Chronic fatigue is a pervasive feeling of enduring, profound tiredness that persists despite adequate rest and sleep. Anyone who has had the flu has experienced the distinct difference between everyday tiredness and fatigue. Chronic fatigue is a symptom of many diverse illnesses, arising from different organ systems. Determining the cause of chronic fatigue often proves challenging because of the many diseases and disorders that can cause this symptom.
Anemia
Anemia describes a medical condition in which the number of red blood cells is abnormally decreased, limiting the oxygen-carry capacity of your blood. The most frequent symptom associated with anemia is fatigue, reports the National Heart, Lung and Blood Institute. Many inherited and acquired conditions can cause anemia, including iron or vitamin B12 deficiency, sickle cell anemia, thalassemia, hemolytic anemia and anemia of chronic disease. Treatment for anemia depends on the underlying cause.
Cancer
Cancer is often present for many years before organ-specific symptoms develop. Generalized symptoms, however, are common to nearly all cancers. One of the hallmark, generalized symptoms of cancer is chronic fatigue, reports the American Cancer Society. Other generalized symptoms include unexplained fever and unintentional weight loss. The Centers for Disease Control and Prevention reports that cancer remains the second most frequent cause of death in the United States. More than 1,529,000 adults and children in the United States are expected to be diagnosed with cancer in 2010, according to the American Cancer Society.
COPD
Chronic obstructive pulmonary disease, or COPD, is a degenerative lung condition in which inflammation and damage to the airways causes decreased lung function. National Jewish Health reports that increasing fatigue is an early warning sign of COPD. Fatigue associated with COPD reflects a persistent state of oxygen deprivation and the increased work of breathing necessitated by the decreased functional capacity of the lungs. Cigarette smoking causes the vast majority of COPD among Americans. Persistent exposure to the chemicals in cigarette smoke overwhelms the lungs' capacity to heal themselves and irreversible damage occurs. The National Heart, Lung and Blood Institute reports that approximately 12 million cases of COPD have been diagnosed among Americans, and an equal number may be living with the disease who have not yet been diagnosed.
Hypothyroidism
A deficiency in the production of thyroid hormones causes hypothyroidism, also known as underactive thyroid disease. Your thyroid dictates the overall rate of metabolism in your body. In the absence of adequate amounts of the thyroid hormones, the metabolic rate decreases throughout your body. A cardinal symptom of hypothyroidism is chronic fatigue, notes the New York Thyroid Center of Columbia University Medical Center. Other accompanying symptoms include weight gain, cold intolerance, depression, constipation and irregular menstruation in women. The American Association of Clinical Endocrinologists states underactive thyroid disease affects roughly 25 million Americans.
Chronic Fatigue Syndrome
Chronic fatigue syndrome is a cluster of symptoms, including: chronic fatigue, lasting six months or longer; muscle and joint pain; sore throat; headaches; tender lymph nodes in the armpit or neck; and sleep that fails to provide refreshment. Chronic fatigue syndrome is diagnosed only if all other medical and psychiatric causes of the presenting cluster of symptoms have been ruled out. According to the Centers for Disease Control and Prevention, the cause of chronic fatigue syndrome has yet to be identified.
