Senin, 25 Maret 2013

The parathyroid hormone

The parathyroid hormone, called parathormone, regulates the calcium-phosphate balance between the blood and other tissues.

Production of this hormone is directly controlled by the calcium concentration of the extracellular fluid bathing the cells of these glands.

Parathormone exerts at least the following five effects:
(1)it increases gastrointestinal absorption of calcium by stimulating the active transport system and moves calcium from the gut lumen into the blood;
(2) it increases the movement of calcium and phosphate from bone into extracellular fluid. This is accomplished by stimulating osteoclasts to break down bone structure, thus liberating calcium phosphate into the blood. In this way, the store of calcium contained in bone is tapped;
(3)it increases re-absorption of calcium by the renal tubules, thereby decreasing urinary calcium excretion;
(4)it reduces the re-absorption of phosphate by the renal tubules
(5)it stimulates the synthesisof 1,25-dihydrixycholecalciferol by the kidney.
If parathyroid glands are removed accidentally during surgery on the thyroid, there would be arise in the phosphate concentration in the blood.

There would also be a drop in the calcium concentration as more calcium is excreted by the kidneys and intestines, and more incorporated into the bone.

This can produce serious disturbances, particularly in the muscles and nerves, which use calcium ions for normal functioning.

Over activity of the parathyroid glands, which can result from a tumor on the glands, produces a weakening of the bones.

This is a condition that makes them much more vulnerable to fracturing because of excessive withdrawal of calcium from the bones.

Sumber : Bpk. Dr. Iskandar Zulkarnain

#posting tugas cyberprenership
    ahmad baihaqi
    NIM 1112503964


Tidak ada komentar:

Posting Komentar