CASE FILES: BIOCHEMISTRY
[50.2] The hirsutism observed in the patient above is best explained by which
of the following?
A. ACTH stimulating synthesis of adrenal androgens
B. CRH stimulating synthesis of adrenal androgens
C. Cortisol activating aldosterone receptors
D. Cortisol stimulating expression of adrenal androgen biosynthetic
[50.3] The characteristic accumulation of adipose tissue in the facial, truncal,
and cervical regions of the body in patients with Cushing syndrome is
best explained by which of the following?
A. Excess adrenal androgens due to adrenal tumor
B. Excess cortisol over long periods of time
C. Cross stimulation of mineralocorticoid receptors by cortisol
D. Increased production of MSH
E. Increased proteolysis
[50.4] The most common cause of hypercortisolism is which of the following?
A. Adrenal tumor that secretes excess cortisol and mineralocorticoid
B. Lung tumor that secretes excess ACTH that leads to excess cortisol
in the blood.
C. Administration of synthetic cortisol by physician
D. Pituitary adenoma that secretes excess ACTH, leading to excess
cortisol in the blood.
A nsw ers
A. The body’s humoral stress pathway can no longer regulate cortisol
levels via a negative feedback loop. By administering a synthetic
form of cortisol (dexamethasone), the physician is testing the body’s
natural ability to reduce cortisol production. However, a patient with
Cushing syndrome produces excess cortisol from one of several
major sources, such as an ACTH-secreting pituitary adenoma, an
ACTH-secreting lung tumor, or a cortisol-secreting adrenal tumor.
Either one of these sources will be unaffected by the dexamethasone
suppression test, thus exhibiting no change in blood cortisol levels.
If the stress humoral pathway is intact, the test will show a drop in
A. Androgenic phenotypes are commonly seen in Cushing syndrome
because ACTH, frequently in excess, stimulates synthesis of adrenal
androgens in addition to cortisol.