| Vitamin D Replacement
| Osteomalacia-Rickets-Vitamin D
| Vitamin D resistant rickets
| Vitamin D (25 OH D) Testing
| X linked Hypophosphataemic rickets
Serum 25(OH)D concentration is an indicator of exposure to vitamin D (from skin synthesis
and dietary intake). It is recommended that the serum 25(OH)D concentration of all individuals in the UK should not fall below 25 nmol/L at any time of the year. Adequate dietary calcium is necessary for a clinical response to Vitamin D
- A group of steroid hormones regulating body levels of calcium and phosphorus
- Induction of cell differentiation, inhibition of cell growth
- Immunomodulation, and control of other hormonal systems.
- Ergocalciferol D2 may be used as a vitamin D supplement
- Cholecalciferol D3 is generated in the skin from 7-dehydrocholesterol when exposed to ultraviolet light.
- Both are prohormones that need two hydroxylations to become active
- These are done in the liver and then the kidney
- Vitamin D "Calciferol" (ergocalciferol-D2, cholecalciferol-D3, alfacalcidol)
- Kidney 1-hydroxylation: by 1-alpha-hydroxylase, yielding 1,25-dihydroxycholecalciferol the biologically active form [Tightly regulated by Parathyroid hormone] also called Calcitriol 1 (OH) Vitamin D
- Liver 25-hydroxylation: cholecalciferol is hydroxylated to 25-hydroxycholecalciferol by the enzyme 25-hydroxylase 1,25(OH) Vitamin D which is carried bound to vitamin D-binding protein
- Vitamin D hormone activates its cellular receptor (vitamin D receptor or VDR), which alters the transcription rates of target genes responsible for the biological responses.
- Binds intracellular receptors and modifies gene expression
- Receptor has a very high affinity for 1,25(OH)2 D
- Increases intestinal absorption of calcium, phosphate and magnesium ions
- In bone provide the proper balance of calcium and phosphorus to support mineralization.
- Increases reabsorption of phosphate in the kidney
Vitamin D deficiency : Rickets/Ostemalacia
- Result is a failure of osteoid to calcify in adults is called osteomalacia
- Poor dietary intake or malabsorption
- Poor sunlight exposure
- Vitamin D binders in food
- Vitamin D resistant rickets
- A 25-OHD = 30 nmol/L suggests deficiency
- A 25-OHD 30-50 nmol/L suggests possible deficiency
- The new advice from PHE is that adults and children over the age of one should consider taking a daily supplement containing 10mcg of vitamin D, particularly during autumn and winter.
- People who have a higher risk of vitamin D deficiency are being advised to take a supplement all year round.
- Consider at-risk groups include people whose skin has little or no exposure to the sun, like those in care homes, or people who cover their skin when they are outside.
- People with dark skin, from African, African-Caribbean and South Asian backgrounds, may also not get enough vitamin D from sunlight in the summer. They should consider taking a supplement all year round as well.
- Check BNF Cholecalciferol (D3)
- Prevention of vitamin D deficiency: Cholecalciferol (D3)400 units daily.
- Treatment of vitamin D deficiency:Cholecalciferol (D3) 800 units daily
- Higher doses may be necessary for severe deficiency.
- Check BNF Ergocalciferol (D2)
- Malabsorption or liver disease: Ergocalciferol (D2) 40,000 units daily
- Hypocalcaemia of hypoparathyroidism to achieve normocalcaemia: Ergocalciferol (D2) 100,000 units daily.
- Prevention of vitamin D deficiency: Ergocalciferol (D2) 400 units daily.
- Treatment of vitamin D deficiency: Ergocalciferol (D2) 800 units daily or higher
- Check Alfacalcidol in BNF
- Patients with severe renal impairment requiring vitamin D therapy
- Treatment: Alfacalcidol 0.5-1 microgram OD adjusted to avoid hypercalcaemia
- Maintenance: Alfacalcidol 0.25-1 microgram OD adjusted to avoid hypercalcaemia