Fatigue, asthenia and daytime sleepiness are among the most common presenting symptoms in internal medicine. This article provides a structured overview of the main differential diagnoses such as hypothyroidism, diabetes mellitus, anemia, depression, heart failure, sleep apnea and adrenal insufficiency — including typical symptoms and diagnostics. Ideal for preparing for FSP, the medical licensing exam and M3.
Fatigue, Asthenia and Daytime Sleepiness
Main Complaints
Patients often report fatigue, asthenia or pronounced daytime sleepiness that affects both professional and private life.
Typical statements include:
- “I don’t feel like doing anything.”
- “I can barely get out of bed in the morning.”
- “Sometimes I even fall asleep in my office chair.”
The complaints usually develop insidiously and have noticeably worsened recently.
Possible Causes
- Endocrine / Metabolic
- Hypothyroidism (primary or secondary)
- Diabetes mellitus (hypo- or hyperglycemia)
- Hematologic
- Anemia
- Psychiatric
- Depression
- Cardiopulmonary
- Heart failure
- Sleep apnea syndrome
Differential Diagnoses
| Condition | Typical clues / Additional symptoms | Key diagnostics |
|---|---|---|
| Hypothyroidism (primary/secondary) | Cold intolerance, weight gain despite reduced appetite, dry skin, constipation Most common cause: Hashimoto’s thyroiditis |
TSH, fT3, fT4 |
| Diabetes mellitus | Polyuria, polydipsia, polyphagia, dizziness, sweating, mycotic infections, urinary tract infections | Blood glucose, HbA1c |
| Anemia | Pallor, exertional dyspnea, tachycardia, exercise intolerance | Blood count, ferritin |
| Depression | Loss of interest, lack of drive, sleep disturbances, negative thoughts, self-harm | History, exclusion of organic causes |
| Heart failure | Exertional dyspnea, edema, orthopnea, nocturia, palpitations; Risk factors: age, obesity, smoking, hypertension, diabetes mellitus, hypercholesterolemia | ECG, echocardiography, BNP |
| Sleep apnea syndrome | Snoring, breathing pauses | Polysomnography (sleep laboratory) |
Differential Diagnoses
-
Adrenal insufficiency (Addison’s disease)
- Muscle weakness
- Weight loss
- Hypotension
- Dizziness
- Hyperpigmentation
- Salt craving
- Gastrointestinal complaints
-
Burnout syndrome
- Emotional exhaustion
- Reduced performance
- Feeling overwhelmed
