Vitamin D Deficiency is also called as Hypovitaminosis D and is very common form of nutritional deficiency and it is closely associated with calcium level in blood as it plays a major role in calcium regulation in body.

Vitamin D also called Cholecalciferol is a Fat Soluble Vitamin produced naturally in skin where a precursor 7-Dehydrocholestrol is converted into Pre- Cholecalciferol through conrotatory pathway when exposed to Ultra Violet B (UV-B) rays present in sunrays having wavelenght between 290nm-315nm causing electrocyclic reaction with optimal synthesis between 295nm-300nm when exposed for several minutes to form an equilibrium.

This Pre-cholecalciferol finally undergoes (1,7) antarafacial sigmatropic rearrangement to finally isomerize into cholecalciferol, which an inactive form of Vitamin D.

Cholecalciferol further undergoes Hydroxylation in Liver whith help of 25-Hydroxylase in Hepatocytes and is converted to 25-Hydroxycholecalciferol(Calcifediol) which is an inactive form.

Calcifediol further undergoes Hydroxylation in kidney with help of 1-α-Hydroxylase to form (1,25)dihydroxycholecalciferol(Calcitriol) which is an active form of Vitamin D. Parathyroid hormone tightly regulates amount of active Vitamin D circulating in blood by controlled activation of 1-α-hydroxylase.

Vitamin D Deficiency is usually caused due to

• Insufficient exposure to Ultra Violet B radiation from Sun. Person with  dark skin colour are more prone to its deficiency as melanin pigment absorbs UVB and doesnt let it penetrate in skin sufficient enough to activation Vitamin D synthesis. also use of sunscreen peeparations doesnt let sufficient penetration of UVB. Also time and period of exposure, altitude, longitude presence of clouds type of clothing worn by person etc determines its amount of absorption and penetration in skin.
• Insufficient dietary in take of Vitamin D.
• Cholecalciferol(Vitamin D) is converted into 25-Hydroxycholecalciferol in liver. In certain liver diseases this step of metabolism is disturbed and vitamin D is not converted into 25-Hydroxycholecalciferol(Calcifediol).
• 25-Hydroxycholecalciferol(Calcifediol) is further converted into active form that is 1,25-Dihydroxycholecalciferol(Calcitriol) in kidney, certain kidney disease hampers this conversion.

Vitamin D deficiency Symptoms

Vitamin D Deficiency shows not only shows symptoms of its deficiency but also symptoms of calcium deficiency in most cases.

• Osteomalacia
• Osteoporosis
• Triggers Osteoarthritis
• Rickets
• Periodontitis
• Paraesthesia
• Myalgia
• Tetany
• Pre-eclampsia
• Light-Headedness
• Depression

Vitamin D Deficiency Diagnosis 

Vitamin D Deficiency is diagnosed by measuring level of 25-hydroxycholecalciferol in blood.

Normal level of Vitamin D in blood should range between 30-100ng/ml below this upto 20ng is considered as insufficiency and level below 20 ng is considered as Vitamin D Deficiency.

Sources of Vitamin D

• Exposure of Skin to Sunlight
• Fish
• Eggs
• Mushrooms
• Fortified Milk and other food products like oats bread Fortified with Vitamin D.
• Suppliments are available in both oral and injectible forms.

Excess intake of Vitamin D causes Nausea, Vomitting, Constipation , Confussion, Weakness, Kidney stones(urolithiasis).

Also read following related articles

CALCIUM DEFICIENCY

OSTEOPOROSIS

RICKETS