Cushing's syndrome is a hormonal disease caused by the overproduction of certain adrenal hormones, particularly cortisol. In a normal person, the body releases cortisol in measured amounts each day, but in Cushing's patients cortisol is produced almost continuously. Cushing's disease is Cushing's syndrome caused by a tumor on the pituitary gland that causes an excess of ACTH which directly increases cortisol production, and was the cause of Cushing's syndrome in the episode Heavy.
Cushing's patients gain weight rapidly no matter what their diet or exercise regimes. However, unlike obese patients, the fat tends to accumulate around the face (giving it a moon-like appearance that is characteristic of the disease) and the torso, leaving the arms and legs roughly their normal size. It can also cause a buildup of fat on the back, leading to the appearance of a "buffalo hump".
The most common cause of Cushing's syndrome is a side effect of drugs that treat other conditions. Although stopping the drugs will stop the Cushing's, the difficulty in dealing with the underlying illness still remains. More rarely, the syndrome is caused by the overproduction of hormones by the body itself.
Treatment for Cushing's where the body produces cortisol in excess is difficult. Patients require cortisol (or else Addison's disease results) so the adrenal gland that produces the hormone can't be removed. However, the cause of internal overproduction of the hormone can usually be traced to a cortisol producing tumor on an adrenal gland or an ACTH producing tumor on the pituitary gland. In such cases, surgery can be effective although the risk to the patient is great. Otherwise, drugs that inhibit the production and metabolism of cortisol are the only treatment.
Cushing's patients often face tremendous prejudice from medical professionals who write off their "symptoms" as the result of overeating. However, a test of cortisol in the blood usually indicates elevated levels of the hormone in Cushing's patients, while in obese patients these levels are normal. However, there is a handy mnemonic to describe the symptoms.
C - Central obesity, Cervical fat pads, Collagen fibre weakness, Comedones (acne) U - Urinary free cortisol and glucose increase S - Striae, Suppressed immunity H - Hypercortisolism, Hypertension, Hyperglycaemia, Hirsutism I - Iatrogenic (Increased administration of corticosteroids) N - Noniatrogenic (Neoplasms) G - Glucose intolerance, Growth retardation (Source:Wikipedia)
In the first-season episode "Heavy", the 10-year-old patient Jessica Simms is brought to House after suffering a heart attack on the playground at school. Her weight causes conflict among the staff as they argue about how much it did or didn't contribute to the problem.