25-Hydroxy Vitamin D

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:

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
  • 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.