CLINICAL CASES
439
cases, also results in decreased production of aldosterone, the other principal
steroid hormone produced by this gland. If aldosterone levels are insufficient,
characteristic electrolyte abnormalities are evident owing to increased excre-
tion of Na+ and decreased excretion of K+ chiefly in urine but also in sweat,
saliva, and the GI tract. This condition leads to isotonic urine and decreased
blood levels of Na+ and Cl- with increased levels of K+. Left untreated,
aldosterone insufficiency produces severe dehydration, plasma hyper-
tonicity, acidosis, decreased circulatory volume, hypotension, and circula-
tory collapse.
Cortisol deficiency impacts carbohydrate, fat, and protein metabolism and
produces severe insulin sensitivity. Gluconeogenesis and liver glycogen for-
mation are impaired, and hypoglycemia results. As a consequence, hypoten-
sion, muscle weakness, fatigue, vulnerability to infection, and stress are early
symptoms. A characteristic hyperpigmentation on both exposed and unex-
posed parts of the body is evident. Decreased blood levels of cortisol in
Addison disease lead to increased blood levels of both ACTH and P-
lipotropin reflecting decreased feedback inhibition by cortisol of their synthe-
sis. P-Lipotropin has melanocyte-stimulating activity accounting for the
increased pigmentation. The disease is progressive, with the risk of a poten-
tially fatal adrenal crisis triggered by infection or other trauma.
Secondary adrenal insufficiency may result from lesions in the hypothala-
mus or pituitary, leading to impaired release of ACTH. This condition does not
exhibit hyperpigmentation because release of feedback inhibition of ACTH
production by low cortisol levels cannot overcome the primary defect in
ACTH production. Usually, aldosterone secretion is normal.
By contrast, Cushing syndrome results from cortisol overproduction and
most commonly is caused by a tumor in either the adrenal gland or pituitary.
C O M P R E H E N SIO N Q U E ST IO N S
[49.1] A 29-year-old female patient exhibited a rounded face, hirsutism,
upper body obesity, easily bruised skin, severe fatigue, muscle weak-
ness, and anxiety. She also complained of irregular periods. A long-
term asthma sufferer, she had been prescribed prednisone for the past
2 years. Findings on examination revealed high fasting blood glucose
levels and high blood pressure. Cortisol levels were below normal.
Which one of the following is the most likely explanation to account
for the patient’s symptoms?
A. Decreased levels of insulin
B. Increased levels of testosterone
C. Decreased secretion of ACTH
D. Excess exogenous glucocorticoid hormone
E. Increased hepatic metabolism of steroid hormones
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