• DOI:10.1007/BF02509538
• Corpus ID: 35887181

Assessment of vitamin D nutritional and hormonal status: What to measure and how to do it

@article{Hollis2006AssessmentOV,
  title={Assessment of vitamin D nutritional and hormonal status: What to measure and how to do it},
  author={B. W. Hollis},
  journal={Calcified Tissue International},
  year={2006},
  volume={58},
  pages={4-5}
}

• B. Hollis
• Published 2006
• Medicine
• Calcified Tissue International

The metabolism and mechanism of action of vitamin D has been studied and elucidated quite extensively during the past 25 years. During this period, many metabolites of vitamin D have been identified and many of them subsequently quantitated in the circulation. With all of this information available, what is the physician to do when faced with the problem of which vitamin D metabolite to assess in the circulation in a given clinical circumstance? First, there are four quantitatively significant vitamin D metabolites in the human circulation that have been extensively investigated. These are the parent compound vitamin D 25-hydroxyvitamin D [25(OH)D], 24,25-dihydroxyvitamin D [24,25(OH)2D], and 1,25-dihydroxyvitamin D [1,25(OH)zD]. Of these four metabolites, extensive research has shown only two, 25(OH)D and 1,25(OH)2D, to provide any real clinically relevant information following their assessment in the circulation. So the real question arises, Which vitamin D metabolite, 25(OH)D and/or 1,25(OH)2D should be assessed in a given clinical circumstance when the physician suspects a problem with the pat ient 's calcium metabolic system? Many clinicians will routinely order a test for circulating 1,25(OH)zD no matter what the clinical problem because they have been taught or have read that 1,25(OH)zD is the active form of vitamin D. Thus, it must be the metabolite to measure if one wishes to obtain a vitamin D measurement. In my own experience, I have encountered countless times when a clinician orders a test for circulating 1,25(OH)zD. I usually inquire why they have requested this measurement and their response is usually "To determine if the patient has adequate vitamin D status ." This response confirms to me that the clinician is misinformed about what measurement he or she requires. Thus, under what clinical conditions should 1,25(OH)zD and/or 25(OH)D be assessed in the human subject? In my opinion, determination of circulating 1,25(OH)zD, at this stage of our clinical knowledge, has very limited clinical utility. Circulating 1,25(OH)zD is diagnostic for several clinical conditions, including vitamin D-dependent rickets types I and II, hypercalcemia associated with sarcoidosis, and other hypercalcemic disorders caused by increased values. These other d isorders include tuberculos is , fungal infect ions, Hodgkin 's disease, lymphoma, and Wegener 's granulomatosis. In all other clinical conditions involving the vitamin D endocrine system, including hypoparathyroidism, hyperpara thyroidism, and chronic renal failure, the assay of 1,25(OH)zD is a confirmatory test. As a result, except in these few rare ins tances , m e a s u r e m e n t of c i rcula t ing 1,25(OH)zD provides very little clinically relevant information. I t is also impor tant to r emember that circulating 1,25(OH)zD provides essentially no information with respect to the pat ient 's nutritional vitamin D status.