7-Dehydrocholesterol
Overview
7-Dehydrocholesterol is a sterol precursor in the cholesterol biosynthesis pathway and the immediate precursor to vitamin D3 in skin upon ultraviolet B exposure. It accumulates in Smith-Lemli-Opitz syndrome (SLOS) due to 7-dehydrocholesterol reductase (DHCR7) deficiency, impairing cholesterol synthesis and causing characteristic developmental abnormalities. Elevated plasma levels indicate SLOS, while normal levels help exclude this diagnosis; low levels have no established clinical significance. Clinically, 7-dehydrocholesterol measurement confirms SLOS diagnosis, differentiates it from other teratogenic syndromes, and supports newborn screening follow-up.
Clinical Use Cases
- Diagnostic confirmation of Smith-Lemli-Opitz syndrome.
- Newborn screening follow-up for suspected SLOS.
- Evaluation of dysmorphic features and developmental delay.
- Genetic counseling for families with SLOS-affected children.
- Monitoring cholesterol supplementation therapy response.
Specimen Types
- Plasma.
- Serum.
- Amniotic fluid (prenatal diagnosis).
- Cultured fibroblasts.
Measurement Methods
- Gas chromatography-mass spectrometry (GC-MS).
- Liquid chromatography-tandem mass spectrometry (LC-MS/MS).
- High-performance liquid chromatography (HPLC).
Test Preparation and Influencing Factors
- No fasting required.
- Statin medications inhibit upstream cholesterol synthesis, lowering levels.
- Sample stability good when frozen; avoid light exposure.
- Prematurity or low birth weight may affect reference ranges.
- Dietary cholesterol supplementation influences plasma levels.
Synonyms
- 7-DHC.
- Delta-7-dehydrocholesterol.