Cushing Syndrome and Adrenal Insufficiency

Cortisol helps maintain vascular tone, glucose availability during stress, immune regulation, and the normal circadian response to illness. Too much cortisol and too little cortisol produce almost opposite clinical pictures, but both can become life-threatening. Cushing syndrome is the clinical state of prolonged, inappropriate cortisol excess. Exogenous glucocorticoid therapy is the most common cause overall. For endogenous disease, an ACTH-secreting pituitary adenoma is the most common cause; this pituitary form is called Cushing disease. Ectopic ACTH production and cortisol-producing adrenal tumours account for most other endogenous cases. Sustained cortisol excess redistributes fat centrally while breaking down protein in muscle, skin, and bone. The resulting pattern is central adiposity, facial rounding, dorsocervical fat accumulation, thin skin, easy bruising, wide violaceous striae, poor wound healing, and proximal muscle weakness. A patient who needs their arms to rise from a chair or climb stairs has lost functional muscle mass, not simply fitness. Cortisol also raises glucose, increases vascular reactivity, and weakens bone, creating a cluster of hypertension, diabetes or impaired glucose tolerance, osteoporosis, and fragility fractures. Primary adrenal insufficiency, or Addison disease, occurs...