Disorders of Adrenocortical Function Flashcards
What gives rise to Cushing’s syndrome?
Hyperactivity of adrenal cortex leading to increased secretion of cortisol
Why could a patient with Cushing’s syndrome have think arms and legs?
Increased muscle proteolysis
Why do patients with Cushing’s syndrome have a moon face and buffalo hump?
Redistribution of fat in abdomen, neck and face
Why do patients with Cushing’s syndrome have purple striae?
Increased proteolysis in skin
Why do patients with Cushing’s syndrome have an increased susceptibility to bacterial infections?
Cortisol is immunosuppressive
What is Addison’s diseased?
Decreased activity of adrenal cortex
What may Addison’s disease be due to?
Diseases of adrenal cortex (eg autoimmune destruction) - affects glucocorticoids and mineralocorticoids
Disorders in pituitary or hypothalamus that leads to decreased secretion of ACTH or CRH (affects glucocorticoids)
What are the clinical tests of adrenocortical function?
Measuring plasma cortisol and ACTH levels and the 24hr urinary excretion of cortisol and its breakdown products
Dexamethasone suppression test
ACTH stimulation test
What is dexamethasone?
A potent synthetic steroid that would normally suppress the secretion of ACTH and thus cortisol
What is the dexamethosone suppression test?
The dexamethasone suppression test (DST) is used to assess adrenal gland function by measuring how cortisol levels change in response to an injection of dexamethasone. It is typically used to diagnose Cushing’s syndrome.
What suppression test result is characteristic of Cushing’s disease?
Suppression of cortisol by >50% because the pituitary retains some negative feedback control
What is suspected if suppression of cortisol does not occur as a result of the dexamethosone suppression test but ACTH levels are elevated?
Ectopic or adrenal tumour
What is suspected if suppression of cortisol does not occur as a result of the dexamethosone suppression test but ACTH levels are low?
Primary hypercortisolism
i.e. the hypercortisolism is not driven by ACTH hypersecretion
What is the ACTH stimulation test?
Used to assess the function of the adrenal glands stress response by measuring the adrenal response to adrenocorticotropic hormone
What a normal response to the ACTH stimulation test?
Increased plasma cortisol by >200 nmol/L
How is Addison’s disease diagnosed from the ACTH stimulation test?
Plasma cortisol not increased
How is congenital adrenal hyperplasia caused?
Genetic defect in enzymes required for synthesis of corticosteroid hormones
Lack of cortisol -> pituitary not subjected to negative feedback control -> secretes large amounts of ACTH -> enlargement of adrenal cortex
What is the most common form of congenital adrenal hyperplasia?
Deficiency of 21-hydroxylase
Less glucocorticoid and mineralocorticoid production
The precursor of these hormones is diverte to more androgen synthesis -> genital ambiguity in females and salt-wasting crises
What is Conn’s syndrome?
Primary hyperaldosteronism
What would be the causes of unilateral and bilateral Conn’s syndrome?
Unilateral - adenoma
Bilateral - familial hyperaldosteronism (genetic)
In Conn’s syndrome, does decreased renin also lead to a decrease in aldosterone?
No - diagnostic criteria for the disease
Normally decreased renin -> decreased aldosterone
Why will cortisol also bind to the mineralocorticoid and androgen receptors with low affinity?
Percentage homology - 64% and 62% respectively
Binding may be more significant when high levels of the hormone are present
Over secretion of adrenal androgens will produce what effects in females?
Excessive body hair growth, acne, menstrual problems, virilisation, increased muscle bulk and a deepening voice
