Abstract: Methods for diagnosing, treating, and preventing catabolism-related vitamin D deficiency and related disorders; related compositions, apparatus and kits, are disclosed. A method involves measuring CYP24 expression and/or activity, or a proxy thereof such as FGF23 level, in a patient and correlating abnormally elevated CYP24 expression and/or activity with catabolism-related vitamin D deficiency or with susceptibility for catabolism-related vitamin D deficiency. In response to abnormally elevated CYP24 expression and/or activity, the method further includes administering a CYP24 inhibitor to the vitamin D deficient or at-risk patient, and preferably avoiding activation of the vitamin D binding receptor, such as by avoiding administration of active vitamin D compounds to such patients. Optionally, a vitamin D prohormone or prohormone can be administered.

Abstract: The invention relates to methods and compositions for reducing toxicity associated with administration of vitamin D3, its 25-hydroxylated and 1-hydroxylated forms, and analogs thereof.

Abstract: The a method of treating elevated blood levels of iPTH by increasing or maintaining blood concentrations of both 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D in a patient by administering, as necessary, both Vitamin D repletion and Vitamin D hormone replacement therapies, is disclosed. The blood concentrations of 25-hydroxyvitamin D are increased to and maintained at or above 30 ng/mL, and blood concentrations of 1,25-dihydroxyvitamin D are increased to or maintained within a patient's normal historical physiological range for 1,25-dihydroxyvitamin D without causing substantially increased risk of hypercalcemia, hyperphosphatemia or over suppression of plasma iPTH in the patient. The blood levels of 25-hydroxyvitamin D are maintained at or above 30 ng/mL between doses of Vitamin D repletion therapies, and the blood levels of 1,25-dihydroxyvitamin D are maintained in the patient's normal historical physiological range between doses of Vitamin D hormone replacement therapies.