Disorders of the Adrenal Cortex Flashcards
How can high levels of ACTH cause excess pigmentation?
ACTH is derived from POMC
The MSH sequence is contained within ACTH
Therefore when there are high levels of ACTH, there are some signs of MSH
When do you get excess levels of ACTH?
Low/no negative feedback from cortisol to the anterior pituitary gland. An example would be in Addisons disease
What is Cushing’s syndrome?
Increased activity of adrenal cortex due to tumour (causes increased levels of cortisol)
Ectopic secretion of ACTH
What are the signs and symptoms of a deficiency in Cortisol?
Low Glucose
Weight loss
Hypotension
Nausea
What are the signs and symptoms of excess Cortisol?
High Glucose
Weight gain
Increased appetite
Hypertension
What is Addison’s disease?
Endocrine disorder where the adrenal glands do not produce enough Glucocorticoids or mineralocorticoids
What can cause Addison’s disease?
Autoimmune destruction of the Adrenal glands
Disorder of pituitary/hypothalamus so reduces secretion of ACTH causing reduces glucocorticoids
What are the symptoms of an Addison’s crisis?
Nausea Vomiting Coma Confusion Dehydration Fever
Why do you get increased pigmentation in people with Addison’s disease?
Because there is ACTH mediated melanocyte stimulation.
How does the Dexamethasone suppression test work?
Dexamethasone is a potent synthetic steroid
It would suppress secretion of ACTH (and therefore cortisol) if given
Does Dexamethasone suppress Cortisol release in people with Cushings?
In more than 50% of cases
The diseased pituitary is still sensitive to potent synthetic steroids
Does Dexamethasone suppress secretion of ACTH from ectopic sites or tumours?
Not ususally
What is Synacthen?
A synthetic analogue of ACTH
How can you use Synacthen to test for Addison’s disease?
Administer intramuscularly
Normally increase in plasma cortisol by 200nmol/L (or more)
If not, then the patient may have Addison’s disease
How can Cortisol have weak androgen and mineralcorticoid properties?
There is sequence homology in the hormone-binding region of the receptors
Cortisol will bind to the mineralocorticoid and androgen receptors with low affinity.
Binding may become significant when high levels of the hormone are present
