Disorders Of Adrenocortical Function Flashcards Preview

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Flashcards in Disorders Of Adrenocortical Function Deck (22)
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1
Q

What 2 factors may lead to an under active adrenal cortex?

A
  • Autoimmune destruction of adrenal cortex

- Disorders in pituitary or hypothalamus resulting in decreased ACTH or CRH secretion

2
Q

What are the possible causes of an increased activity of the adrenal cortex?

A
  • Increased activity due to tumour of adrenal gland (ADENOMA)
  • Disorder of pituitary gland resulting in increased ACTH secretion (PITUITARY ADENOMA)
  • ECTOPIC secretion of ACTH
3
Q

What is the difference between Cushing’s syndrome and Cushing’s disease?

A
  • Cushing’s SYNDROME is increased levels of cortisol due to adenoma/adrenal hyperplasia
  • Cushing’s DISEASE is increased levels of cortisol as a result of a pituitary adenoma which causes increased secretion of ACTH
4
Q

Explain how congenital adrenal hyperplasia arises

A
  • Lack of cortisol at birth
  • Large amounts of ACTH secreted from anterior pituitary
  • Pituitary is NOT subject to feedback control
  • TROPHIC effects on adrenal cortex resulting in an increase in number of cells (hyperplasia)
5
Q

Explain how an increase in cortisol levels can lead to “steroid diabetes”

A
  • Cortisol stimulates hepatic glycogenolysis and gluconeogenesis and proteolysis of muscles
  • Results in an increase in blood glucose levels (hyperglycaemia)
  • May have associated polyuria and polydipsia
6
Q

What are the main signs and symptoms of a patient with Cushing’s syndrome?

A
  • Moon shaped plethoric face
  • Increased adipose tissue in abdomen
  • Thin arms and legs (muscle wastage)
  • Purple striae (weakened skin)
  • Easy bruising
  • Possible hyperglycaemia
7
Q

Why may a person with Cushing’s syndrome also have hypertension?

A
  • Cortisol has a similar structure to mineralocorticoids
  • Cortisol can bind to mineralocorticoid receptors and stimulate the uptake of Na+ (and therefore water) into tissues and blood vessels causing fluid retention
8
Q

How could a patient who does not have Cushing’s syndrome still exhibit the signs and symptoms?

A

May have had long term treatment with glucocorticoids for various chronic inflammatory conditions e.g. Asthma, skin conditions

9
Q

What are the clinical signs and symptoms of a patient in Addisonian crisis?

A
  • Nausea
  • Vomiting
  • Confusion
  • Hypotension
  • Extreme dehydration
  • Fever
  • Possible coma
10
Q

Why might a patient with Addison’s disease show hyperpigmentation?

A
  • Low cortisol levels stimulate secretion of CRH and thus ACTH
  • ACTH has α-MSH receptor complementarity
  • Excess ACTH can bind to α-MSH receptors on melanocytes, stimulating the secretion of melanin which leads to pigmentation
11
Q

Why do patients with Addison’s experience extreme dehydration and postural hypotension?

A
  • Autoimmune destruction of adrenal cortex results in loss of mineralocorticoid production
  • Decreased Na+ uptake, therefore decreased fluid retention
  • This also causes low blood pressure
12
Q

How would you treat a patient in Addisonian crisis?

A
  • Intravenous cortisol injections
  • Fluid replacement
  • IV saline with DEXTROSE (as patient may also be hypoglycaemic)
13
Q

What clinical tests could you use to investigate adrenocortical function?

A
  • Dexamethasone suppression test

- Synacthen stimulation test

14
Q

Describe how a Dexamethasone test can be used to distinguish between Cushing’s syndrome and Cushing’s disease

A
  • Dexamethasone suppresses ACTH secretion from the pituitary gland
  • If after administering Dexamethasone the blood cortisol levels fall, this indicates Cushing’s disease via an ACTH secreting pituitary tumour
  • If levels of cortisol remain normal then the cause must be either a cortisol secreting adrenal tumour or an ectopic secretion of ACTH
15
Q

Describe how a Synacthen test can be used to diagnose Addison’s disease

A
  • Administer synthetic ACTH intramuscularly
  • Rise in blood cortisol levels would indicate a normal patient
  • No change in cortisol levels would indicate Addison’s disease
16
Q

Explain why cortisol (a glucocorticoid) can bind to mineralocorticoid receptors

A
  • There is sequence HOMOGENY in the hormone binding regions of the receptors (~64%)
  • This allows cortisol to bind to mineralocorticoid receptors with low affinity
  • This effect becomes more apparent when there is an excess in cortisol
17
Q

What is the role of aldosterone?

A

Stimulates Na+ reabsorption in the kidneys in exchange for K+, therefore increasing Na+ and water retention and loss of K+

18
Q

Where are androgens secreted from? Give an example.

A
  • Secreted from the zona reticularis of the adrenal cortex

- Example includes dehydroepiandrosterone

19
Q

What are the effects of androgens?

A
  • Stimulate growth and development of male genital tract and male secondary sexual characteristics (such as height, facial and body hair and lowering pitch of voice)
  • Also have anabolic actions, especially on muscle protein
20
Q

What are the three main regions of steroid receptors?

A
  • Hormone binding region (hydrophobic)
  • DNA binding region (rich in cysteine and basic amino acids)
  • Variable region
21
Q

What clinical problems may arise from hypoactivity of the adrenal cortex?

A
  • Addison’s disease (due to decrease in cortisol secretion)

- Hypotension (due to decrease in mineralocorticoid secretion)

22
Q

What factors may initiate a patient with Addison’s disease to enter Addisonian crisis?

A
  • Stress (may be induced by lack of steroid treatment)
  • Trauma
  • Severe infection