Cushing's Syndrome Although obese patients commonly have central obesity, hypertension, and glucose intolerance, they lack other specific stigmata of Cushing's syndrome (Chap. 336). Nonetheless, a potential diagnosis of Cushing's syndrome is often entertained. Cortisol production and urinary metabolites (17OH steroids) may be increased in simple obesity. Unlike in Cushing's syndrome, however, cortisol levels in blood and urine in the basal state and in response to corticotropinreleasing hormone (CRH) or ACTH are normal; the overnight 1-mg dexamethasone suppression test is normal in 90%, with the remainder being normal on a standard 2-day low-dose dexamethasone suppression test. Obesity may be associated with. | Chapter 074. Biology of Obesity Part 6 OTHER SPECIFIC SYNDROMES ASSOCIATED WITH OBESITY Cushing s Syndrome Although obese patients commonly have central obesity hypertension and glucose intolerance they lack other specific stigmata of Cushing s syndrome Chap. 336 . Nonetheless a potential diagnosis of Cushing s syndrome is often entertained. Cortisol production and urinary metabolites 17OH steroids may be increased in simple obesity. Unlike in Cushing s syndrome however cortisol levels in blood and urine in the basal state and in response to corticotropinreleasing hormone CRH or ACTH are normal the overnight 1-mg dexamethasone suppression test is normal in 90 with the remainder being normal on a standard 2-day low-dose dexamethasone suppression test. Obesity may be associated with excessive local reactivation of cortisol in fat by 110- hydroxysteroid dehydrogenase 1 an enzyme that converts inactive cortisone to cortisol. Hypothyroidism The possibility of hypothyroidism should be considered but it is an uncommon cause of obesity hypothyroidism is easily ruled out by measuring thyroid-stimulating hormone TSH . Much of the weight gain that occurs in hypothyroidism is due to myxedema Chap. 335 . Insulinoma Patients with insulinoma often gain weight as a result of overeating to avoid hypoglycemic symptoms Chap. 339 . The increased substrate plus high insulin levels promote energy storage in fat. This can be marked in some individuals but is modest in most. Craniopharyngioma and Other Disorders Involving the Hypothalamus Whether through tumors trauma or inflammation hypothalamic dysfunction of systems controlling satiety hunger and energy expenditure can cause varying degrees of obesity Chap. 333 . It is uncommon to identify a discrete anatomic basis for these disorders. Subtle hypothalamic dysfunction is probably a more common cause of obesity than can be documented using currently available imaging techniques. Growth hormone GH which exerts lipolytic activity is .
