Question

Describe the relationship between parathyroid hormone (PTH) and blood calcium. Include the three (3) systems PTH targets to alter blood calcium and explain the effects of inappropriate PTH secretion (too much PTH and too little PTH).

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Answer 1

Calcitonin decrease the blood calcium level by stimulating the osteoblastic activity of the bone and inhibiting the osteoclast.
Parathyroid harmones has action opposite to Calcitonin. It increases the blood calcium by:

1) It increases the bone resorption by stimulating the Osteoclastic activity thereby decreasing calcium deposition in the bone and increasing the calcium concentration of the blood.

2)It increases the vitamin D synthesis. Vitamin D increases the absorption of Calcium form Kidney and intestine and therefore increase the blood calcium level.

3) It increases the absorption of calcium from kidney.

Hyperparathyroidism, a disease wherein there is excessive parathyroid hormone production by the parathyroid gland (a small gland located near the thyroid gland). Normally, the parathyroid hormone maintains blood calcium levels by, in part, removing calcium from the bone. In untreated hyperparathyroidism, excessive parathyroid hormone causes too much calcium to be removed from the bone, which can lead to osteoporosis.

Low level of parathyroid hormone is called hypoparathyroidism that leads to low level of calcium.