25-Hydroxy vitamin D (synonyms: calcifediol, 25-OH-D3, 25-OH vitamin D) is a vitamin that regulates calcium and phosphate balance. Regulation of calcium and phosphate balance:
- Intestine (calcium and phosphate absorption).
- Kidneys (calcium and phosphate reabsorption).
- Bones (mobilization of calcium and phosphate with the participation of parathyroid hormone and calcitonin).
Coming from food intake, cholecalciferol is converted in the liver into 25-OH vitamin D (synonyms: calcifediol, 25-OH-D3, 25-OH vitamin D). In the kidney, it is further converted to 1,25-dihydroxyvitamin D (synonyms: calcitriol, 1α-25-OH-D3 ), the biologically active form of vitamin D. Endogenously, 1,25-di-OH-cholecalciferol (vitamin D3) is formed from 7-dehydroxycholesterol under UV light action (sunlight). Endogenously, cholecalciferol (vitamin D3) is formed from 7-dehydroxycholesterol under UV light action (sunlight). The body’s vitamin D content can be determined by determining 25-OH vitamin D.
The procedure
Material needed
- Blood serum → be sure to store away from light.
Preparation of the patient
- Not necessary
Disruptive factors
- None known
Standard values
Standard values in μg/l | |
Infants | 20-135 |
Children in summer | 24-144 |
Children in winter | 12-60 |
Adults in summer | 20-120 |
Adults in winter | 10-50 |
Optimal | 30-70 µg/l |
In dialysis patients | Target value > 30 µg/l (K/DOQI guidelines). |
25-Hydroxyvitamin D (25-OH vitamin D) and health status
nmol/l2 | μg/l | Health status |
< 30 | < 12 | Vitamin D deficiency, causes rickets in infants and children and osteomalacia (softening of bones) in adults |
30-50 | 12-20 | Generally considered insufficient with respect to bone health in healthy individuals |
≥ 50 | ≥ 20 | Generally considered sufficient with respect to bone health in healthy individuals |
> 125 | > 50 | Potential adverse effect, especially from > 150 nmol/l (> 60 µg/l) |
2 1 nmol/l = 0.4 µg/l = 0.4 ng/ml
Indications
- Suspected bone metabolism disorders with increased bone resorption.
- Therapy control in bone metabolism disorders with increased bone resorption.
- Vitamin D supply
Interpretation
Interpretation of increased values
- Drug therapy with vitamin D
- Strong sun exposure
Elevated levels can lead to hypervitaminosis, with nausea/vomiting, appetite disturbances and calcium deposition in vessels. Interpretation of decreased values
- Alimentary (nutritional)
- Unbalanced diet, etc.
- Malnutrition / malnutrition
- Vegetarian
- Malabsorption (disorder of absorption)
- Due to chronic intestinal diseases – for example, in celiac disease (leading symptoms: Weight loss, meteorism (flatulence) and diarrhea) etc.
- Digestive insufficiency
- Maldigestion (disorder of digestion).
- Due to chronic intestinal diseases
- Diseases
- Hepatitis (inflammation of the liver)
- Liver cirrhosis (liver shrinkage; in this process, liver tissue is destroyed and permanently transformed into scar tissue and connective tissue)
- Renal insufficiency (kidney weakness)
- Women with postmenopausal osteoporosis (bone loss after menopause).
- Medication
- Taking antiepileptic drugs (medications that act against seizures) – such as phenytoin and diphenylhydantoin, and barbiturates.
- Increased need
- Growth/children
- Pregnancy/breastfeeding phase
- Older women respectively men (≥ 65 years)
- Insufficient UV-B exposure (winter months, people who are bedridden for long periods of time or spend little time outdoors or have a lack of sunlight or use sunscreens extensively).
- Colored
Decreased levels can lead to hypovitaminosis, which manifests itself via rickets (bone softening in childhood) and osteomalacia (bone softening in adulthood). Vitamin D is fat soluble. It can be stored in hormone-producing organs such as the adrenal cortex, and these stores then have reserves for a few weeks. Vitamin D is found mainly in fish (liver oil), eggs, butter, milk, as well as in animal tissues. The following requirement values for vitamin D intake apply (according to DGE):
Standard values in μg/die1 | |
Children and adults (under 65 years) | 20 |
Adults (65 years of age and older) | 20 |
Pregnant and breastfeeding women | 20 |
Mature newborns (prophylaxis). | 10 |
11 μg = 40 IU In adults, the daily requirement can be met by sufficient sun exposure (20 cm² skin for 1 hour) alone.