Vitamin D Deficiency

Describe sources, recommended daily allowance, biological functions, and deficiency manifestations of vitamin D
Answer.

Vitamin D

The active form of Vitamin D is calcitriol (1, 25-dihydroxy cholecalciferol)

Daily Requirement

The daily requirement of calcitriol is 200 to 400 IU

1 IU = 0.025 micrograms of cholecalciferol

Dietary Sources

Functions Of Vitamin D.

Calcitriol increases the intestinal absorption of calcium and phosphorus by increasing the synthesis of calcium-binding protein. This protein increases calcium absorption by the intestine.
In the osteoblasts of the bone, calcitriol stimulates calcium uptake for deposition as calcium phosphate. Thus, calcitriol is essential for bone formation.
Calcitriol increases the reabsorption of calcium and phosphorus by the kidney and thus decreases their excretion in the urine.

Deficiency Of Vitamin D

There are 3 types of vitamin D deficiency:

Rickets

Vitamin D deficiency in children is known as rickets.
In the absence of vitamin D, the osteoblast proliferation is not accompanied by vascularization and mineralization at the normal rate.
The bones become soft.
Bending of long bones gives rise to deformities such as bow legs and knock knees.
The ankles, knees, wrists, and elbows are swollen.
The fontanelles do not close properly, giving rise to a hot cross bun appearance of the head.
The ribs give a beaded appearance, known as a ricket rosary.
The chest gives a pigeon breast appearance.
Teeth erupt late and are deformed

Osteomalacia

Vitamin D deficiency in adults is known as osteomalacia
Osteomalacia is seen in pregnancy and lactation, when there is an additional requirement of vitamin D and its drainage in the milk
Osteomalacia is also seen in women who observe purdah and in areas where sunshine is scanty
In osteomalacia, the bones become soft and are easily fractured
It particularly affects the pelvic bones

Renal Osteodystrophy

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