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CASE FILES: BIOCHEMISTRY

A N SW E R S TO C A SE 50: C U SH IN G SY N D R O M E

Summary:

A 32-year-old female with irregular menses, hirsutism, mood

swings, weight gain, truncal obesity, hypertension, abdominal striae, ecchy-

moses, and elevated cortisol levels.

♦

Diagnosis: Cushing Syndrome

♦

Elevated ACTH level: Likely cause of adrenal hyperplasia from

ACTH-producing tumor

C L IN IC A L C O R R E L A T IO N

This patient presents with many of the classic findings of Cushing syndrome.

Adrenal hyperplasia can be caused by excessive stimulation from ACTH (pitu-

itary or ectopic production) or from a primary adrenal problem such as adenomas/

carcinomas. In addition to above symptoms, patients with Cushing syndrome are

also at risk for osteoporosis and diabetes mellitus (DM). The diagnosis is con-

firmed with elevated cortisol levels after a dexamethasone suppression test.

Treatment depends on the underlying etiology and is often surgical.

A PPR O A C H TO C U SH IN G SY N D R O M E

O bjectives

1.

Describe the biosynthesis of steroids in the adrenal gland.

2.

Explain from a biochemical standpoint why hypertension is a common

consequence of Cushing syndrome.

D efinitions

Abdominal striae: Stretch marks of the abdominal region.

ACTH (adrenocorticotropic hormone or corticotropin): Hormone pro-

duced in the anterior pituitary, which stimulates adrenal production of

cortisol.

Adenoma: Any benign tumor of glandular origin; typically found in the

adrenal, pituitary, and thyroid glands (note: once an adenoma has pro-

gressed to malignancy, it is referred to as an adenocarcinoma).

CRH (corticotropin-releasing hormone): Hormone produced in the

hypothalamus, which stimulates release of ACTH from the anterior

pituitary.

Cushing disease: A specific form of Cushing syndrome, which is caused

by an ACTH-secreting pituitary adenoma; represents approximately

66 percent of all cases of Cushing syndrome. Because of structural simi-

larities with melanocyte-stimulating hormone (MSH), excess ACTH from

pituitary adenomas can induce dermal hyperpigmentation.