Abnormal basal metabolic rate

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Abnormal basal metabolic rate
ICD-10 R94.8
ICD-9 794.7

Abnormal basal metabolic rate refers to a high or low basal metabolic rate (BMR). It has numerous causes, both physiological (part of the body's normal function) and pathological (associated with disease).

Causes[edit]

Physiological[edit]

An abnormal basal metabolic rate is not necessarily indicative of disease; a number of physiological factors can alter the BMR by influencing cellular metabolic activity.[1] For instance, males are more likely than females to have a high BMR, and in women, the BMR may rise to abnormal levels during pregnancy or lactation.[2] An individual's BMR varies greatly with age: infants and children typically have a high BMR, required for growth, while the elderly have a low BMR.[1] Tall, thin people have a higher BMR than their shorter counterparts, even with the same weight, due to the greater surface area of their skin.[3] The metabolic rate also decreases during sleep and increases in exercise, and individuals who exercise regularly have a higher BMR than those who are sedentary.[1] Environmental temperature also has an effect: the BMR is increased in both heat and cold.[3]

Pathological[edit]

A common pathological cause for a high BMR is fever, since a rise in body temperature increases the rate of cellular metabolic reactions.[1] It is estimated that for every degree Fahrenheit of rise in body temperature, the BMR increases by 7 per cent.[3]

Thyroid disease also has a marked effect on BMR, since thyroid hormones regulate the rate of cellular metabolism.[3] Hyperthyroidism—in which there is an increase in the production of thyroid hormones—leads to a high BMR, while hypothyroidism—in which thyroid hormones are depleted—causes a low BMR.[1]

Prolonged periods of abnormal nutrition cause an adaptive change in BMR; this helps the body to maintain a stable body weight in response to the change in food supply. In prolonged malnutrition, the BMR declines, while in prolonged overnutrition, the BMR is increased.[1] Cancer sometimes causes an increase in BMR, perhaps because the cancer cells that form tumors have a high level of metabolic activity.[1]

References[edit]

  1. ^ a b c d e f g Bijlani, R. L.; Manjunatha, S. (2010). Understanding Medical Physiology (4th ed.). Jaypee Brothers. p. 383. ISBN 9789380704814. 
  2. ^ Lieberman, Michael; Marks, Allan D. (2009). Marks' Basic Medical Biochemistry: A Clinical Approach. Lippincott Williams & Wilkins. ISBN 9780781770224. 
  3. ^ a b c d DeBruyne, Linda; Whitney, Eleanor; Pinna, Kathryn (2007). Nutrition and Diet Therapy. Cengage Learning. p. 150. ISBN 9780495119166.