Disorders Of Adrenocortical Function Flashcards
What 2 factors may lead to an under active adrenal cortex?
- Autoimmune destruction of adrenal cortex
- Disorders in pituitary or hypothalamus resulting in decreased ACTH or CRH secretion
What are the possible causes of an increased activity of the adrenal cortex?
- Increased activity due to tumour of adrenal gland (ADENOMA)
- Disorder of pituitary gland resulting in increased ACTH secretion (PITUITARY ADENOMA)
- ECTOPIC secretion of ACTH
What is the difference between Cushing’s syndrome and Cushing’s disease?
- 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
Explain how congenital adrenal hyperplasia arises
- 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)
Explain how an increase in cortisol levels can lead to “steroid diabetes”
- 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
What are the main signs and symptoms of a patient with Cushing’s syndrome?
- Moon shaped plethoric face
- Increased adipose tissue in abdomen
- Thin arms and legs (muscle wastage)
- Purple striae (weakened skin)
- Easy bruising
- Possible hyperglycaemia
Why may a person with Cushing’s syndrome also have hypertension?
- 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
How could a patient who does not have Cushing’s syndrome still exhibit the signs and symptoms?
May have had long term treatment with glucocorticoids for various chronic inflammatory conditions e.g. Asthma, skin conditions
What are the clinical signs and symptoms of a patient in Addisonian crisis?
- Nausea
- Vomiting
- Confusion
- Hypotension
- Extreme dehydration
- Fever
- Possible coma
Why might a patient with Addison’s disease show hyperpigmentation?
- 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
Why do patients with Addison’s experience extreme dehydration and postural hypotension?
- Autoimmune destruction of adrenal cortex results in loss of mineralocorticoid production
- Decreased Na+ uptake, therefore decreased fluid retention
- This also causes low blood pressure
How would you treat a patient in Addisonian crisis?
- Intravenous cortisol injections
- Fluid replacement
- IV saline with DEXTROSE (as patient may also be hypoglycaemic)
What clinical tests could you use to investigate adrenocortical function?
- Dexamethasone suppression test
- Synacthen stimulation test
Describe how a Dexamethasone test can be used to distinguish between Cushing’s syndrome and Cushing’s disease
- 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
Describe how a Synacthen test can be used to diagnose Addison’s disease
- Administer synthetic ACTH intramuscularly
- Rise in blood cortisol levels would indicate a normal patient
- No change in cortisol levels would indicate Addison’s disease
Explain why cortisol (a glucocorticoid) can bind to mineralocorticoid receptors
- 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
What is the role of aldosterone?
Stimulates Na+ reabsorption in the kidneys in exchange for K+, therefore increasing Na+ and water retention and loss of K+
Where are androgens secreted from? Give an example.
- Secreted from the zona reticularis of the adrenal cortex
- Example includes dehydroepiandrosterone
What are the effects of androgens?
- 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
What are the three main regions of steroid receptors?
- Hormone binding region (hydrophobic)
- DNA binding region (rich in cysteine and basic amino acids)
- Variable region
What clinical problems may arise from hypoactivity of the adrenal cortex?
- Addison’s disease (due to decrease in cortisol secretion)
- Hypotension (due to decrease in mineralocorticoid secretion)
What factors may initiate a patient with Addison’s disease to enter Addisonian crisis?
- Stress (may be induced by lack of steroid treatment)
- Trauma
- Severe infection
