ACTHDependent Hypercortisolism

Cushing's Disease

Overproduction of ACTH by a pituitary adenoma is responsible for 75 to 80% of endogenous hypercor-tisolism.

• Microadenomas are the most common cause of Cushing's disease. They are usually smaller than 10 mm, making them difficult to detect by pituitary imaging.13,46

• Macroadenomas, because of their size, may cause hypopituitarism, as well as visual field defect and headache.

Pituitary hyperplasia is very rare.

Diagnosis. Pituitary adenomas respond to CRH stimulation but are less responsive to gluco-corticoid suppression. Thus, pituitary adenomas tend to secrete high levels of ACTH in response to CRH stimulation but are incompletely suppressed by dexamethasone.26,27 About half of the pituitary adenomas in patients with Cushing's disease are found on conventional pituitary imaging studies. Those with negative pituitary imaging studies should undergo BIPSS with CRH stimulation. BIPSS is invasive, but it is the best test to differentiate Cushing's disease from occult ectopic ACTH-producing tumors. In addition, lateralization (gradient on the right or left side) can guide the surgeon to selectively explore and remove one side of the pituitary gland even when pituitary imaging studies are negative.13,40-42

Treatment. The standard treatment for patients with a pituitary adenoma is transsphenoidal hypophy-sectomy. Success rate varies between 70% and 98%, depending on the experience of the surgeon and the length of follow-up.47-51

Radiation therapy can cure 85% of children and is an option for initial treatment in pediatric patients.52,53 The risk of hypopituitarism after radiotherapy can be decreased dramatically by a focused stereo-taxic radiosurgery (gamma knife).53,54 Medical therapy with ketoconazole is not definitive but is often required in conjunction with radiotherapy to control hypercortisolism.17,55-57 Patients with microadenomas have a good prognosis, but their survival is still less than an age-matched control group, primarily because of cardiovascular diseases.58 Patients with macroadenomas die from both hypercortisolism and local tumor invasion.17

Clinical Signs

Symptoms and Metabolic Findings

Common symptoms:

• Proximal muscle weakness

• Psychological changes

• Amenorrhea

Less common symptoms:

• Backache, vertebral collapse, and fractures

Metabolic findings:

• Glucose intolerance

• Renal calculi

Figure 11-2. Signs and symptoms of Cushing's syndrome.

Common symptoms:

• Proximal muscle weakness

• Psychological changes

• Amenorrhea

Less common symptoms:

• Backache, vertebral collapse, and fractures

Metabolic findings:

• Glucose intolerance

• Renal calculi

Figure 11-2. Signs and symptoms of Cushing's syndrome.

Table 11

Was this article helpful?

0 0

Post a comment