Vitamin D, also known as the sunshine vitamin, can be produced in the skin upon exposure to UVB light or obtained in the diet. It plays an important role in calcium and phosphorus homeostasis. Dietary requirements are minimal as the body can produce vitamin D3 in the skin, but certain groups like the elderly are at higher risk of deficiency. Deficiency can lead to rickets in children and osteomalacia in adults, characterized by soft, weak bones and bone pain.

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.