Cinacalcet exerts its effect by sensitizing which receptor?

• A. Sensitizes calcium-sensing receptor on parathyroid glands.
• B. Activates vitamin D receptor.
• C. Inhibits PTH synthesis at transcriptional level.
• D. Stimulates calcitonin release.

Answer: (D)

Cinacalcet acts as a calcimimetic, binding allosterically to the calcium-sensing receptor on parathyroid chief cells and increasing its sensitivity to extracellular calcium. When this receptor is more responsive, the parathyroid glands decrease PTH secretion (and can reduce PTH synthesis), helping to lower elevated PTH levels seen in secondary hyperparathyroidism. This mechanism is distinct from activating the vitamin D receptor, directly inhibiting PTH transcription, or stimulating calcitonin release. The calcium-sensing receptor on the parathyroids is the actual target mediating cinacalcet’s effect.