Disorders of Adrenocortical Function

Question 1

What gives rise to Cushing’s syndrome?

Answer 1

Hyperactivity of adrenal cortex leading to increased secretion of cortisol

Question 2

Why could a patient with Cushing’s syndrome have think arms and legs?

Answer 2

Increased muscle proteolysis

Question 3

Why do patients with Cushing’s syndrome have a moon face and buffalo hump?

Answer 3

Redistribution of fat in abdomen, neck and face

Question 4

Why do patients with Cushing’s syndrome have purple striae?

Answer 4

Increased proteolysis in skin

Question 5

Why do patients with Cushing’s syndrome have an increased susceptibility to bacterial infections?

Answer 5

Cortisol is immunosuppressive

Question 6

What is Addison’s diseased?

Answer 6

Decreased activity of adrenal cortex

Question 7

What may Addison’s disease be due to?

Answer 7

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)

Question 8

What are the clinical tests of adrenocortical function?

Answer 8

Measuring plasma cortisol and ACTH levels and the 24hr urinary excretion of cortisol and its breakdown products

Dexamethasone suppression test

ACTH stimulation test

Question 9

What is dexamethasone?

Answer 9

A potent synthetic steroid that would normally suppress the secretion of ACTH and thus cortisol

Question 10

What is the dexamethosone suppression test?

Answer 10

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.

Question 11

What suppression test result is characteristic of Cushing’s disease?

Answer 11

Suppression of cortisol by >50% because the pituitary retains some negative feedback control

Question 12

What is suspected if suppression of cortisol does not occur as a result of the dexamethosone suppression test but ACTH levels are elevated?

Answer 12

Ectopic or adrenal tumour

Question 13

What is suspected if suppression of cortisol does not occur as a result of the dexamethosone suppression test but ACTH levels are low?

Answer 13

Primary hypercortisolism

i.e. the hypercortisolism is not driven by ACTH hypersecretion

Question 14

What is the ACTH stimulation test?

Answer 14

Used to assess the function of the adrenal glands stress response by measuring the adrenal response to adrenocorticotropic hormone

Question 15

What a normal response to the ACTH stimulation test?

Answer 15

Increased plasma cortisol by >200 nmol/L

Question 16

How is Addison’s disease diagnosed from the ACTH stimulation test?

Answer 16

Plasma cortisol not increased

Question 17

How is congenital adrenal hyperplasia caused?

Answer 17

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

Question 18

What is the most common form of congenital adrenal hyperplasia?

Answer 18

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

Question 19

What is Conn’s syndrome?

Answer 19

Primary hyperaldosteronism

Question 20

What would be the causes of unilateral and bilateral Conn’s syndrome?

Answer 20

Unilateral - adenoma

Bilateral - familial hyperaldosteronism (genetic)

Question 21

In Conn’s syndrome, does decreased renin also lead to a decrease in aldosterone?

Answer 21

No - diagnostic criteria for the disease

Normally decreased renin -> decreased aldosterone

Question 22

Why will cortisol also bind to the mineralocorticoid and androgen receptors with low affinity?

Answer 22

Percentage homology - 64% and 62% respectively

Binding may be more significant when high levels of the hormone are present

Question 23

Over secretion of adrenal androgens will produce what effects in females?

Answer 23

Excessive body hair growth, acne, menstrual problems, virilisation, increased muscle bulk and a deepening voice