Answer:
Parathyroid hormone (PTH) is a hormone produced by the parathyroid glands, which are four small glands located behind the thyroid gland in the neck. PTH plays a crucial role in regulating calcium and phosphate levels in the body. It primarily affects renal (kidney) processes in the following ways:
Calcium Reabsorption: One of the main actions of PTH on the kidneys is to increase the reabsorption of calcium from the urine. PTH acts on the renal tubules, specifically on the distal convoluted tubules, to enhance the reabsorption of calcium. This helps to conserve calcium in the body, preventing excessive loss through urine.
Phosphate Excretion: PTH has an opposing effect on phosphate compared to calcium. While it promotes the reabsorption of calcium, it inhibits the reabsorption of phosphate in the renal tubules. This leads to increased excretion of phosphate in the urine. The net result is the maintenance of an appropriate balance between calcium and phosphate levels in the bloodstream.
Activation of Vitamin D: PTH stimulates the activation of vitamin D in the kidneys. The inactive form of vitamin D (calcidiol) is converted into its active form (calcitriol) in the kidneys under the influence of PTH. Active vitamin D plays a crucial role in the absorption of calcium and phosphate from the gastrointestinal tract, contributing to the overall regulation of calcium and phosphate homeostasis.
The actions of PTH on the kidneys are part of a complex feedback system that helps maintain the balance of calcium and phosphate in the bloodstream. When blood calcium levels drop, the parathyroid glands release PTH to increase calcium levels by acting on the kidneys, bones, and intestines. This feedback loop is essential for normal bone health, nerve function, and other physiological processes that depend on appropriate calcium and phosphate concentrations in the body.
Step-by-step explanation: