Kortisolin

Kortisolin, also known as cortisol, is a steroid hormone produced mainly by the adrenal cortex. As the principal glucocorticoid in humans, it helps regulate metabolism, the immune response, and the body’s adaptation to stress.

Production and regulation: Kortisolin secretion is controlled by the hypothalamic–pituitary–adrenal (HPA) axis. Corticotropin-releasing hormone (CRH) from the hypothalamus stimulates adrenocorticotropic hormone (ACTH) release from the pituitary, which in turn promotes cortisol synthesis in the adrenal cortex. Levels exhibit a pronounced circadian rhythm, peaking in the early morning and declining through the day, with rapid increases in response to physical or psychological stress.

Mechanism and actions: Kortisolin acts by binding to glucocorticoid receptors in many tissues, altering gene transcription. It also interacts with mineralocorticoid receptors in certain contexts. It promotes gluconeogenesis, protein catabolism, and lipolysis; it reduces immune and inflammatory responses; and it helps regulate blood pressure and vascular responsiveness. Local inactivation or activation is mediated by 11β-hydroxysteroid dehydrogenase enzymes in tissues.

Clinical relevance: Abnormally high cortisol production causes Cushing’s syndrome; insufficient production leads to Addison’s disease. Diagnosis relies on morning serum cortisol, ACTH levels, dexamethasone suppression tests, 24-hour urinary free cortisol, and salivary cortisol as a noninvasive measure of free hormone.

Therapeutic and practical notes: Synthetic glucocorticoids (e.g., dexamethasone, prednisone) imitate kortisolin’s effects and are used to treat inflammatory and autoimmune conditions. Long-term use can suppress the HPA axis and cause side effects; withdrawal requires careful tapering.