Cortisol
The primary glucocorticoid hormone produced by the adrenal cortex in response to ACTH stimulation. Cortisol regulates metabolism, immune function, and the stress response. Excess cortisol (Cushing's syndrome) can result from ACTH-secreting pituitary tumours treated with pasireotide.
Technical Context
Cortisol is synthesised from cholesterol in the adrenal zona fasciculata under ACTH control. It acts through the glucocorticoid receptor (GR, a nuclear receptor), affecting gene transcription in virtually all tissues. Cortisol's physiological actions include: glucose mobilisation (gluconeogenesis, glycogenolysis), protein catabolism, fat redistribution, immunosuppression, and anti-inflammatory effects. In Cushing's disease, an ACTH-secreting pituitary adenoma drives excessive cortisol production. Cortisol measurement (24-hour urinary free cortisol, midnight salivary cortisol, low-dose dexamethasone suppression test) is used to diagnose Cushing's syndrome. The ACTH stimulation test (cosyntropin) assesses the adrenal gland's ability to produce cortisol in suspected adrenal insufficiency.