Vitamin D (also called calciferol) is a vital dietary component. Several forms of vitamin D can be distinguished, primarily vitamin D2 (ergocalciferol) and D3 (cholecalciferol).Coming from food intake, cholecalciferol is converted in the liver to 25-OH vitamin D (synonyms: calcifediol, 25-OH-D3, 25-OH vitamin D). In the kidney, it is further converted to 1,25-dihydroxy-vitamin 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 the action of UV light (sunlight).The starting substance for the endogenous synthesis of vitamin D3 is 7-dehydrocholesterol. This provitamin is absorbed through food and subsequently converted into active vitamin D3 under the influence of UV-B light (photoisomerization) and simultaneous exposure to heat (thermoisomerization).
The process
Material required
- Blood serum
Preparation of the patient
- Not necessary
Disruptive factors
- Not known
Standard values
| Value (adult)* | Value (children) | |
| Normal range in ng/l | 16-70 | 20-84 |
* 20-29 ng/ml is considered sufficient; values above 30 ng/ml are optimal.
Indications
- Suspected vitamin D deficiency
Interpretation
Interpretation of increased values
- Alimentary (nutritional)
- Mild vitamin D deficiency (compensatory).
- Substitution with exogenous supply of calcitriol (eg, Rocatrol).
- After initiation of therapy
- In case of overdose
- Maldigestion (disorder of digestion).
- Due to chronic intestinal diseases
- Diseases
- Acromegaly (giant growth)
- Hyperparathyroidism, primary (parathyroid hyperfunction).
- Hypothyroidism (hypothyroidism)
- Lymphomas – malignant neoplasms originating from the lymphatic system.
- Rickets (type 2; vitamin D receptor defect) – form of bone softening occurring in childhood.
- Sarcoidosis – inflammatory systemic disease affecting mainly the lungs, lymph nodes and skin.
- Tuberculosis (consumption)
- Condition after kidney transplantation
- Substitution with exogenous supply of calcitriol (e.g., rocatrol).
- After initiation of therapy
- In case of overdose
- Increased demand
- 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
- Acromegaly – enlargement of hands, feet, nose and ears after completion of growth due to excessive production of growth hormones.
Interpretation of lowered values
- Alimentary (nutritional)
- Severe vitamin D deficiency
- Cadmium intoxication (poisoning with cadmium).
- Hypercalcemia (excess calcium) due to dihydrotachysterol (active ingredient from the group of vitamin D analogues used to treat hypoparathyroidism (parathyroidism) and pseudohypoparathyroidism).
- Hyperthyroidism (hyperthyroidism).
- Hypoparathyroidism (parathyroid hypofunction).
- Hypophosphatemia (phosphate deficiency) (autosomal dominant as well as X-linked (= vitamin D-resistant rickets).
- Renal insufficiency (kidney weakness).
- Pseudo-hypoparathyroidism
- Rickets (type 1; 1α-hydroxylase deficiency) – childhood-onset form of bone softening.
Other notes
- The normal requirement for vitamin D in children, adolescents and adults is 20 µg/d (= 800 IU).
Attention!Note on the state of supply (National Consumption Study II 2008)100% of children, adolescents and adults do not reach the recommended daily vitamin D intake.