1Vitamin - D (antirachitic vitamin) BY R.PARTHSARATHY
2 Introduction Vitamin D is a steroid. It is present in animals, plants and yeast. Insoluble in water, soluble in fat and organic solutions. Sensitive to oxygen, light and iodine. Heating and mild acidity can convert into inactive form.
3Chemical structureMOST IMPORTANT FORMIt is considered asprohormone.BECAUSEFrom which1,25-dehydrocholesterolsynthesized. (active form)
5Sources Liver and viscera of fish. Liver of animals which feeds on fish. Eggs, butter and milk. But the cheapest is the sunlight.
6 Functions Vitamin D acts on organs such as bone, kidneys, intestinal mucosa for regulation of calcium and phosphorus metabolism. It promotes intestinal absorption of calcium and phosphorus. It promotes bone resorption and calcium mobilization to increase the levels of calcium and phosphorus.(PTH) Mineralization of bone is promoted by 1,25-dihydroxy D3. It is necessary for the development of bones and normal growth of the body. It also increases the citrate level of blood, bone, kidneys and heart tissues.
8Daily requirements Children and infants : 400IU/day Adults : 200IU/day Plasma concentration of 25-OH D3 Average 25-30 ng/mL Range 8 - 60 ng/mL Levels < 10 ng/mL indicative of deficiency Levels > 150 ng/mL associated with toxicity
9 Deficiency manifestations Deficiency of vitamin D produces rickets in growing children with characteristic defects in bone growth. Deficiency of vitamin D in adults is called osteomalacia which is characterized by - poor intestinal absorption of calcium and phosphorus. - rise in urinary phosphorous. - negative calcium balance. - muscular weakness and early fracture of bone. - loss of calcium and bowed legs.
10Deficiency manifestations Pigeon’s chest Bowed legs
11Toxicity Vitamin D is fat soluble, and accumulation (from diet) in the body can be toxic. The long-term safe dose of vitamin D is not known, however, 10,000 IU /day is safe in healthy adults All known cases of vitamin D toxicity have involved intake of or over 40,000 IU/day. The LD50 in man is unknown – there are no reported deaths from acute toxicity.
12 Hyper-vitaminosis Excess of vitamin D causes toxicity characterized by Nausea Anorexia Digestive disturbances and calculi formation. Elfin facies
13 Factors that influence vitamin D status Genetics Vitamin D resistant rickets (hypophosphatemic rickets) Vitamin D dependent rickets (type I) Vitamin D dependent rickets (type II) Drugs Anticonvulsant drugs such as Diphenylhydatoin, phenobarbital Alcohol low 25(OH)D level Age Low epidermal con of 7-dehydrocholesterol 1-hydroxylase: less responsive to PTH Sex