The secretion of PTH is regulated by

The secretion of parathyroid hormone (PTH) is indeed regulated by the levels of calcium ions in the blood.

Parathyroid hormone (PTH) is produced by the parathyroid glands, which are small glands located in the neck near the thyroid gland. PTH plays a crucial role in regulating calcium and phosphorus levels in the bloodstream. When blood calcium levels decrease, the parathyroid glands release more PTH. Conversely, when blood calcium levels are elevated, the secretion of PTH is reduced.

The main actions of PTH include:

• PTH promotes the release of calcium from bones into the bloodstream. This helps maintain the appropriate levels of calcium in the blood.
• PTH increases the reabsorption of calcium by the kidneys, reducing its excretion in the urine. This helps to conserve calcium within the body.
• PTH stimulates the production of calcitriol, the active form of vitamin D. Calcitriol enhances calcium absorption from the intestines, further aiding in maintaining blood calcium levels.