Vitamin D

Introduction

• It is a fat soluble vitamins• Sometimes called a hormone or the sunshine vitamin• the body can usually manufacture the vitamin it needs

if exposed to enough sunlight• When the body is exposed to sun light (UV light), 7-• When the body is exposed to sun light (UV light), 7-

dehyderocholestrol present under the skin will bechanged into cholecalciferol which is carried to theliver for hydroxylation on the 25th carbon to form 25-hydroxy cholecalciferol that is further carried to thekidney for hydroxylation to form 1,25,dihydroxycholecalciferol (active form of vit. D)

Physiology

Cont…

• Being a fat-soluble vitamin, it helps in calcium absorption from the intestines, calcium resorption from the bone, and calcium deposition into osseous tissue. Its active metabolites are produced in two tissues, but metabolites are produced in two tissues, but have their effects on other tissues, just like other hormones. They also, like other hormones, have a feedback mechanism that controls the rate of synthesis and secretion of its active form.

Cont…

• The two most important types are D-2 (ergocalciferol) and D-3 (cholecalciferol). Vitamin D-2 exists in fungi and yeast and is the form generally added to milk, food, and form generally added to milk, food, and vitamin supplements. It is the form used to combat hypocalcaemia. Vitamin D-3 is found in fish oils and milk.

Causes of Vitamin D deficiency and itspredisposing factors

• The major cause is inadequate intake ofvitamin D.

• Smog, smoke, dust, dark city streets, shade,clothing, extremely black skin color, and aclothing, extremely black skin color, and alargely indoor lifestyle are some of the factorsthat may prevent vitamin D absorption formthe sun

• These factors may lead to a deficiency unlessvitamin D is found elsewhere in the person'sdiet

Consequences

• VD deficiency manifest as rickets in children and growing animals while in adults manifests as osteomalcia

• Its clinical significance is mainly due to the • Its clinical significance is mainly due to the impact of the disease that it has on child health in general

Rickets:• Abnormalities of the weight bearing bones and is

associated with bone pain, muscular tenderness, & hypocalcemic tetany:

• Rachitic bones cannot withstand ordinary stresses and strains resulting in the appearance of and strains resulting in the appearance of bowlegs, knock knees, beaded ribs, pigeon chest, frontal bossing of the skull, delayed Fontanel closure, craniotabes and late teeth development; Enlarged wrist and anklebones (double maleolus).

• Developmental delay is commonly observed finding

Osteomalacia:

• Pain in ribs, lower spine, pelvis & legs, muscle weakness & spasm, brittle, easily broken bones and muscle diseases

• Apart from its long-term health consequences • Apart from its long-term health consequences such as deformity,VDD can also contribute to child morbidity & mortality.

Osteoporosis:

• It is frequently confused with osteomalacia; however, it is a very different disease of a bone.

• It involves diminished bone mass with the retention of normal histological appearance.

• It is associated with aging• It is associated with aging• It is a multifactorial disease involving impaired

vitamin D metabolism and low estrogen levels • The most common bone disease of the

postmenopausal women and also occurs in older men

Sources:

There are five major common sources of vitamin Dlisted as follows:

• Sardines,• Cold liver oil,• Fresh water fish,• Fresh water fish,• Fortified milk, and Chicken livers.With the exception of milk, these are all natural

sources of vitamin D.Note: One half teaspoon of cod liver oil or two cups

of vitamin D-fortified milk provide all the vitaminD an average adult needs daily.

Functions:

• Vitamin D has essential metabolic roles in themaintenance of calcium and phosphoroushomeostasis and cell differentiation as shown inthe figure below;

• In the bone: it functions in conjunction with PTHand estrogen to regulate the mobilization andand estrogen to regulate the mobilization anddeposition of calcium and phosphorous, preventsrickets

• In the kidney: it increases renal tubular re-absorption of calcium and phosphate.

• In addition the vitamin is known to regulate over50 genes in the body

Global status of Vitamin D deficiency

• Historically victims of rickets have been poor children in industrialized cities where exposure to sunlight is limited

• Rickets continues to be a significant public • Rickets continues to be a significant public health problem in china and pockets have been identified in Nigeria and Bangladesh

National status

• In Ethiopia, The prevalence of vitamin D deficiency, which was earlier reported to be around 30%, has remained at that level over the years

• The most affected groups in the country are • The most affected groups in the country are children aged 3 mo-3 years. The deficiency state usually occurs in association with PEM, diarrhea and pneumonia

• A retrospective review made in Jimma hospital indicated the problem to exist in 7% of preschoolers

Investigations:

• Serum Vitamin D (Decreased)• Serum calcium (Decreased)• Serum phosphate (Decreased)• Alkaline phosphatase(Increased)• Alkaline phosphatase(Increased)• Urinary hydroxyproline (Increased)• PTH (Increased)• Bone X-ray.

RDA:

Age:0-6 months 7.5 mcg6-12 months 10mcg1-10 years 7.5mcg1-10 years 7.5mcgMales:11-24 years 10mcg25+ 10mcg

Cont…

• Too much vitamin D can be toxic resulting innausea, vomiting, diarrhea, polyuria,headaches, and renal damage.

• Soft tissues like heart, blood vessels, lungs,and stomach may harden because too muchand stomach may harden because too muchcalcium, manufactured as a result of too muchvitamin D.

• These symptoms have been reported to occurafter a prolonged intake of over 2000 IU perday in an adult

Control and preventions

• Vitamin D supplements• Exposure to sunlight• Fortification• Fortification• Nutrition education