Loss of muscle mass
The loss of muscle tissue means the loss of cells that produce energy. More than half of people with severe RA, according to one study, are affected by a condition called cachexia, in which muscle mass decreases and fatigue increases. Cachexia is linked with overactive immune system cytokines; in fact, tumor necrosis factor-alpha – the cytokine targeted by the biologic medications adalimumab (Humira), etanercept (Enbrel) and infliximab (Remicade) – is sometimes called ‘cachectin’ because of its connection with cachexia.
Looking deeper
What happens when major issues have been sorted through but the source of fatigue cannot be pinpointed? Doctors may order a series of lab tests that can provide clues or uncover an as-yet-undiagnosed condition.
White blood cell (WBC) count. A high level of WBCs, which are the immune system cells that fight bacteria and viruses, usually indicates an underlying infection that may be causing the body to use extra energy in attempts to fight off bacteria or a virus.
The Chem-20 panel. This standard blood test of 20 chemicals measures electrolytes like calcium, potassium and sodium, which help cells produce energy. Abnormal levels of the proteins, enzymes or chemicals, including glucose or carbon dioxide, may indicate problems with metabolism, the liver or kidneys, or it may indicate other chronic conditions, like hypoglycemia, which may reduce energy levels.
Thyroid-stimulating hormone (TSH) test. A TSH level that is too high indicates the pituitary gland is working overtime in an attempt to get the thyroid to pump out enough of the hormones that keep metabolism and energy production at a normal level. If the thyroid gland is not producing enough, the condition is called hypothyroidism. Fatigue is a major symptom of hypothyroidism, sometimes an autoimmune disease in its own right, which occurs at a higher frequency among people with autoimmune diseases like RA.
Urinalysis. Urine can be tested to see if bacteria, excess protein or blood is present. Abnormal results may indicate the presence of a urinary tract infection, kidney problems or metabolic disorders such as anemia or diabetes.
Pulse oximetry test. This simple test measures oxygen levels in the blood. Blood that is not well saturated with oxygen can be a reason for fatigue. Oxygen levels may be lower than normal in people with lung problems or obstructive sleep apnea.
Sleep study. This overnight test looks for sleep problems that might affect the amount of restorative sleep a person gets, such as obstructive sleep apnea.
