Vitamin D Regulation, Clinical Significance and Treatment (by ASCLS) (Online Course)

Hershel Raff, PhD; Professor of Medicine, Surgery, and Physiology, Medical College of Wisconsin; Research Director and Clinical Supervisor, Endocrine Research Laboratory, Aurora St. Luke's Medical Center

Course provided in partnership with the American Society for Clinical Laboratory Science (ASCLS).

Vitamin D testing has become much more common, however which form to measure can be confusing to patients and their physicians. This presentation will help the laboratorian become more familiar with and knowledgable about Vitamin D.

Participants will learn the synthetic pathway, regulation and metabolism of Vitamin D. Vitamin D plays an important role in the regulation of calcium, so an overview of the integrated control of calcium and PTH metabolism will be also presented. Conditions and effects of deficiency & insufficiency of Vitamin D will be presented along with common forms of treatment/supplementation.

Several lab tests exist to measure various forms of Vitamin D. Which is most appropriate and why as well as comparison of available methods will be reveiwed. The course concludes with a case study to illustrate the usefulness of Vitamin D testing. See the table of contents below.

Online screens are easy to navigate and a table of contents is available to help return to previous information. Learn at your own pace – the online system automatically bookmarks progress - resume at any time, from any computer.

Earn 1 hour of P.A.C.E.® - credit after viewing the course and successfully completing a quiz. Instructions to print a P.A.C.E.® certificate from the ASCLS CE Organizer will be provided.

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Continuing Education Credits


  • Explain the integrated control of calcium balance involving parathyroid hormone (PTH) and vitamin D.
  • Explain the vitamin D synthetic pathway that leads to the production of 25-hydroxyvitamin D (25(OH)D) in the liver (unregulated step) and 1,25(OH)2D (active form) produced in the kidney by 1-hydroxylase (regulated step).
  • Describe the difference between vitamin D deficiency and insufficiency.
  • Discuss the appropriate serum measurement to assess vitamin D status.
  • Identify and discuss the established and proposed effects of vitamin D deficiency and insufficiency.
  • Discuss the approaches to vitamin D supplementation.

Course Outline

  • Calcium Balance
      • Everything Starts with Calcium!
      • Calcium Balance
  • Regulation of Parathyroid Hormone Release
      • Regulation of Parathyroid Hormone Release
  • Vitamin D metabolism and the physiological effects of 1,25(OH)2vitamin D (called 1,25(OH)2D from here on).
      • Vitamin D metabolism and the physiological effects of 1,25(OH)2vitamin D (called 1,25(OH)2D from here on).
  • Clinical Assessment of Vitamin D Status
      • Clinical Interpretation of Serum Vitamin D Metabolites
      • Measurement of Serum 25(OH)D
      • Measurement of 25(OH)D2 and 25(OH)D3 by LC-MS/MS
      • Comparison of Immunoassay and LC-MS/MS
  • Vitamin D Deficiency
      • Causes of Vitamin D Deficiency
      • Stages of Vitamin D Deficiency
      • The Vitamin D deficiency controversy.
    • Effects of Vitamin D Deficiency and Insufficiency
      • Fracture Risk
      • Many other effects have been proposed
      • Cardiovascular Risk
      • Mortality
      • Asthma in Children
      • Type 2 Diabetes Mellitus
      • Summary of Effects
  • Vitamin D Supplementation
      • Sources of Vitamin D
  • Treatment of Vitamin D Deficiency
      • Treatment Paradigm
      • Vitamin D supplementation – which is better, D2 (ergocalciferol) or D3 (cholecalciferol)?
    • Institutes of Medicine Report
      • Summary of IOM Report
      • Institutes of Medicine Report
  • Vitamin D Intoxication
      • Vitamin D Intoxication – Is it really a concern?
  • Case Study
      • Case Study
      • Case Resolution
  • Summary
      • How to get enough vitamin D
      • Summary
  • References
      • References

Control of parathyroid hormone release

Vitamin D metabolism and effects