Cushing's syndrome Flashcards
What is Cushing’s syndrome?
Cushing’s syndrome refers to the features of prolonged high levels of glucocorticoids (e.g., cortisol) in the body.
What are the two groups of corticosteroid hormones?
The two groups are:
* Glucocorticoids (e.g., cortisol)
* Mineralocorticoids (e.g., aldosterone)
What is Cushing’s disease?
Cushing’s disease refers to a pituitary adenoma secreting excessive ACTH, which stimulates excessive cortisol release from the adrenal glands.
What is the most common cause of Cushing’s syndrome?
The most common cause is prolonged use of exogenous corticosteroids (e.g., prednisolone or dexamethasone).
What are the key features of Cushing’s syndrome?
Key features include:
* Round face (‘moon face’)
* Central obesity
* Abdominal striae (stretch marks)
* Buffalo hump (fat pad on the upper back)
* Proximal limb muscle wasting
* Male pattern facial hair in women (hirsutism)
* Easy bruising and poor skin healing
* Hyperpigmentation (in Cushing’s disease)
What additional effects can occur in Cushing’s syndrome?
Additional effects include:
* Hypertension
* Cardiac hypertrophy
* Type 2 diabetes
* Dyslipidaemia
* Osteoporosis
* Mental health issues (e.g., anxiety, depression, insomnia, and rarely psychosis)
How can you remember the causes of Cushing’s syndrome?
Use the ‘CAPE’ mnemonic:
* C – Cushing’s disease (pituitary adenoma)
* A – Adrenal adenoma
* P – Paraneoplastic syndrome
* E – Exogenous steroids
What is paraneoplastic Cushing’s syndrome?
Paraneoplastic Cushing’s syndrome occurs when a tumor releases ACTH (ectopic ACTH), stimulating excessive cortisol production. Small-cell lung cancer is the most common cause.
How does excess ACTH affect the skin?
High ACTH levels cause skin pigmentation by stimulating melanocytes to produce melanin, which is seen in Cushing’s disease and primary adrenal insufficiency.
What is the purpose of dexamethasone suppression tests?
Dexamethasone suppression tests help diagnose Cushing’s syndrome caused by internal factors (e.g., pituitary adenomas), not caused by exogenous steroids.
What is the normal response to dexamethasone?
The normal response is suppression of cortisol levels due to negative feedback on the hypothalamus and pituitary, reducing ACTH and cortisol production.
What are the three types of dexamethasone suppression tests?
The three types are:
* Low-dose overnight test (screening for Cushing’s syndrome)
* Low-dose 48-hour test (diagnosing suspected Cushing’s syndrome)
* High-dose 48-hour test (determining the cause of confirmed Cushing’s syndrome)
What is measured during dexamethasone suppression tests?
Cortisol levels are measured, with the response to dexamethasone indicating whether Cushing’s syndrome is present, and the type of Cushing’s syndrome (pituitary, adrenal, or ectopic).
What do the ACTH levels indicate in Cushing’s syndrome?
ACTH levels indicate:
* Low ACTH: Suggests an adrenal adenoma or exogenous steroids.
* High ACTH: Suggests Cushing’s disease or ectopic ACTH production.
What are some other investigations for Cushing’s syndrome?
Other investigations may include:
* 24-hour urinary free cortisol
* Full blood count (may show high white blood cell count)
* U&Es (low potassium in adrenal adenoma cases)
* MRI brain for pituitary adenoma
* CT chest for small-cell lung cancer
* CT abdomen for adrenal tumors
What is the main treatment for Cushing’s syndrome?
The main treatment is to remove the underlying cause, such as:
* Trans-sphenoidal removal of pituitary adenoma
* Surgical removal of adrenal tumor
* Surgical removal of ectopic ACTH-producing tumor (e.g., small-cell lung cancer)
What happens if both adrenal glands are removed in Cushing’s syndrome treatment?
Removal of both adrenal glands leads to Nelson’s syndrome, which causes skin pigmentation, bitemporal hemianopia, and a lack of other pituitary hormones.
What is the role of metyrapone in treating Cushing’s syndrome?
Metyrapone reduces cortisol production in the adrenal glands and is occasionally used in treating Cushing’s syndrome when surgical options are not feasible.
