**Core Concept**
Cinacalcet is a calcimimetic agent that modulates the activity of the calcium-sensing receptor (CaSR) in the parathyroid gland, leading to a decrease in parathyroid hormone (PTH) secretion.

**Why the Correct Answer is Right**
Cinacalcet acts by binding to the CaSR on the surface of parathyroid cells, which increases the sensitivity of the receptor to extracellular calcium ions. This results in a decrease in PTH secretion, as the parathyroid gland senses higher levels of calcium and reduces hormone production. The decrease in PTH levels leads to a decrease in serum calcium levels, which is beneficial in patients with secondary hyperparathyroidism.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because cinacalcet does not act by inhibiting the secretion of PTH. While it does decrease PTH levels, it does so by modulating the CaSR, not by directly inhibiting hormone secretion.

**Option B:** This option is incorrect because cinacalcet does not act by increasing the excretion of calcium in the urine. Its mechanism is centered on the modulation of the CaSR, not on altering calcium excretion.

**Option C:** This option is incorrect because cinacalcet does not act by inhibiting the reabsorption of calcium in the kidneys. While it does decrease serum calcium levels, its mechanism is centered on the modulation of the CaSR, not on altering calcium reabsorption.

**Clinical Pearl / High-Yield Fact**
Cinacalcet is often used in the treatment of secondary hyperparathyroidism in patients with chronic kidney disease, where it helps to control serum calcium levels and reduce the risk of bone disease.

**Correct Answer:** C. Cinacalcet acts by binding to the calcium-sensing receptor (CaSR) on the surface of parathyroid cells, increasing the sensitivity of the receptor to extracellular calcium ions and leading to a decrease in parathyroid hormone (PTH) secretion.