Calcium Homeostasis By Dr. Shereen Samir

Normal level of calcium Calcium is the most abundant essential mineral in the human body. Calcium is the most abundant essential mineral in the human body. In the average adult it range from1000gm. In the average adult it range from1000gm. 99% is present in the bone and teeth. 99% is present in the bone and teeth. 1% is present in the extracellular fluid and blood with a smaller amount inside the cells. 1% is present in the extracellular fluid and blood with a smaller amount inside the cells.

Functions and health benefit of calcium Muscle contraction and nerve excitability. Muscle contraction and nerve excitability. Neurotransmitter and hormonal release. Neurotransmitter and hormonal release. Enzyme function. Enzyme function. Blood coagulation. Blood coagulation. maintain healthy bone and strong teeth. maintain healthy bone and strong teeth. Membrane integrity and permeability. Membrane integrity and permeability.

Calcium regulation Calcium regulation involves three tissues: Calcium regulation involves three tissues: Bone,intestine and kidney. Bone,intestine and kidney. Three hormones : Three hormones : Parathyroid hormone, calcitonine, and activated vitamin D. Parathyroid hormone, calcitonine, and activated vitamin D.

Hormones regulating calcium Parathormone: it is hormone secreted from parathyroid gland. Parathormone: it is hormone secreted from parathyroid gland. It increases calcium blood level It increases calcium blood level It acts on bone,kidney and intestine. It acts on bone,kidney and intestine. It increases calcium reabsorption from kidney and excretion of phosphate. It increases calcium reabsorption from kidney and excretion of phosphate. It increases Ca absorption from intestine It increases Ca absorption from intestine It helps mobilization of Ca from bone. It helps mobilization of Ca from bone.

Calcitonin It is hormone secreted form thyroid gland. It is hormone secreted form thyroid gland. It decreases blood calcium level. It decreases blood calcium level. It helps mobilization of calcium from blood to bone. It helps mobilization of calcium from blood to bone. It stimulates osteoblast cells and inhibit osteoclast. It stimulates osteoblast cells and inhibit osteoclast.

Hormonal control of calcium

Vitamin D It is lipid soluble vitamin. It is lipid soluble vitamin. vitamin D2 &vitamin D3 are the most common types. vitamin D2 &vitamin D3 are the most common types. It is found in fish, liver, oil,egg yolk and animal fat. It is found in fish, liver, oil,egg yolk and animal fat. Vitamin D either ingested or formed in skin is transported to liver. Vitamin D either ingested or formed in skin is transported to liver. In the liver: In the liver: It is transformed to inactive form 25hydroxycholeciferol It is transformed to inactive form 25hydroxycholeciferol In the kidney: In the kidney: It is converted1- 25 dihydroxycaciferol.(vitD)

Normal calcium level Normal Serum calcium = mg/dl Hypocalcemia i.e decreased blood calcium level causes tetany. In children a disease called rickets and in adult osteomalecia Hypercalcemia increase calcium level.

Tetany Increased neuromuscular excitability due to decreased calcium below normal level.(9- 11mg%) Increased neuromuscular excitability due to decreased calcium below normal level.(9- 11mg%) It is a state of spastic contraction of skeletal muscles. It is a state of spastic contraction of skeletal muscles.

Types of tetany Latent tetany: Latent tetany: Calcium level 7-9 mg% Calcium level 7-9 mg% The symptoms are absent during rest but appears to emotional stress,pregnancy &lactation. The symptoms are absent during rest but appears to emotional stress,pregnancy &lactation. Manifest tetany: Manifest tetany: Plasma calcium level drop below 7mg%. Plasma calcium level drop below 7mg%.

Regulation of blood glucose

-The normal blood glucose level ranges between mg/100 ml blood. -This level is controlled by the following hormones: 1- Pancreatic h. 2- Adrenaline. 3- Glucocorticoids. 4-Thyroxine. 5-Growth h. Endocrine regulation of blood glucose

Importance of blood glucose regulation: !!! Glucose is the only nutrient that normally can be used by the brain and retina. Glucose is the only nutrient that normally can be used by the brain and retina. Glucose is important source of energy for the cells. Glucose is important source of energy for the cells.

a) Pancreatic hormones -The endocrine cells of the pancreas are present in discrete groups called ‘islets of Langerhan’s’, which are more numerous in the tail than in the body and comprise 1-2% of and comprise 1-2% of its weight.

Four groups of cells are now identified in the islets: 1.Alpha cells,( 25% of islet mass)  glucagon h. 2.Beta cells,(about 60%), located in the centre of the islet.  insulin h. 3.Delta or D cells, (10% of the islet mass)  somatostatin h. 4.F cells, (only about 5%)  pancreatic polypeptide h.

I. Insulin 1-Insulin  blood glucose level by: a. Glycogenesis b. Inhibition of glycogenolysis c.  glucose uptake by the tissues d-  gluconeogenesis 5.  transformation of glucose into fat.

2- Anabolic action 2- Anabolic action Insulin is an essential hormone for growth: a)In muscle, insulin stimulates the uptake of certain amino acids across the cell membrane. b)Insulin also stimulates the rate of protein synthesis. c) Anti-catabolic effects i.e. it inhibits proteolysis. 2.Insulin increases cellular uptake of potassium, phosphate and magnesium. 3.It increases the reabsorption of potassium, phosphate and sodium by renal tubules

Regulation of secretion - The major regulation is the plasma glucose level (no insulin when glucose < 50 mg%). - A half maximum insulin secretion occurs at a plasma glucose level of about 150 mg% and a maximum response at 300 to 500 mg%. - GIP (glucose dependent insulinotropic peptide), gastrin, secretin, Cholecystokinin, pancreatic glucagons - Oral protein, Triglycerides and fatty acids

II. Glucagon -Glucagon is a hyperglycemic polypeptide from α cells. 1.  glucose:  glycogenolysis and  gluconeogenesis 2.  lipolysis and  hepatic cholesterol synthesis. 4.Natriuresis, by  renal tubular Na + reabsorption 5.  myocardial contractility   COP. 6.A local CNS h. for regulation of appetite.

1. Glucagon release is stimulated by: a) Hypoglycaemia  2-4 fold  in glucagon level. b) Protein meal c)  FFA. d) Exercise. e)Vagal stimulation or administration of acetylcholine. f)Stress, including infection, toxaemia, burns and major surgery. g) Growth hormone.

2. Glucagon release is inhibited by a)Hyperglycaemia:  glucagon level by 50%. b)  FFA. c) Somatostatin.

B) Other hormones which regulate blood glucose level 1.Adrenaline: -glycogenolytic on liver and muscles. -glycogenolytic on liver and muscles.2.Glucocorticoids: I-  gluconeogenesis. I-  gluconeogenesis. II-  glucose uptake by the tissues. II-  glucose uptake by the tissues.

3.Growth hormone: -  glucagon hormone. -Inhibits glucose uptake by tissues. 4.Thyroxin: -  glucose absorption from intestine. -  glycogenolysis. The net result is a rise in blood glucose level.

Danger of increased blood glucose: (Diabetes Mellitus) 2 forms of diabetes mellitus: 2 forms of diabetes mellitus: Type I: insulin dependent diabetes (IDDM). Type I: insulin dependent diabetes (IDDM). Type II: non-insulin dependent diabetes (NIDDM). Type II: non-insulin dependent diabetes (NIDDM).

Diabetes Mellitus

Diabetes mellitus It results from deficiency of insulin action, which leads to: 1.Hyperglycaemia: - due to absence of effects of insulin. - due to absence of effects of insulin. 2.Glucosuria: i.e loss of glucose in urine. - when the blood glucose level becomes > - when the blood glucose level becomes > renal threshold (180 mg%). renal threshold (180 mg%).

3.Polyuria due to: a)Excretion of glucose in urine. b)  osmotic pressure of the blood  drags water out of the cells towards the blood. -This causes dehydration of the tissue cells. 4.Polydepsia:intense thirst due to dehydration.

5. Acidosis: - Due to inhibition of carbohydrate metabolism. - Due to inhibition of carbohydrate metabolism. -The body depends on the fat metabolism which supplies most of the energy needed. -The body depends on the fat metabolism which supplies most of the energy needed. -Uncontrolled diabetes  accumulation of acetoacetic acid and beta hydroxybuteric acid  acidosis. -Uncontrolled diabetes  accumulation of acetoacetic acid and beta hydroxybuteric acid  acidosis.

6.Loss of weight and asthenia: -Due to mobilization of fat and proteins for supply of energy. 7.  cholesterol and TG in blood: - early development of arteriosclerosis.