Endocrine - Cushing's Syndrome Flashcards
What is Cushing’s syndrome?
Syndrome in which there is prolonged high levels of glucocorticoids
What is Cushing’s disease?
Pituitary adenoma secreting excessive ACTH
Stimulates excessive cortisol from the adrenal glands
What are two common exogenous corticosteroids can cause Cushing’s syndrome?
Prednisolone
Dexamethasone
What features on inspection do you see with Cushing’s syndrome?
Moon face
Central obesity
Striae
Buffalo hump
Proximal limb muscle wasting
Hirsutism (in women)
Easy bruising and poor skin healing
Hyperpigmentation in Cushing’s disease (POMC)
What physiological effects are there in Cushing’s Syndrome?
Hypertension
Cardiac hypertrophy
T2DM
Dyslipidaemia
Osteoporosis
Anxiety
Depression
Insomnia
Psychosis
What are the causes of Cushing’s syndrome?
Cushing’s disease
Adrenal adenoma (secretes excess cortisol)
Paraneoplastic syndrome
Exogenous steroids
What is Paraneoplastic Cushing’s syndrome?
ACTH released from a tumour elsewhere from the pituitary gland
Small cell lung cancer most common
Ectopic ACTH stimulates excessive cortisol release
Why do you get hyperpigmentation with Cushing’s disease?
ACTH is produced from the cleavage of POMC
POMC produces ACTH and MSH
MSH causes increased melanin production causing hyperpigmentation
What is a dexamethasone suppression test used for?
Cushing’s syndrome diagnosis
What is a normal response to a dexamethasone suppression test?
Suppressed cortisol due to negative feedback
Reduced CRH from hypothalamus
Decreased ACTH from anterior pituitary
Low cortisol serum levels
What is a low-dose overnight dexamethasone suppression test?
Screening to exclude Cushing’s syndrome
Dexamethasone given at night and cortisol checked at 9 am next morning
Normal result causes reduced cortisol serum levels
What is a low-dose 48-hour dexamethasone suppression test?
Suspected Cushing’s syndrome
Dexamethasone taken every 6 hours 8 times starting at 9 am first day
Cortisol checked initially and at the end, failure to suppress indicates Cushing’s syndrome
What is a high-dose 48-hour test?
Determine cause in confirmed Cushing’s syndrome
Higher dose can suppress pituitary adenoma (Cushing’s disease) but not when it is caused by adrenal adenoma or ectopic ACTH
2mg per dose vs 0.5mg
Complete the table
What other investigations are used for Cushing’s syndrome?
FBC
U&Es (low potassium if adrenal adenoma is secreting aldosterone too)
MRI brain (pituitary adenoma)
CT chest (small cell lung cancer)
CT abdomen for adrenal tumours
