00:01 Let’s take a look at Vitamin D pathologies. 00:05 Begin by discussion of Vitamin D by looking at the different ways in which Vitamin D is provided to us in the active form. 00:14 Vitamin D can be taken up by food; Vitamin D can come from the skin with the help of UV light. 00:24 Rarely can Vitamin D deficiency take place in developed countries through dietary deficiency, but it could very much occur with lack of exposure to the sun. 00:37 This then gets into circulation, but this would be the inactive form. 00:41 The first place that it goes to would be to the liver and at the site of liver, it gets 25-hydroxylated. 00:49 This is the major circulating type of Vitamin D, 25-hydroxylated Vitamin D will then turn down to the kidney. 00:58 Here, with the help of 1-alpha-hydroxylase, because of PTH working upon it will stimulate the 1-alpha-hydroxylase resulting in the active compound of calcitriol or 1,25 dihydroxycholecalciferol. 01:11 The actions of this on the intestine… remember that Vitamin D is lipid soluble… the lipid soluble vitamins are ADEK… A, D, E, K. 01:24 The D, Vitamin D, will pass through the membrane, act upon the nucleus and so, therefore, bring about transcription/translation where you can then reabsorb your calcium from the intestine and Vitamin D works upon the kidney to reabsorb both calcium and phosphate whereas PTH only reabsorbs calcium. 01:47 Production effects of Vitamin D 1,25 dihydroxycholecalciferol reabsorbs your calcium. 01:54 Unlike PTH, Vitamin D does not promote renal phosphate wasting. 01:58 In fact, it promotes reabsorption.
The lecture Vitamin D Deficiency: Vitamin D Production and Effects by Carlo Raj, MD is from the course Parathyroid Gland Disorders.
The activation of vitamin D requires which enzyme and what is the action of this enzyme?
What is the most common form of vitamin D found in circulation?
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Thank you so much for this beautiful lecture. It will help us so much