Cushing's Syndrome
The clinical condition resulting from prolonged excess cortisol, regardless of cause (pituitary tumour, adrenal tumour, exogenous steroids, or ectopic ACTH). Symptoms include central obesity, moon face, muscle weakness, skin fragility, and metabolic complications.
Technical Context
Cushing's syndrome (CS) — the clinical state of chronic cortisol excess regardless of cause. Causes: exogenous (iatrogenic — most common overall, from chronic glucocorticoid therapy), ACTH-dependent endogenous (Cushing's disease ~70%, ectopic ACTH ~10%), and ACTH-independent endogenous (adrenal adenoma ~15%, adrenal carcinoma ~5%). Clinical features: central obesity with proximal muscle wasting, moon face, buffalo hump, purple striae (>1cm wide), skin fragility/easy bruising, hypertension, glucose intolerance/diabetes, osteoporosis, emotional lability/depression, and immunosuppression. Screening: multiple positive screening tests required (UFC, LDSST, midnight salivary cortisol). Differential diagnosis between aetiologies uses: plasma ACTH level, high-dose dexamethasone suppression test, CRH stimulation test, and IPSS (inferior petrosal sinus sampling). Medical therapy targets vary by cause — pasireotide for pituitary, metyrapone/ketoconazole for any cause (adrenal steroidogenesis inhibition).