The human endocrine system consists of glands that secrete hormones to regulate body functions. Key glands include the brain, pituitary, thyroid, adrenal glands, kidneys, and pancreas. The adrenal glands, located above the kidneys, have two main parts: the outer cortex and inner medulla. The adrenal cortex produces two important hormone categories: mineralocorticoids like aldosterone, which regulate salt and water balance, and glucocorticoids like cortisol, which control metabolism and stress responses.
Aldosterone is the primary mineralocorticoid produced by the adrenal cortex. It works through the renin-angiotensin-aldosterone system, or RAAS. When blood pressure drops, the kidneys release renin, which converts angiotensinogen to angiotensin, ultimately stimulating aldosterone release. Aldosterone acts on the kidneys' distal tubules and collecting ducts to increase sodium retention and potassium excretion. This process increases blood volume and blood pressure, maintaining fluid homeostasis. Aldosterone also affects the colon and salivary glands to conserve sodium.
Cortisol is the primary glucocorticoid hormone, essential for glucose metabolism and stress responses. It operates through the hypothalamic-pituitary-adrenal axis, or HPA axis. When stress occurs, the hypothalamus releases CRH, which stimulates the pituitary to release ACTH, which then triggers cortisol release from the adrenal cortex. Cortisol targets multiple tissues: it stimulates glucose production in the liver through gluconeogenesis, promotes protein breakdown in muscles, and enhances lipolysis in adipose tissue. This provides energy during stress or fasting states. Cortisol also provides negative feedback to regulate its own production.
Cortisol has complex metabolic effects across multiple tissues. In the liver, cortisol stimulates gluconeogenesis, the production of glucose from non-carbohydrate sources, and glycogenolysis, the breakdown of glycogen to glucose. In muscle tissue, cortisol promotes protein catabolism, breaking down muscle proteins into amino acids that can be used for glucose production. In adipose tissue, cortisol enhances lipolysis, breaking down stored fats into fatty acids and glycerol. These coordinated actions increase blood glucose levels, providing energy during stress, fasting, or exercise. This is why cortisol is often called the stress hormone.
盐皮质激素和糖皮质激素是人体内分泌系统中的两类重要激素，它们都由肾上腺皮质分泌。盐皮质激素主要调节体内的水盐平衡，而糖皮质激素则主要调节糖代谢和应激反应。这两类激素在维持人体内环境稳定方面发挥着至关重要的作用。
醛固酮是最重要的盐皮质激素，主要在肾小管和集合管发挥作用。它促进钠离子的重吸收，同时促进钾离子的分泌。通过调节钠钾平衡，醛固酮能够维持血压稳定和体液容量平衡。醛固酮的分泌主要受肾素-血管紧张素系统调节，当血压下降或血钾升高时，醛固酮分泌增加。
皮质醇是最重要的糖皮质激素，具有多种生理功能。它主要促进糖异生，增加血糖浓度，同时促进蛋白质和脂肪的分解为糖异生提供原料。皮质醇还具有强大的抗炎作用，能够抑制免疫反应。它的分泌受下丘脑-垂体-肾上腺轴调节，具有明显的昼夜节律，在应激状态下分泌显著增加。
盐皮质激素和糖皮质激素的分泌受到严格的调节。糖皮质激素主要通过下丘脑-垂体-肾上腺轴调节：下丘脑分泌促肾上腺皮质激素释放激素，刺激垂体分泌促肾上腺皮质激素，进而刺激肾上腺皮质分泌皮质醇。皮质醇通过负反馈机制抑制上级激素的分泌。而醛固酮的分泌主要受肾素-血管紧张素系统调节，同时也受到昼夜节律和应激状态的影响。
盐皮质激素和糖皮质激素的异常会导致多种疾病。盐皮质激素过多可引起原发性醛固酮增多症，表现为高血压和低钾血症。糖皮质激素过多会导致库欣综合征，患者出现高血糖、高血压、向心性肥胖等症状。而两种激素都不足时会发生阿狄森病，患者表现为低血糖、低血压、严重乏力等。在临床上，这些激素广泛用于激素替代疗法和抗炎治疗，但需要严格控制剂量以避免副作用。