**Core Concept**
Parathormone (PTH), also known as parathyroid hormone, is a hormone secreted by the parathyroid glands that plays a crucial role in regulating calcium levels in the blood. It acts to increase calcium absorption from the gut by stimulating the release of calcium from bones and increasing renal calcium reabsorption.

**Why the Correct Answer is Right**
PTH acts on the distal convoluted tubules and collecting ducts of the kidneys to increase calcium reabsorption. It also stimulates the release of calcium from bones by acting on osteoclasts. Furthermore, PTH increases the synthesis of 1,25-dihydroxyvitamin D (calcitriol), the active form of vitamin D, which enhances calcium absorption from the gut. This process involves the activation of vitamin D receptors (VDRs) in the intestinal epithelial cells, leading to increased expression of calcium transport proteins.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because PTH does not act on the pancreas to increase calcium absorption. The pancreas is involved in regulating blood glucose levels through the release of insulin and glucagon.
**Option B:** This option is incorrect because PTH does not act on the adrenal glands to increase calcium absorption. The adrenal glands are involved in regulating electrolyte balance and stress response through the release of aldosterone and cortisol, respectively.
**Option C:** This option is incorrect because PTH does not act on the liver to increase calcium absorption. The liver is involved in regulating glucose and lipid metabolism through the release of bile and various hormones.

**Clinical Pearl / High-Yield Fact**
PTH also has a role in regulating phosphate levels in the blood by increasing phosphate excretion in the urine. This is achieved through the activation of the sodium-phosphate cotransporter in the proximal convoluted tubules of the kidneys.

**Correct Answer: C. The distal convoluted tubules and collecting ducts of the kidneys.**