Hypermetabolism is defined as an elevated resting energy expenditure (REE) > 110% of predicted REE.
Outward symptoms of hypermetabolism may include:
- Weight loss
- Anemia
- Fatigue
- Elevated heart rate
- Irregular heartbeat
- Insomnia
- Dysautonomia
- Shortness of breath
- Muscle weakness
- Excessive sweating
Pathophysiology
During the acute phase, the liver redirects protein synthesis, causing up-regulation of certain proteins and down-regulation of others. Measuring the serum level of proteins that are up- and down-regulated during the acute phase can reveal extremely important information about the patient's nutritional state. The most important up-regulated protein is C-reactive protein, which can rapidly increase 20- to 1,000-fold during the acute phase.
Hypermetabolism also causes expedited catabolism of carbohydrates, proteins, and triglycerides in order to meet the increased metabolic demands.
Diagnosis
Quantitation by indirect calorimetry, as opposed to the Harris-Benedict equation, is needed to accurately measure REE in cancer patients.
- Fatal familial insomnia: Manifestation: Hypermetabolism in the thalamus occurs and disrupts sleep spindle formation that occurs there.
- Graves' disease: Manifestation: Excess hypermetabolically-induced thyroid hormone activates sympathetic pathways, causing the eyelids to retract and remain constantly elevated.
- Anorexia and bulimia: Manifestation: The prolonged stress put on the body as a result of these eating disorders forces the body into starvation mode. Some patients recovering from these disorders experience hypermetabolism until they resume normal diets.
- Astrocytoma: Manifestation: Causes hypermetabolic lesions in the brain
Treatment
Ibuprofen, polyunsaturated fatty acids, and beta-blockers have been reported in some preliminary studies to decrease REE, which may allow patients to meet their caloric needs and gain weight.