Which hormone is known as the "phosphate trashing hormone"?

The hormone referred to as the "phosphate wasting hormone" is indeed parathyroid hormone (PTH). PTH is primarily secreted by the parathyroid glands and plays a crucial role in calcium and phosphate metabolism. When released, PTH promotes the reabsorption of calcium from the urine back into the bloodstream while simultaneously promoting the excretion of phosphate by the kidneys. This action effectively lowers phosphate levels in the blood, earning it the nickname "phosphate trashing hormone."

The physiological importance of PTH lies in its ability to maintain calcium homeostasis and influence bone health. By reducing phosphate reabsorption, PTH helps prevent elevated phosphate levels that can lead to calcification in soft tissues and bone disorders. It also indirectly stimulates the conversion of vitamin D into its active form, which enhances intestinal absorption of calcium and phosphate.

The other options do not have the same function regarding phosphate regulation. Calcitonin primarily lowers blood calcium levels and does not significantly affect phosphate excretion. Vitamin D, while important in calcium and phosphate metabolism, facilitates their absorption in the gut rather than promoting phosphate waste. Cortisol is a glucocorticoid that impacts various metabolic pathways but does not specifically regulate phosphate levels like PTH does.