790
U N I T 9
Endocrine System
Other tests include measurement of the plasma lev-
els of ACTH.
39,40,47,48
Adrenocorticotropic hormone lev-
els should be normal or elevated in ACTH-dependent
Cushing syndrome (Cushing disease and ectopic ACTH),
and low in non–ACTH-dependent Cushing syndrome
(adrenal tumors). Various suppression or stimulation
tests of the HPA system are performed to delineate the
cause further. MRI or CT scans afford a means for locat-
ing adrenal or pituitary tumors.
Untreated, Cushing syndrome produces serious mor-
bidity and even death. The choice of surgery, irradiation,
or pharmacologic treatment is determined largely by the
cause of the hypercortisolism. The goal of treatment for
Cushing syndrome is to remove or correct the source of
hypercortisolism without causing permanent pituitary or
adrenal damage.
40,48
Transsphenoidal removal of a pitu-
itary adenoma or a hemihypophysectomy is the preferred
method of treatment for Cushing disease. This allows
removal of only the tumor rather than the entire pituitary
gland. After successful removal, the person must receive
cortisol replacement therapy for 6 to 12 months or until
adrenal function returns. Pituitary radiation therapy may
also be used, but the full effects of treatment may not be
realized for 3 to 12 months. Unilateral or bilateral adre-
nalectomy may be done in the case of adrenal adenoma.
When possible, ectopic ACTH-producing tumors are
removed. Pharmacologic agents that block steroid syn-
thesis (i.e., mitotane, ketoconazole, and metyrapone)
may be used to treat persons with ectopic tumors or adre-
nal carcinomas that cannot be resected.
39,40
Many of these
patients also require
Pneumocystis jiroveci
(formerly
known as
Pneumocystis carinii
) pneumonia prophylaxis
because of the profound immunosuppression caused by
the excessive glucocorticoid levels.
Incidental Adrenal Mass
An incidentaloma is a mass lesion found unexpectedly
in an adrenal gland by an imaging procedure (done for
other reasons), most commonly CT (but also MRI and
ultrasonography).
49
It has been increasingly recognized
since the early 1980s.
50
The prevalence of adrenal inci-
dentalomas at autopsy is approximately 10 to 100 per
1000. In CT series, 0.6% to 4.4% are the usual figures
published. Incidentalomas also can occur in other organs
(e.g., pituitary, thyroid). The two most important ques-
tions are (1) is the mass malignant, and (2) is the mass
hormonally active (i.e., is it functioning)?
Primary adrenal carcinoma is quite rare, but other
cancers, particularly lung cancers, commonly metasta-
size to the adrenal gland (other cancers include breast,
stomach, pancreas, colon, kidney, melanomas, and
lymphomas). The size and imaging characteristics of
the mass may help determine whether the tumor is
benign or malignant. The risk of cancer is high in adre-
nal masses larger than 6 cm. Many experts recommend
surgical removal of masses larger than 4 cm, particu-
larly in younger patients.
49,50
Appropriate screening to
exclude a hormonally active lesion includes tests to rule
out pheochromocytoma, Cushing syndrome, and Conn
syndrome (mineralocorticoid excess).
SUMMARY CONCEPTS
■■
The adrenal cortex produces three types of
hormones: mineralocorticoids, glucocorticoids,
and adrenal androgens.The mineralocorticoids,
along with the renin–angiotensin mechanism,
aid in controlling body levels of sodium and
potassium.The glucocorticoids have anti-
inflammatory actions and aid in regulating
glucose, protein, and fat metabolism during
periods of stress.The adrenal androgens exert
little effect on daily control of body function, but
they probably contribute to the development of
body hair in women. Disorders of the adrenal
cortex include those that produce adrenocortical
hormone insufficiency or excess.
■■
Congenital adrenal hyperplasia describes a
genetic defect in the cortisol pathway resulting
from a deficiency of one of the enzymes needed
for its synthesis. Depending on the enzyme
involved, the disorder causes virilization of
female infants and, in some instances, fluid and
electrolyte disturbances because of impaired
mineralocorticoid synthesis.
■■
Primary adrenal cortical insufficiency, which
can be caused by destruction of the adrenal
gland (Addison disease) or by dysfunction of
the HPA system, is manifested by signs of a
mineralocorticoid deficiency (impaired ability
to regulate salt and water elimination) and a
glucocorticoid deficiency (impaired ability to
regulate blood glucose and control the effects
of the immune and inflammatory responses).
Adrenal insufficiency requires replacement
therapy with adrenal cortical hormones. Acute
adrenal insufficiency is a life-threatening situation.
■■
Adrenal corticosteroid excess, or Cushing
syndrome, results in derangements in glucose
metabolism, disorders of sodium and potassium
regulation (increased sodium retention and
potassium loss), impaired ability to respond to
stress because of inhibition of inflammatory
and immune responses, and signs of increased
androgen levels such as hirsutism.This syndrome
may result from pharmacologic doses of
glucocorticoids, a pituitary or adrenal tumor, or
an ectopic tumor that produces ACTH.
■■
An incidentaloma is a mass lesion found
unexpectedly in an adrenal gland (and other
glands) by an imaging procedure done for other
reasons. Incidentalomas are being recognized
with increasing frequency, emphasizing the need
for correct diagnosis and treatment.
