Vitamin D

where is vitamin D present in the body?

skin and adipose tissue(fat soluble)

the breakdown of vitamin D

ultraviolet B radiation breaks open one of the rings in a steroid alcohol present in the skin(7-dehydrocholesterol), forming vitamin D(cholecalciferol)

liver changes it into 25-hydroxyvitamin D

cells throughout the body absorb it and change that into 1,25-dihydroxy D(calcitriol)

1,25-dihydroxy D attaches itself to receptors on the DNA genes of the cell’s nucleus

circulating form of vitamin D

25-hydroxyvitamin D

active form of vitamin D

1,25-dihydroxy D(calcitriol)

what class of chemical is vitamin D?

seco-steroid: steroids in which one of the rings has been broken(9,10 C-C bond in ring B is broken)

what does vitamin D do?

dietary absorption of calcium and phosphorus, bone health, activates the genes that control cell growth and apoptosis, neuromuscular and immune function, reduction of inflammation, release of neurotransmitters

lack of vitamin D

rickets, infections(flu A and B), autoimmune diseases, CV disease, cancers

how do we get vitamin D?

natural sunlight, oily fish, fortified foods

symptoms of vitamin D deficiency

fatigue, depression, poor concentration, arthritis, weakness

half life of 25(OH)

10 weeks

two major types of vitamin D

vitamin D2(ergocalciferol): synthesized by plants, not produced by the human body

vitamin D3(cholecalciferol): made in large quantities in the skin when sunlight strikes bare skin, also ingested from animal sources

what type of test do we use to detect?

chemiluminescent microparticle immunoassay(CMIA) of 25-hydroxyvitamin D

specimen requirements

serum must be separated from gel or cells within 72 hours, refrigerate up to 12 days, frozen for longer

reference ranges for vitamin D

optimal: 30-96ng/mL

under 18: no established reference range

signs of vitamin D intoxication

vomiting, anorexia, heart arrhythmias, constipation, weight loss, kidney failure, calcification of arteries

as you get older you need _____ sun exposure

more

vitamin D3 has a half life of how long

10 weeks

vitamin D2 has a half life of how long

2 weeks