Page 125 - Clinical Biochemistry

 Tumors in the parathyroids elevate the level of PTH causing a rise in the level of blood
Ca+2 at the expense of calcium stores in the bones.

 Rise of calcium level may be withdrawn from the bones that they become brittle and break.
B. Hypoparathyroidism
 Causes:
• Accidental removal of or damage to the parathyroids during neck surgery.
• Inherited mutations in the PTH gene.
• Inherited predisposition to an autoimmune attack against the parathyroids.
 Treatment:
• Give calcium supplements
• Give calcitriol 1,25[OH]2 vitamin D3
5- The Pancreas
 The islets are endocrine tissue containing four types of cells. In order of abundance, they
are the:
1- Beta cells, which secrete insulin & amylin.
2- Alpha cells, which secrete glucagon.
3- Delta cells, which secrete somatostatin.
4-Gamma cells, which secrete a polypeptide of unknown function.
1-Beta Cells
I-Insulin:
• Is a small protein consisting of an alpha chain of 21 amino acids linked by two disulfide

(S—S) bridges to a beta chain of 30 amino acids.
• Beta cells have channels in their plasma membrane that serve as glucose detectors.
• Beta cells secrete insulin in response to a rising level of circulating glucose ("blood sugar").
Insulin affects many organs.
(A) It stimulates skeletal muscle fibers to:
a- Take up glucose and convert it into glycogen.
b- Take up amino acids from the blood and convert them into protein.
(B) Acts on liver cells to:
a- Stimulating them to take up glucose from the blood and convert it into glycogen.
b- Inhibiting production of the enzymes involved in breaking glycogen back down

("glycogenolysis")
c- Inhibiting "gluconeogenesis"; that is, the conversion of fats and proteins into glucose.
(C) Acts on fat (adipose) cells: to stimulate the uptake of glucose and the synthesis of fat.