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Continuing Medical Education (CME) for Vitamin D includes genes and questions – July 2014

Vitamin D’s Role in Health — Deterministic or Indeterminate?

By Stephanie Dunne and Jenna A. Bell, PhD, RD
Today’s Dietitian Vol. 16 No. 7 P. 48

See also VitaminDWiki

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Gene Enzyme Location Conversion
CYP27A1 Vitamin D-25-hydroxylase Liver Vitamin D2 or D3 à calcidiol [25(OH)D]
CYP2R1 Vitamin D-25-hydroxylaseLiverVitamin D2 or D3 à calcidiol [25(OH)D]
CYP27B125-hydroxyvitamin D
Kidney and
other tissues
Activation: Calcidiol [25(OH)D] à
calcitriol [1alpha,25(OH)2D]
CYP24A125-hydroxyvitamin D-24-
Kidney and other
Inactivation: Calcitriol or calcidiol à
24,25(OH)2D or calcitroic acid

10 multiple choice questions

1. Vitamin D is considered to be which of the following?

a. Vitamin
b. Hormone
c. Prohormone
d. Antioxidant

2. Which of the following genetic mutations can result in normal levels of
25-hydroxyvitamin D [25(OH)D] and low levels of 1alpha,25(OH)2D?

a. CYP27A1
b. CYP27B1
c. CYP2R1
d. CYP24A1

a. People with liver failure
b. People who live north of 45˚N latitude
c. All adults older than 65
d. Everyone

4. Which of the following is the active form of vitamin D in the body?

a. Calcitroic acid
b. Calcidiol
c. Calcitriol
d. 24,25(OH)2D

5. Beyond bone health, vitamin D seems to help maintain health in which of the following ways?

a. Maintaining kidney function
b. Supporting muscle growth
c. Promoting weight loss
d. Suppressing the autoimmune response

6. Which of the following foods has the highest content of vitamin D per serving?

a. Cod liver oil
b. Sun-dried mushrooms
c. Swordfish
d. Fortified skim milk

7. The sun is too low during the winter months to produce any vitamin D
in the skin above and below which north/south parallel?

a. 20˚
b. 33˚
c. 40˚
d. 52˚

8. Vitamin D is associated with bone health because it does which of the following?

a. Stimulates osteoblasts
b. Increases phosphorus excretion
c. Reduces parathyroid hormone release
d. Increases calcium absorption from the intestine

9. The Institute of Medicine identifies vitamin D deficiency
as serum calcidiol levels below which of the following levels?

a. 15 nmol/L
b. 20 nmol/L
c. 32 nmol/L
d. 50 nmol/L

10. Each serving of foods fortified with vitamin D contain approximately which of the following amounts?

a. 2.5 mcg (100 IU)
b. 25 mcg (1,000 IU)
c. 40 mcg (1,600 IU)
d. 100 mcg (4,000 IU)
