin D analogues such as alphacalcidol are needed to bring their iPTH levels down to normal. However, these analogues can cause hypercalcaemia, thus its doses are limited by this effect. Cinacalcet, which is currently not widely available to patients in hospitals, is a calcimimetic that can reduce both iPTH and serum calcium levels. No studies have yet to be carried out investigating the outcome of using low doses of Cinacalcet as a means of optimizing doses of vitamin D analogues by keeping calcium levels from going over the upper limit. So a single arm, open-labelled study has been designed to determine the effectiveness of combination Cinacalcet with Vitamin D analogue in the treatment of severe hyperparathyroidism in patients with ESRF on haemodialysis. No formal sample size calculation was done as this is a proof of concept study. Power calculation will be done at the end based on the primary outcome of the study.

Methodology: Patients will be started on PO Cinacalcet 25mg OD + PO/IV active Vitamin D analogues adjusted by increments/decrements in steps of 1 mcg 3x per week every 1-4 weeks until the corrected calcium level is within 2.4-2.54 mmol/L. After iPTH has reached 2-9x ULN, patient enters maintenance phase. If serum calcium falls below 2.1mmol/L, active Vit D dose will be increased and if it is above 2.54 mmol/L, the dose will be decreased.

Percentage reduction of iPTH levels from baseline at 6,12 and 24 months treatment and Percentage of patients achieving iPTH levels within the target range of 2-9x upper limit normal at 6, 12 and 24 months will be determined.

Inclusion Criteria:1. End Stage Renal Failure (ESRF) patients on haemodialysis with iPTH levels more than 9x upper limit normal 2. Patients who has history of active Vitamin D analogue doses limited by hypercalcaemia (>2.54 mmol/L)

Exclusion Criteria:

1. Pregnant or breastfeeding or planning to become pregnant
2. Life expectancy of 6 months or less
3. History of decompensated liver disease