1. VITAMIN D
Dr SIVARAJ S
DEPT OF PHYSIOLOGY
ALL INDIA INSTITUTE OF MEDICAL SCIENCES
NEW DELHI

2.  Known as the “Sunshine
vitamin”
 Can be produced in the
body, has specific target
tissues
 Dietary requirement is
not essential

3.  Sources sources of vitamin
 Major source synthesis in the D3, providing only 0.4 to 1
skin ultraviolet B (wavelength mcg/L.
290–315 nm)
 Vitamin D3 exists naturally in
animal products, and the
richest sources are fish liver
oils
 Except for fish, food (unless
fortified) contains only limited
amounts of vitamin D
 Vitamin D2 (ergocalciferol) is
obtained from plant sources
and is the chemical form
found in some supplements.
 Human milk and unfortified
cow's milk tend to be poor

4.  Absorption, Transport and Storage
Vit D+other lipids
Micelles
Incorporated into chylomicrons
Plasma
Chylomicron remnants or DBP
Liver peripheral tissue

5. VitaminD3
Vit D 25 Hydroxylase

6.  Functions
 Maintenance of calcium and phosphorus
homeostasis
 Gene expression
 In the bone PTH alone or with
calcitriol, estrogen, or both, moves calcium and
phosphorus from the bone to maintain normal blood
levels
 In the kidney calcitriol increases renal tubular
reabsorption of calcium and phosphate.These
activities are coordinated with the purpose of
maintaining plasma calcium concentrations within a
narrow range.

8.  RDA
 The AI increases to 10 mcg/day(400IU) for adults
age 5l years and older and increases even more to
15 mcg/day( 600IU) for adults 71 years and older
 The UL for vitamin D for infants is 25 mcg/day
(1000 IU) and for children and adults,50mcg/day
(2000 IU)

10.  Deficiency
 Risk factors
• Old age
• Lack of sun exposure,
• Dark skin
• Fat malabsorption
• Obesity
Rickets Osteomalacia
In children in adults

11.  Rickets
 Impaired mineralization of growing bones
 Involves Ca Phosphorus and Vitamin D
 Clinical features
• Bone pain, muscular tenderness, and
hypocalcemic tetany
• Bowed legs, “knock knees," beaded ribs (the
rachitic rosary), pigeon breast, and frontal
bossing of the skull
 Radiology
• Enlarged epiphyseal growth plates
 Treatment
 Rickets caused strictly by vitamin D deprivation
can be treated effectively with oral preparations
of the vitamin or natural sources rich in the
vitamin

12.  Osteomalacia
 Involves generalized reductions
in bone density and the presence
of pseudofractures, especially of
the spine, femur, and humerus
 Clinical features
• Muscular weakness and bone
tenderness
• Greater risk of
fractures, particularly of the wrist
and pelvis
 Prevention
 Possible with adequate
consumption of vitamin D

13.  Toxicity
• Infants and small children are most susceptible to hypervitaminosis D
• The UL for vitamin D is 25 mcg (1000 IU)/day for infants and 50 mcg (2000
IU)/day for children and adults.