Regarding vitamin D metabolism:

• A. 25-hydroxycholecalciferol is converted to 1,25-dihydroxycholecalciferol in the distal convoluted tubule of the kidney
• B. 1,25-dihydroxycholecalciferol receptors can be found in skin
• C. when calcium levels are high, 24,25-dihydroxycholecalciferol levels are also high
• D. transport in plasma is by binding to haemoglobin
• E. formation of 25-hydroxycholecalciferol is tightly regulated