Hypermetabolism is a condition characterized by an abnormal increase in the body’s basal metabolic rate. It usually occurs when there is significant injury or multiple traumas to the body, such as surgery, long bone fractures, or infections. Sepsis, burns, steroid therapy and bone marrow transplants also cause it. Hypermetabolism is one of the major symptoms of hyperthyroidism, or overactive thyroid.
This condition causes increased peripheral insulin resistance; elevated catabolism of protein, carbohydrates, and triglycerides; and a negative nitrogen balance in the body. Symptoms include sudden weight loss, anemia, and fatigue. Individuals suffering from hyperthyroidism may experience other symptoms, such as rapid heart rate, irregular heartbeat, and insomnia, along with a shortness of breath, muscle weakness, and nervousness. Individuals may also experience increased sensitivity to heat or excessive sweating due to elevated body heat.
While hyperthyroidism is a common form of hypermetabolism, the condition is not always a result of a thyroid disorder. Many illnesses can cause an increase in metabolism as the body attempts to fight the illness and heal itself. This increased hypermetabolic state is referred to as extrathyroidal, meaning it is not associated with the thyroid. This type is normally seen in cancer patients or patients with severe body trauma.
A positron emission tomography (PET) scan is performed to identify areas of hypermetabolic activity within the body and to determine the cause. A PET scan involves injection of a radioactive substance into a patient’s vein. The patient then waits one hour to allow the substance to absorb throughout the body, then lies on a table that is slid into a tunnel-shaped hole in the center of the PET scanner.
Some recovering anorexics or bulimics may experience this condition in the early stages of their recovery. The prolonged starvation periods associated with these eating disorders result in a significant decrease in the body's metabolic rate as the body goes into starvation mode. Once the recovering patient resumes a normal diet, their body's metabolic rate rapidly accelerates before stabilizing to normal.
Since hypermetabolism is a symptom and not a disease, treating it requires addressing the underlying illness. The duration depends on the severity of the illness or the degree of the trauma to the body. In most cases, once the underlying cause is remedied, so is the metabolic problem. Although the condition is a signal of a potentially more serious issue, it is one of the body's many defense mechanisms against disease and injury.