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ACTH = adrenocorticotropic hormone.

'Many clinical vignette questions include the plasma levels of various hormones or the results of a dexametha-sone test. Knowing which hormone levels are increased, decreased, normal, or not applicable in certain clinical conditions will be of great assistance in answering these questions.

'The dexamethasone suppression test is based on the ability of dexamethasone (a synthetic glucocorticoid) to inhibit the secretion of ACTH and Cortisol. If the adenohypophysis-adrenal cortex axis is normal, dexamethasone inhibits ACTH and Cortisol secretion by negative feedback.

c. Treatment is with surgery or spironolactone, which is an aldosterone receptor antagonist and, therefore, an effective antihypertensive and diuretic agent.

2. Cushing syndrome a. Cause. Elevated levels of Cortisol (hypercortisolism) commonly are caused by an ACTH-secreting adenoma within the adenohypophysis (seen in 70% of cases; known as Cushing disease), an adrenal adenoma (25% of cases), or adrenal hyperplasia (5% of cases). Oat cell carcinoma of the lung also may produce ACTH ectopically. However, Cushing syndrome most commonly is caused iatro-genically by corticosteroid drug therapy.

b. Clinical findings include: mild hypertension, osteoporosis with back pain, central obesity, moon facies, purple skin striae, and impaired glucose tolerance.

c. Treatment is with ketoconazole, an inhibitor of steroid biosynthesis.

3. Congenital adrenal hyperplasia (CAH)

a. Cause. CAH most commonly is caused by mutations in the genes for enzymes involved in adrenocortical steroid biosynthesis (e.g., 21-hydroxylase deficiency, 11 (J-hydroxylase deficiency). In 21-hydroxylase deficiency (seen in 90% of cases), virtually no synthesis of aldosterone or Cortisol occurs. As a result, inter mediates are funneled into androgen biosynthesis, and androgen levels are elevated as a result.

b. Clinical findings. The elevated levels of androgens lead to virilization of a female fetus that can range from mild clitoral enlargement to complete labioscro-tal fusion with a phalloid organ. Increased urinary levels of 17-ketosteroids are found. Because Cortisol cannot be synthesized, negative feedback to the adenohy-pophysis does not occur, and ACTH continues to stimulate the adrenal cortex, resulting in adrenal hyperplasia.

c. Treatment. Depending on the severity of the condition, treatment may include surgical reconstruction and steroid replacement.

4. Primary adrenal insufficiency (Addison disease)

a. Cause. Primary adrenal insufficiency commonly is caused by autoimmune destruction of the adrenal cortex. Other causes include adrenal tuberculosis, fungal infection, and adrenal hemorrhage.

b. Clinical findings include: fatigue, anorexia, nausea, weight loss, hypoglycemia, hypotension, and hyperpigmentation of the skin as a result of increased secretion of melanocyte-stimulating hormone.

c. Treatment is steroid replacement therapy.

5. Secondary adrenal insufficiency a. Cause. Secondary adrenal insufficiency is caused by a disorder of the hypothalamus or adenohypophysis that decreases ACTH secretion. The most common cause is iatrogenic suppression of ACTH as a side effect of corticosteroid drug therapy.

b. Clinical findings are very similar to those of Addison disease, except that there is no hyperpigmentation of the skin.

c. Treatment is steroid replacement therapy.

Hi. ADRENAL MEDULLA

A. General features. The adrenal medulla contains chromaffin cells, which are modified postganglionic sympathetic neurons that are derived embryologically from neural crest cells. Preganglionic sympathetic axons (through splanchnic nerves) synapse on chromaffin cells, causing these cells to secrete catecholamines (90% epinephrine and 10% norepinephrine).

B. Clinical considerations

1. Pheochromocytoma is a relatively rare neoplasm (usually not malignant) of neural crest origin that contains both epinephrine and norepinephrine.

a. Characteristics. Pheochromocytoma occurs within families, primarily in adults, as part of the multiple endocrine neoplasia (MEN) type Ila syndrome (pheochromocytoma, hyperparathyroidism, and medullary carcinoma of the thyroid) or in association with von Recklinghausen neurofibromatosis. It usually is found in the region of the adrenal gland, but also is found in extra-adrenal sites (e.g., near the aortic bifurcation called the organ of Zuckerkandl).

b. Clinical findings. It is associated with persistent or paroxysmal hypertension, anxiety, tremor, profuse sweating, pallor, and chest and abdominal pain.

c. Diagnosis. Increased urinary levels of vanillylmandelic acid metanephrine, inability to suppress catecholamines with clonidine, and hyperglycemia are common laboratory findings.

d. Treatment consists of surgery or phenoxybenzamine (an a-adrenergic antagonist).

A large mass (arrc the kidney (K).The ally occurs unilatei with Cushing sym enlarged, but they glands, except for hyperplasia, the ac man PJ, Glazer HS raphy. New York, R

A large mass (arrc the kidney (K).The ally occurs unilatei with Cushing sym enlarged, but they glands, except for hyperplasia, the ac man PJ, Glazer HS raphy. New York, R

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IV. RADIOLOC/

A. Computed adrenal ad

Enlarged Kidney Scan

Figure 13-1. (A) CT scan of a patient with Cashing syndrome caused by an adrenal adenoma. A large mass (arrows) is seen in the left adrenal gland, posterior to the pancreas and anterior to the kidney (K). The normal right adrenal gland is shown (arrowhead). An adrenal adenoma usually occurs unilaterally, whereas adrenal hyperplasia occurs bilaterally. (B) CT scan of a patient with Cushing syndrome caused by adrenal hyperplasia. Both adrenal glands (arrows) are enlarged, but they retain their normal anatomic shapes. The normal appearance of the adrenal glands, except for the increased size, may confound the diagnosis. In some cases of adrenal hyperplasia, the adrenal glands show bilateral nodularity. [Reprinted with permission from Wey-man PJ, Glazer HS: Adrenals. In Lee JKT, Sagel SS, Stanley RS (eds): Computed Body Tomography New York, Raven Press, 1983.]

Figure 13-1. (A) CT scan of a patient with Cashing syndrome caused by an adrenal adenoma. A large mass (arrows) is seen in the left adrenal gland, posterior to the pancreas and anterior to the kidney (K). The normal right adrenal gland is shown (arrowhead). An adrenal adenoma usually occurs unilaterally, whereas adrenal hyperplasia occurs bilaterally. (B) CT scan of a patient with Cushing syndrome caused by adrenal hyperplasia. Both adrenal glands (arrows) are enlarged, but they retain their normal anatomic shapes. The normal appearance of the adrenal glands, except for the increased size, may confound the diagnosis. In some cases of adrenal hyperplasia, the adrenal glands show bilateral nodularity. [Reprinted with permission from Wey-man PJ, Glazer HS: Adrenals. In Lee JKT, Sagel SS, Stanley RS (eds): Computed Body Tomography New York, Raven Press, 1983.]

2. Neuroblastoma is an extracranial neoplasm that contains primitive neuroblasts of neural crest origin.

a. Characteristics. Neuroblastoma is the most common solid tumor in children and may metastasize to the bone marrow, liver, and orbit. It is found in extra-adrenal sites, usually along the sympathetic chain ganglia (60%) or within the adrenal medulla (40%).

b. Clinical findings. Neuroblastoma is associated with opsoclonus, which is characterized by rapid, irregular, horizontal and vertical movements of the eye ("dancing eyes").

c. Diagnosis. A neuroblastoma contains small cells arranged in Homer-Wright pseudorosettes. Increased urinary levels of vanillylmandelic acid and metanephrine are found.

d. Treatment includes surgical excision, radiation, and chemotherapy.

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