Campbell Adrenal Disorders 2021 Flashcards
Cells of this tissue zone are the sole source of aldosterone
Zona glomerulosa
** Aldosterone regulates electrolyte metabolism by stimulating epithelial cells of the distal nephron to reabsorb Na+ and Cl−, while secreting H+ and K+.
Site of glucocorticoid production.
Expression of enzymes: 17alpha-hydroxylase, 21-hydroxylase, and 11beta-hydroxylase.
Zona fasciculata
** Cortisol: primary glucocorticoid in humans, controlled by ACTH
Production of DHEA, sulfated DHEAS, and androstenedione
Zona reticularis
Lies at the center of the adrenal;
Integral part of the autonomic nervous system;
Secretes catecholamines;
Source of metanephrine and normetanephrine
Adrenal medulla
Catalyzes conversion of NE to epineprhine
Expressed in the adrenal medulla, brain, and organ of Zuckerkandl
Phenyethanolamine-N-methyltransferase (PNMT)
Hypercortisolism secondary to excessive production of glucocorticoids by the adrenal cortex.
Cushing syndrome
Three main groups of causes of Cushing syndrome
Exogenous: iatrogenic glucocorticoid administration
ACTH dependent: elevated serum corticotropin level by pathology extrinsic to adrenal (85% of Cushing syndrome)
ACTH independent: unregulated overproduction of glucocorticoids by the adrenal (rare)
Most common cause of hypercortisolism in the West.
Exogenous Cushing syndrome
85% of endogenous Cushing syndrome
Majority: primary pituitary pathology
Other causes: Ectopic ACTH production, ectopic CRH production
ACTH dependent Cushing Syndrome
Cushing Syndrome vs. Cushing Disease vs. Cushing Triad
Syndrome: Hypercortisolism secondary to excessive production of glucocorticoids
Disease: hypercortisolism through excessive secretion of ACTH by the pituitary gland/macroadenoma
Triad: triad of elevated intracranial pressure (widened pulse pressure, irregular respiration, bradycardia)
ACTH-producing nonpituitary tumors
Almost always malignant
10% of Cushing syndrome
Ectopic ACTH Syndrome
Extremely reare
<1% of Cushing syndrome
Bronchial carcinoma most common culprit
Ectopic CRH
Uncontrolled hypersecretion of cortisol by adrenal tissues
ACTH-independent Cushing syndrome
** Adrenal neoplasms and bilateral adrenal disease are in this group
Multiple large (4cm) nodules replacing the glands
Each gland weighs > 60 g
<1% of Cushing syndrome
ACTH-independent Macronodular Adrenal Hyperplasia (AIMAH)
Normal-sized adrenals
Black or brown cortical nodules
<1% of Cushing syndrome
Autosomal Carney complex (50%): spotty skin and mucous membrane lesions
Primary pigmented nodular adrenocortical disease (PPNAD)
Cushing syndrome
Central obesity Moon facies Buffalo hump Proximal muscle weakness Easy bruisability Abdominal striae
Metabolic syndrome (dyslipidemia, insulin resistance, hypertension
**These are non-specific
___% of patients with Cushing syndrome exhibit ___.
50%
Urolithiasis
** Stone formers with cushingoid features also should receive a hypercortisolemia evaluation
Hypercortisolemia inbsence of an overt cushingoid phenotype.
Autonomous Cortisol Secretion (subclinical Cushing syndrome)
Explain:
Low-dose dexamethasone suppression test
Low-dose dexamethasone should act on corticotropic cells of ant. pituitary gland –> suppresses ACTH production –> decreases serum cortisol
Failure to suppress cortisol levels: Cushing syndrome
DOES NOT delineate cause of hypercortisolism and cannot reliably detect subclinical Cushing syndrome
Explain:
Late night salivary cortisol
Midnight plasma cortisol
Cushing syndrome causes disruption of diurnal variation of cortisol levels
Normal: Cortisol peaks in the AM, decreases in the PM
Cushing: Persistent elevation in the PM
If (+) Cushing syndrome screening:
How do you differentiate between ACTH dependent vs independent?
Test for serum ACTH:
Low ACTH: ACTH independent
** The true diagnostic difficulty lies in distinguishing Cushing disease from the ectopic ACTH syndrome for patients who have high serum ACTH levels.