Week 12 - Addison's, APKD, Cushing's Flashcards
what is adrenal insufficiency
where the adrenal glands do not produce enough steroid hormones, particularly cortisol and aldosterone
what does Addison’s disease refer specifically to
when the adrenal glands have been damaged resulting in reduced cortisol and aldosterone secretion.
what is primary adrenal insufficiency
Addison’s
what is the most common cause of Addison’s disease
autoimune
what does secondary adrenal insufficiency result from
inadequate adrenocorticotropic hormone (ACTH) and a lack of stimulation of the adrenal glands leading to low cortisol.
what is secondary adrenal insufficinecy a result of
loss or damage to the pituitary glands
what are the causes of secondary adrenal insufficinecy
Tumours (e.g., pituitary adenomas)
Surgery to the pituitary
Radiotherapy
Sheehan’s syndrome (where major post-partum haemorrhage causes avascular necrosis of the pituitary gland)
Trauma
what does tertiary adrenal insufficiency result from
corticotropin-releasing hormone (CRH) release by the hypothalamus
what is tertiary adrenal insufficiency usually caused by
patients taking long-term oral steroids causing suppression of the hypothalamus (via negative feedback)
what happens when the exogenous steroids (originating from outside the body) are suddenly withdrawn
the hypothalamus does not ‘wake up’ fast enough, and endogenous steroids (originating from inside the body) are not adequately produced.
what are the symptoms of adrenal insufficiency
Fatigue
Muscle weakness
Muscle cramps
Dizziness and fainting
Thirst and craving salt
Weight loss
Abdominal pain
Depression
Reduced libido
what are the two signs of adrenal insufficiency
Bronze hyperpigmentation of the skin, particularly in creases (ACTH stimulates melanocytes to produce melanin)
Hypotension (particularly postural hypotension – with a drop of more than 20 mmHg on standing)
what is the bronze hyperpigmentation of the skin caused by
excessive ACTH stimulating melanocytes to produce melanin.
it mainly affects skin creases, scars, lips and buccal mucosa
what is a key biochemical feature in adrenal insufficiency
hyponataemia (low sodium)
what are the other key biochemical findings that may be seen in adrenal insufficiency
Hyperkalaemia (high potassium)
Hypoglycaemia (low glucose)
Raised creatinine and urea due to dehydration
Hypercalcaemia (high calcium)
what is the test of choice for diagnosing adrenal insufficiency
the short Synacthen test
is the ACTH level high or low in primary adrenal insufficiency and why
the ACTH level is high in PAI as the pituitary is producing lots of ACTH without negative feedback in the absence of cortisol.
what does the ACTH level look like in secondary adrenal failure
the ACTH level is low
what antibodies my be present in autoimmune adrenal insufficiency
Adrenal cortex antibodies
21-hydroxylase antibodies
what can be helpful if you are suspecting structural pathology but not routinely required
CT or MRI
what does the short synacthen test involve
giving a dose of synacthen which is synthetic ACTH
the blood cortisol is checked before and 30-60 minutes after the dose
the synthetic ACTH will stimulate healthy adrenal glands to produce cortisol.
what should be levels of cortisol do in the SST
should at least double
what does a failure of cortisol to double indicate in the short synacthen test
Primary adrenal insufficiency (Addison’s disease)
or
Very significant adrenal atrophy after a prolonged absence of ACTH in secondary adrenal insufficiency
what is the mainstay of treatment in adrenal insufficiency
replacement steroids titrated to signs, symptoms and electrolytes.