**Core Concept**
Calcium homeostasis is tightly regulated by hormones and organs, with parathyroid hormone (PTH) playing a crucial role in maintaining serum calcium levels. PTH acts on various tissues, including the intestine, to promote calcium absorption.

**Why the Correct Answer is Right**
PTH stimulates the release of 1,25-dihydroxyvitamin D (calcitriol) from the kidneys, which in turn increases the absorption of calcium from the intestine. This is achieved through the activation of vitamin D receptors in the intestinal epithelial cells, leading to increased expression of calcium-binding proteins and transporters. As a result, more calcium is absorbed from the diet, which helps to maintain normal serum calcium levels. This is an essential mechanism, especially during periods of calcium deficiency or increased demand.

**Why Each Wrong Option is Incorrect**
**Option A:** Calcium reabsorption primarily occurs in the proximal convoluted tubule (PCT) and to a lesser extent in the loop of Henle. The distal convoluted tubule (DCT) is not a major site for calcium reabsorption.
**Option B:** Approximately 65% of filtered calcium is reabsorbed in the PCT, while the remaining 35% is excreted in the urine. The glomerulus is responsible for filtering calcium, but it does not excrete a significant amount of calcium.
**Option D:** Parathyroid hormone (PTH) and calcitonin are two hormones that regulate calcium homeostasis, but they have opposing effects. PTH increases calcium levels by promoting its release from bones and increasing its absorption from the intestine, whereas calcitonin decreases calcium levels by inhibiting its release from bones and reducing its absorption from the intestine.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that PTH and vitamin D work synergistically to maintain normal serum calcium levels. PTH stimulates the release of calcitriol, which in turn increases calcium absorption from the intestine. This is a critical mechanism for maintaining bone health and preventing conditions like osteoporosis.

**✓ Correct Answer: C. Parathormone (PTH) promotes absorption of Ca++ from intestine**