Myths vs facts: Cortisol and Müdigkeit

Cortisol is often called the 'stress hormone,' but the reality is more nuanced. Myth: High cortisol directly causes fatigue. Fact: Cortisol follows a diurnal rhythm – high in the morning, low at night. Chronic stress can disrupt this rhythm, leading to elevated evening levels that impair sleep quality and contribute to fatigue. However, fatigue is multifactorial (sleep deprivation, iron deficiency, thyroid issues, psychological factors). A single cortisol measurement from a home test (e.g., MyBody-X Hormon & VitalCheck) is insufficient to diagnose a disorder. Evidence for genetic tests (e.g., COMT 'warrior/worrier') is weak: large GWAS (Border 2019, n=620k) show only tiny, clinically non-actionable effects. Bottom line: Home cortisol tests may offer clues but cannot replace medical diagnosis. Persistent fatigue requires clinical evaluation with multiple measurements (saliva, serum) and history.