Addison's disease Flashcards
What is addison’s disease?
Addison’s disease is the most common form of adrenal insufficiency.
Adrenal insufficiency occurs where there is destruction of the adrenal cortex and reduced output of adrenal hormones
What are the two types of adrenal insufficiency?
- Primary hypoadrenalism
- Secondary hypoadrenalism
What is primary hypoadrenalism?
In primary hypoaldosteronism conditions, there is the destruction of the adrenal cortex. The presentation is notoriously varied and vague. It is potentially fatal if untreated. There will be a lack of secretion of cortisol, aldosterone and sex hormone.
Usually due to autoimmune disease
What is secondary hypoadrenalism?
Due to inadequate secretion of pituitary hormones and thus reduced stimulation of the adrenal glands
aldosterone secretion may remain at normal levels due to stimulation from pituitary independent mechanisms – namely via angiotensin II.
inadequate ACTH from the pituitary gland, leading to a lack of stimulation of the adrenal glands
What is tertiary Addison’s disease?
inadequate corticotropin releasing hormone (CRH) from the hypothalamus, resulting in reduced cortisol and aldosterone secretion
What hormone stimulates the pituitary to release ACTH?
CRH (corticotrophin releasing hormone)
What is the epidemiology of Addison’s disease?
Addison’s disease is rare – it has an incidence of 3-4 per 1,000,000 per year, and a prevalence of 40-60 per 1,000,000.
It is more common in women
Typical age of onset 30 to 50
>90% of cases are a result of autoimmune disease
The remainder are mostly a result of TB.
What is the most common cause of Addison’s disease?
autoimmune attack of the adrenal glands
Give 5 causes of secondary adrenal insufficiency:
1) tumours e.g. pituitary adenomas
2) surgery to the pituitary
3) radiotherapy
4) Sheehan’s syndrome
5) trauma
What is Sheehan’s syndrome?
major post-partum haemorrhage causing avascular necrosis of the pituitary gland
What is the main cause of tertiary adrenal insufficiency?
long term exogenous steroid use
Describe how long term exogenous steroid use can cause tertiary adrenal insufficiency:
exogenous steroid use causes suppression to the hypothalamus via negative feedback
Explain why it is important to slowly withdraw steroid medications:
sudden withdrawal may mean the hypothalamus does not respond fast enough to the sudden lack of negative feedback, meaning the axis does not start up quick enough leading to insufficiency
Give 11 presentations associated with adrenal insufficiency:
1) fatigue
2) muscle weakness
3) muscle cramps
4) dizziness and fainting
5) thirst and craving salt
6) weight loss
7) abdominal pain
8) depression
9) reduced libido
10) bronze hyperpigmentation
11) hypotension and postural hypotension
When would bronze hyperpigmentation be seen in adrenal insufficiency?
where there are high levels of ACTH which stimulates melanocytes to produce melanin
Where is bronze hyperpigmentation usually seen in Addison’s disease?
1) skin creases (palms of hands especially)
2) lips
3) oral mucosa
What is the key U+E finding associated with adrenal insufficiency?
hyponatraemia
(Low blood sodium level)
Other than hyponatraemia, give 4 other U+E findings that are associated with adrenal insufficiency:
1) hyperkalaemia
2) hypoglycaemia
3) raised urea and creatinine due to dehydration
4) hypercalcaemia
Will ACTH be high or low in Addison’s disease?
high
Will ACTH be high or low in secondary/tertiary adrenal insufficiency?
Low
Give 2 antibodies that are associated with Addison’s disease with autoimmune causes:
1) adrenal cortex antibodies
2) 21-hydroxylase antibodies
What is the gold standard investigation for diagnosing Addison’s disease?
short synacthen test
Describe the process of the short synacthen test: (2)
1) give a dose of synacthen (synthetic ACTH)
2) check blood cortisol before and 30 and 60 mins after the dose
What result would be expected from the short synacthen test in healthy individuals?
cortisol should at least double
