Table 1.

Causes of CRF

Causes of CRF
Primary CRF	Alterations caused by cytokines, disturbance of hypothalamic regulatory circuits, changes in the central nervous system serotoninergic system, disturbance of circadian melatonin secretion, gene polymorphisms for regulatory proteins of oxidative phosphorylation
Secondary CRF	Sleep disturbance, infection, anemia, malnutrition, emotional distress, pain, reduced physical activity, alcohol/substance abuse, use of medications, comorbidities as COPD

Abbreviations: CRF, cancer-related fatigue; COPD, chronic obstructive pulmonary disease.