CALCIUM HOMEOSTASIS

DR. MD. MAHBUBUR RAHMAN

MBBS, M Phil, MSc (Biotechnology)

ASSISTANT PROFESSOR

DEPT. OF BIOCHEMISTRY

RAJSHAHI MEDICAL COLLEGE

After the end of the session student will able to know the

• Distribution of calcium in our body

• Biomedical importance of calcium

• Calcium Homeostasis

• Role of PTH on calcium level

Biomedical Importance of Calcium

1. Blood Clotting Factor 2.Nerve conduction 3.Muscle contraction 4.Neurotransmitter release 5.Membrane transport 6.Acts as a Cofactor of an enzyme

CALCIUM

Total amount in adult human 1100 gm

99 % in the skeleton

Plasma level 10mg/dl or 2.5mmol/L

5th most abundant inorganic element

Distribution of calcium in plasma

• Diffusible

– Ionized (Ca+)

– Complexed to Bicarbonate or citrate

Non diffusible

Bound to Albumin

Bound to Globulin

Hypocalcemia in Metabolic alkalosis

Hypocalcemia in Metabolic alkalosis

Calcium in Bone

• Exchangeable Calcium

• Stable Calcium

Calcium Homeostasis

Three Hormone are concerned in calcium regulation

• Parathormone

• Calcitriol

• Calcitonin

Parathormone

• Release from the parathyroid gland

Function of Parathormone

• Increases renal tubular reabsorption

• Augments the action of Calcitriol

• Increase osteoclastic activity

Calcitriol

• Derivatives of Cholesterol (7-dehydrocholesterol)

• Another name 1,25 dihydroxycholecalciferol

• Active form of vitamin D

• First hydroxylation in Liver

• Second hydroxylation in Kidney

Function of Calcitriol

• Increase uptake of calcium by the intestine

• Minimizing loss of Calcium by the Kidney

• Stimulating resorption of bone when necessary

Calcitonin

• Release from parafollicular cell of thyroid gland

Function of Calcitonin

• Decrease resorption of calcium from bone

• Increase loss of calcium in the urine