Methods useful for vitamin D deficiency and related disorders

A method of diagnosing and treating catabolism-related vitamin D deficiency or a susceptibility thereto in a patient having Chronic Kidney Disease, comprising:

• requesting a test providing the results of a measurement, direct or indirect, of a patient's CYP24 expression and/or activity, wherein abnormally elevated CYP24 expression and/or activity indicates a susceptibility for catabolism-related vitamin D deficiency, wherein the test comprises measuring the level of fibroblast growth factor 23 (FGF23) in the patient as a proxy for the level of CYP24 expression and/or activity, wherein a level of FGF23 greater than the upper value of the normal range indicates abnormally elevated CYP24 expression;
• and
• administering an effective amount of a pharmaceutically acceptable formulation comprising a CYP24 inhibitor to the patient in response to abnormally elevated CYP24 expression and/or activity to treat or prevent catabolism-related vitamin D deficiency defined as a total serum level of 25-hydroxyvitamin D below 30 ng/mL.