Vitamin D Flashcards
Which two organs are involved in the biological active process of Vit D?
The liver where Vit D must undergo hydroxylation on cabon 25 and in the kidney on carbon 1.
What is the name of the active form of Vit D and it’s purposes?
1,25-dihydroxyvitamin D. It is necessary for bone mineralization, intestinal calcium uptake and mobilization.
What’s the name of the enzyme that produce the active form of Vit D? What factors/conditions affect this enzymes resulting in the control of active Vit D?
25-OH-D3-1 alpha-hydroxylase. Low calcium and PTH both stimulate this enzymes, whereas high P intake inhibit its activity. In addition, high levels of 1,25-dihydroxyvitamin D has a negative effect on this enzyme.
What is the primary function of Vit D?
The primary function of Vit D is to maintain Ca and P levels to support neuromuscular and bone calcification (bone hardening)
How does 1,25 dihydroxyvitamin D maintains circulating Ca and P levels within normal range?
It maintain Ca and P within normal range by:
a) Increasing intestinal absorption of Ca and P.
b) Stimulating osteoclast to mature-which breaks down bone.
c) Increasing Ca and P resorption from bone.
What are the sources of Vit D?
Fatty fish, fortified milk and breakfast cereals, sunlight, fish liver oils.
What are the DRI of Vit D?
From 14 - 50: 5mcg/d for both men/women.
From 51 -70: 10 mcg for both men/women
>70: 15/10 for men and women respectively.
True/False: Decreased serum concentration of Vit D in long-term TPN fed patients are associated with metabolic bone disease.
True
How can renal or hepatic disease result in Vit D deficiency?
In hepatic and renal disease, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D synthesis is reduced respectively resulting in Vit D deficiency. Other causes of Vit def is gastric resection and malabsorption.
What are signs of Vit D toxicities?
Hypercalcemia and hypercalcuria
What measurement is used to define Vit D deficiency?
Serum 25-hydroxyvitamin D is used to evaluate Vit D status. Serum 25-hydroxyvitamin D <80nmol/L is defined as Vit D deficiency.
When Vit D falls or during Vit D, what effect does this condition has on Ca, P and PTH?
When serum-hydroxyvitamin D falls, there’s a decrease in Ca and P levels, which stimulate PTH secretion–>acting on kidneys to produce active form 1,25-dihydroxyvitamin D.
Why 1,25-dihydroxyvitamin D (active form) is a not the best indicator for Vit D deficiency?
Because the body’s compensation to Vit D deficiency is increased renal production of the active form from PTH stimulation, the active form is usually normal or elevated during Vit D deficiency.
What levels of 25-hydroxyvitamin D is optimum for bone health and prevent chronic diseases?
78 - 100 nmol/lL.
