Endocrine - The Adrenal Gland Flashcards
What is Cushing’s syndrome?
A collection of signs and symptoms that occur when a patient has long term exposure to cortisol
Causes of Cushing’s syndrome
- Exogenous steroids (in patients on long term high dose steroid medications)
- Cushing’s Disease (a pituitary adenoma releasing excessive ACTH)
- Adrenal Adenoma (a hormone secreting adrenal tumour)
- Paraneoplastic Cushing’s
Describe paraneoplastic Cushing’s
Excess ACTH is released from a cancer (not of the pituitary) and stimulates excessive cortisol release. ACTH from somewhere other than the pituitary is called “ectopic ACTH”. Small Cell Lung Cancer is the most common cause of paraneoplastic Cushing’s.
Signs and symptoms of Cushing’s syndrome
Round in the middle with thin limbs:
- Round “moon” face
- Central Obesity
- Abdominal striae
- Cervical fat pad
- Proximal limb muscle wasting
High levels of stress hormone:
- Hypertension
- Cardiac hypertrophy
- Hyperglycaemia (Type 2 Diabetes)
- Depression
- Insomnia
- Acne
- Amenorrhoea
Extra effects:
- Osteoporosis
- Easy bruising and poor skin healing
Investigations for Cushing’s syndrome
- Dexamethasone suppression tests
- 24 hour urinary free cortisol can be used as an alternative to the dexamethasone suppression test to diagnose Cushing’s syndrome but does not indicate the underlying cause and is cumbersome to carry out.
- FBC (raised white cells) and electrolytes (potassium may be low if aldosterone is also secreted by an adrenal adenoma)
- MRI brain for pituitary adenoma
- Chest CT for small cell lung cancer
- Abdominal CT for adrenal tumours
Describe the dexamethasone suppression test
To perform the test the patient takes a dose of dexamethasone (a synthetic glucocorticoid steroid) at night (i.e. 10pm) and their cortisol and ACTH is measured in the morning (i.e. 9am). The intention is the find out whether the dexamethasone suppresses their normal morning spike of cortisol.
Treatment of Cushing’s syndrome
The main treatment is to remove the underlying cause (surgically remove the tumour)
- Trans-sphenoidal (through the nose) removal of pituitary adenoma
- Surgical removal of adrenal tumour
- Surgical removal of tumour producing ectopic ACTH
If surgical removal of the cause is not possible another option is to remove both adrenal glands and give the patient replacement steroid hormones for life.
Ketoconazole, metyrapone, fluconazole to decrease cortisol
What is adrenal insufficiency?
Adrenal insufficiency is where the adrenal glands do not produce enough steroid hormones, particularly cortisol and aldosterone.
Describe Addison’s disease
Addison’s Disease refers to the specific condition where the adrenal glands have been damaged, resulting in a reduction in the secretion of cortisol and aldosterone. This is also called Primary Adrenal Insufficiency. The most common cause is autoimmune.
Describe Secondary Adrenal Insufficiency
Secondary Adrenal Insufficiency is a result of inadequate ACTH stimulating the adrenal glands, resulting in low cortisol release. This is the result of loss or damage to the pituitary gland.
Causes of secondary adrenal insufficiency
This can be due to surgery to remove a pituitary tumour, infection, loss of blood flow or radiotherapy. There is also a condition called Sheehan’s syndrome where massive blood loss during childbirth leads to pituitary gland necrosis.
Describe tertiary adrenal insufficiency
Tertiary Adrenal Insufficiency is the result of inadequate CRH release by the hypothalamus. This is usually the result of patients being on long term oral steroids (for more than 3 weeks) causing suppression of the hypothalamus.
When the exogenous steroids are suddenly withdrawn the hypothalamus does not “wake up” fast enough and endogenous steroids are not adequately produced. Therefore long term steroids should be tapered slowly to allow time for the adrenal axis to regain normal function.
Signs and symptoms of adrenal insufficiency
Signs
- Bronze hyperpigmentation to skin (ACTH stimulates melanocytes to produce melanin)
- Hypotension (particularly postural hypotension)
Symptoms
- Fatigue
- Nausea
- Cramps
- Abdominal pain
- Reduced libido
Investigations for adrenal insufficiency
- Hyponatraemia (a key biochemical clue. Sometimes the only presenting feature of adrenal insufficiency)
- Hyperkalaemia
- Early morning cortisol has a role but is often falsely normal
- A short synacthen test is the test of choice to diagnose adrenal insufficiency
- ACTH
- Adrenal autoantibodies are present in 80% of autoimmune adrenal insufficiency: adrenal cortex antibodies and 21-hydroxylase antibodies
- CT / MRI adrenals if suspecting an adrenal tumour, haemorrhage or other structural pathology (not recommended by NICE for autoimmune adrenal insufficiency)
- MRI pituitary gives further information about pituitary pathology
How does testing ACTH levels differentiate between primary and secondary adrenal insufficiency?
In primary adrenal failure the ACTH level is high as the pituitary is trying very hard to stimulate the adrenal glands without any negative feedback in the absence of cortisol. In secondary adrenal failure the ACTH level is low as the reason the adrenal glands are not producing cortisol is that they are not being stimulated by ACTH.
