Resource Person:-Prof.Dr.A.K.DuttaPresented by:- Prateek Singh

Vitamin D is a group of fat-soluble prohormones. Two major forms of which are vitamin D2

(or ergocalciferol) and vitamin D3 (or

cholecalciferol).

Produced in skin exposed to sunlight, specifically ultraviolet B radiation.

Production is greatest in the stratum basale and stratum spinosum .

Functions of Vitamin DRegulates the calcium and phosphorus

levels in the blood by promoting their absorption from food in the intestines.

Promotes bone formation and mineralization .

Inhibits parathyroid hormone secretion from the parathyroid gland.

Affects the immune system by promoting immunosuppression, phagocytosis, and anti-tumor activity

Dietary sources of vitamin-D

Fortified foods especially dairy products, cereals and vit. Supplements.

Fish, liver, oils, egg yolk & butter.

Infants: obtain vit D supplement from mothers milk, infant formulas, cow milk .

Why Vitamin D deficiency occurs?

Due to:-

Inadequate sunlight exposure.

Poor access to micronutrients rich food.

Disorder that limit its absorption.

Deficient soil quality.

Impaired conversion into active metabolites.

Possible role of dietary fibers.

These lead to:-Learning disability

Impaired work capacity.

Increased susceptibility to infection

Deficiency causes:-In children:- RICKETS:- Bone softening diz.,

deformity of long bones occur.

In adults:- OSTEOMALACIA:- Bone thinning

disorder,proximal muscle weakness & bone fragility.

OSTEOPOROSIS:-Decrease bone minerilzation & inc. Bone fragility.

RICKETS:-Rickets is characterized

by bone deformities due to incomplete

mineralization, resulting in soft & pliable bones and delay in teeth

formation.The weight bearing

bones are bent to form bow

legs

Risk factors Breast-fed infants whose mothers

are not exposed to sunlight .

Breast-fed infants who are not exposed to sunlight .

Lactose intolerant.

Individuals with red hair have a decreased risk for rickets due to their greater production of vitamin D in sunlight.

In supply of 1,25 dihydroxy vit D

Absence of adequate stores

Intestinal absorption of Ca & P

Release of parathyroid hormone

25(OH) vit D

Pathogenesis of RicketsAppears to develop in 3 stages:-

1st stage

Absorption of Ca & P Mobilization of Ca & P from bone

1,25 (OH)2 vit D3

(in kidney)

2nd stage:-

Relative Hyperparathyroidism

Phosphaturia

Negative phosphorus balance

Hypophosphatemia

3rd stage:-

Relative hyperparathyroidism

Depleted 25(OH) vit D

Impaired production ofAdequate quantity of 1,25(OH)2 vit D3

Intestinal absorption of Ca & P

Signs and SymptomsBone pain or tenderness.muscle weakness ( weakness (rickety

myopathy or "floppy baby or "floppy baby syndromesyndrome")

Increased tendency for fractures (easily broken bones), especially greenstick fractures

HypocalcemiaTetany Craniotabes (soft skull) Skeletal deformity:Cranial,

spinal, and pelvic deformities

Bowed legs (genu varum)

Knock-knees (genu valgum) or "windswept knees.

Costochondral swelling ( "rickety rosary" or "rachitic rosary")

Harison’s sulcus and pot belly

Diagnosis:

Treatment:-Natural & artificial light are effective

therapeutically but oral administration preferred.

Administration of 15,000ugm or 6,00,000 IU of vit.D3 orally or I.M. induces rapid healing.

If healing lines of rickets is not seen on x-ray plate of bone within 3-4 weeks of therapy, the above dose may be repeated .

Cases who respond to this therapy are further put on 400 units or 10ugm of vitamin D3 per day after the process of healing has started.

Requirement Body needs are met entirely by

conversion of 7 dehydrocholesterol to vit D3 in skin

Or in absence of exposure to UV

light, it can be met entirely by ingestion of Vit D

The recommended dietary intake for vit D by infants has been accepted as 200IU/day

and children 400IU/day

Hypervitaminosis – DSigns & symptoms - similar to idiopathic

hypercalcemia.

Symptoms include:- Hypotonia, anorexia, irritability,

constipation, polyuria, pallorAortic stenosis, vomitingHypertensionRetinopathyUrine shows proteinuriaMetastatic calcification as revealed by

x-rays Generalized osteoporosis

T/t includes discontinuation of vit D & intake of calcium

References :-

Essential Pediatrics by O . P . Ghai

Textbook of Preventive & social medicine by K . Park

www.mc.vanderbilt.edu

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