MICROANATOMY

Detailed explanation-1: -Parathyroid hormone decreases phosphate reabsorption at the proximal convoluted tubule. Phosphate ions in the serum form salts with calcium that are insoluble, resulting in decreased plasma calcium. The reduction of phosphate ions, therefore, results in more ionized calcium in the blood.

Detailed explanation-2: -Physiologic Effects of Parathyroid Hormone In conjunction with increasing calcium concentration, the concentration of phosphate ion in blood is reduced.

Detailed explanation-3: -This hormone raises calcium levels by releasing calcium from your bones, increasing the amount of calcium absorbed from your small intestine and decreasing the amount of calcium lost in urine. When blood-calcium levels are too high, the parathyroid glands produce less parathyroid hormone.

Detailed explanation-4: -Parathyroid hormone increases blood calcium levels when they drop too low. Conversely, calcitonin, which is released from the thyroid gland, decreases blood calcium levels when they become too high. These two mechanisms constantly maintain blood calcium concentration at homeostasis.

Detailed explanation-5: -At the kidneys, PTH increases calcium reabsorption and blocks phosphate reabsorption from the tubules. PTH also acts at the kidneys to stimulate the formation of vitamin D.