was bedeutet low cortisol — what does this mean exactly?

Low cortisol means the adrenal cortex is not producing enough cortisol, a key stress hormone. This can result from primary adrenal insufficiency (Addison's disease), secondary insufficiency (pituitary or hypothalamic dysfunction), or relative adrenal insufficiency. Symptoms include fatigue, weight loss, low blood pressure, nausea, and hyperpigmentation. Crucially, consumer DNA tests (e.g., MyBody-X) do not measure current cortisol levels; they assess genetic variants that may influence cortisol metabolism or stress response, but effect sizes are small and not diagnostic. A clinical low cortisol diagnosis requires blood, saliva, or 24-hour urine tests. Evidence for genetic associations is mostly GWAS or mechanistic, not strong enough for clinical decisions. Do not start hormone therapy without medical supervision. Be aware that some companies overstate the relevance of single SNPs for hormone levels.