• J Bone Miner Metab. 2008;26:603-608: In the short term, a single 300 000 IU oral dose of vitamin D(3) was more effective than 800 IU per day to increase serum 25(OH)D levels in elderly persons, living in a low-income housing unit, who were taking 500 mg elementary calcium supplement per day.
• J Clin Endocrinol Metab. 2008 Aug;93(8):3015-20: Cholecalciferol is almost twice as potent as ergocalciferol in increasing serum 25(OH)D, when administered either by mouth or im. 25(OH)D plays a role in modulating serum PTH.
• http://www.bmj.com/cgi/reprint/339/oct01_1/b3692.pdf; Reduction of falls with Vit D supplementation
  

Osteomalacia

Vitamin D Deficiency

• Review NEJM'07 [ pdf ]: treatment of deficiency: eg 50,000IU D2 weekly x 8wk[-16wk if D<30ng/mL] (or 1,000IU D3/d or 3,000IU D2/d)
• Causes of VDD

• Dcrd skin synthesis: sunscreen, pigment, aging, season
• Dcrd bioavailabilitity: malabsorption, obesity (sequestration in fat)
• Icrd catabolism: anticonvulsants, glucocorticoids, HAART, antirejection medication
• (infants: Breast feeding: poor VD content in human milk)
• Dcrd synthesis of 25-OH-D: liver failure
• Icrd urinary loss of 25-OH-D: nephrotic syndrome
• Dcrd synthesis of 1,25-(OH)2-D: CKD via hyperphosphataemia and FGF23, and dcrd synthesis
• Heritable disorders--rickets: VDDR-{T1: dcrd 1,25 synthesis|T2: resistance to 1,25|T3: target-cell resistance}, {AD|XL}-hypophosphataemic rickets (:phosphaturia dcrs 25OHD-1alpha-OHase activity)
• Acquired disorders:  Tu-induced osteomalacia (FGF23+-other phosphatonins), Primary HPTH, granulomatous disorders/some lymphomas, hyperthyroidism

Vitamin D (http://www.bnf.org/)

• ergocalciferol (calciferol, vitamin D2)
• colecalciferol (vitamin D3)
• dihydrotachysterol
• alfacalcidol (1alpha-hydroxycholecalciferol)
• calcitriol (1,25-dihydroxycholecalciferol)