Adrenal Gland And Hormones Flashcards
What is the difference between primary and secondary insufficiency
Primary - problems with the gland itself - Addison's disease - congenital adrenal hyperplasia (CAH) - adrenal TB/malignancy Secondary - everything else that affects the adrenal gland - lack of ACTH stimulation - iatrogenic (excess exogenous steroid) - pituitary/hypothalamic disorder
Describe Addison’s disease
Autoimmune destruction of the adrenal cortex
- over 90% is destroyed before symptoms are ready
- autoantibodies are found in around 70% of cases
Associated with other autoimmune diseases
- T1DM, autoimmune thyroid diseases, pernicious anaemia
What are the clinical features of Addison’s disease?
Anorexia Weight loss Fatigue/lethargy Dizziness and low BP Abdominal pain Vomiting Diarrhoea Skin pigmentation
How is primary adrenal insufficiency diagnosed?
Biochemistry
- increased potassium and decreased sodium
- hypoglycaemia
Short synACTHen test
Measure ACTH levels
- they should be very high (causes the skin pigmentation)
Renin/aldosterone levels
- renin will be very high and aldosterone will be decreased
Adrenal autoantibodies
What effect does decreased cortisol have on the HPA axis?
Lack of cortisol means CRH and ACTH are not inhibited and levels will be very high
Describe the short synACTHen test.
Measure plasma cortisol before and 30 mins after an IV ACTH injection
Normal - baseline >250nmol/l, post ACTH >480
Addison’s - baseline will be very low and remain low even after ACTH dosage
What are the actions of cortisol
Promotes lipolysis Counteracts insulin - decreases peripheral uptake of glucose Decreased amino acid uptake by muscle Increased gluconeogensis Reduces bone formation Slows the immune systems inflammatory response Increases appetite Maintains BP and CV function
How is primary adrenal insufficiency managed?
Hydrocortisone as cortisol replacement
- give IV if very unwell
- 15-30mg tablets daily in divided doses, to try and mimic the diurnal rhythm
Fludrocortisone as aldosterone replacement
- careful monitoring of BP and plasma potassium
Education
- sick day rules - double hydrocortisone dose when very unwell
- can’t suddenly stop
- need to wear identification
Why should you not stop taking fludrocortisone and hydrocortisone?
You will suffer from acute adrenal insufficiency, as the body doesn’t have time to produce its own hormones instead.
Causes all the symptoms of adrenal insufficiency, magnified and in a smaller space of time - can result in death in serious cases
What are the most common causes of secondary adrenal insufficiency?
Pituitary/hypothalamic diseases
- tumour, surgery or radiotherapy
Exogenous steroid use - most common cause
What does exogenous steroids do to the HPA axis, and give some examples of steroids.
They have a negative effect on CRH and ACTH Examples - high dose prednisolone - dexamethasone - inhaled corticosteriod
What are the clinical features of secondary adrenal insufficiency?
Similar to Addisons, EXCEPT
- the skin doesn’t darken (ACTH level are not increased)
- aldosterone levels are normal (production regulated by RAS system)
How is secondary adrenal insufficiency treated?
Given hydrocortisone to replace the cortisol loss
Fludorocortisone isn’t needed due to intact aldosterone levels
Briefly describe Cushing’s syndrome.
Excess cortisol secretion
High mortality
More common in women (ages 20-40)
Clinical features of cortisol excess.
Easy bruising Facial plethora Striae Proximal myopathy Hypertension Thinning of skin Moon face Poor wound healing Oestoporosis Increases appetite + weight gain Increased susceptibility to infection
What are the two categories of Cushing’s syndrome?
ACTH dependent (secondary)
- pituitary adenoma (68% - Cushing’s disease)
- ectopic ACTH (12%)
- ectopic CRH (
How is it established that a patient has cortisol excess?
Dexamethasone suppression test - should suppress the cortisol production
24hr urinary free cortisol
Late night salivary cortisol
How is the source of the cortisol excess established?
The ACTH is measured
- if it can’t be detected, the problem is in the adrenal gland (constantly pumping out cortisol inhibited ) = adrenal CT scan
- if it is normal/high, a CRH stimulation test is performed
CRH stimulation test
- if there is no change in the ACTH levels, it’s ectopic ACTH (as the tissue can still manage any changes in CRH) = CT scan to find
- a large increase means the problem the pituitary, and the remaining healthy tissue is forced to produce more ACTH = pituitary MRI
How is Cushing’s disease managed with surgery?
Removal of ACTH source
- ectopic
- transsphenoidal pituitary surgery
Laparoscopic adrenalectomy
How is Cushing’s managed medically?
Methyraprone/ketoconazole
- inhibit cortisol production
Should only be used as short term measure until surgery can be performed
Describe iatrogenic Cushing’s syndrome.
Commonest cause of cortisol excess
Due to prolonged high dose steroid therapy
- e.g. Asthma, rheumatoid arthritis, IBS and transplants
The body thinks that these steroid are cortisol (because they act like cortisol) and that you have way too much of them = Cushing’s
What are the main problems with iatrogenic Cushing’s syndrome?
Chronic suppression of pituitary ACTH production and adrenal atrophy - no endogenous cortisol
- can’t respond to stress
- need extra doses when I’ll
- can’t stop suddenly
- need to gradually withdraw over 4-6 weeks
What is essential and secondary hypertension?
Essential (90%) - has no known cause
Secondary (10%) - secondary to another disease (e.g. Renal disease, aldosterone excess, drug induced)
- more likely in the young and resistant hypertension
Hypertension can result from the adrenal gland, why?
Aldosterone is produced in the middle layer of the cortex (is a mineralocorticoid)
