人类下丘脑和垂体前叶促肾上腺皮质激素（ACTH）与生长激素（GH）释放的正常生理学

Normal Physiology of ACTH and GH Release in the Hypothalamus and Anterior Pituitary in Man

作者信息

Lim Chung Thong, Khoo Bernard

机构信息

Endocrinology, Queen Mary University of London, UK

Division of Medicine, University College London, UK

Abstract

This chapter summarizes the intimate relationship between the hypothalamus and the anterior pituitary with respect to the secretion of ACTH and GH from the physiological viewpoint. Other chapters in Endotext cover the hormones prolactin, LH, FSH, TSH and the posterior pituitary. Adrenocorticotropic hormone (ACTH) and growth hormone (GH) are both peptide hormones secreted from the anterior pituitary. ACTH is derived from cleavage of the precursor hormone pro-opiomelanocortin (POMC) by prohormone convertase enzymes. Classically, it activates the production and release of cortisol from the zona fasciculata of the adrenal cortex via the melanocortin receptor MC2R. The major hypophysiotropic factor controlling ACTH expression and secretion is corticotropin-releasing hormone (CRH), in conjunction with arginine vasopressin (AVP). Key physiological features of the hypothalamo-pituitary-adrenal (HPA) axis are discussed, including the ultradian pulsatility of CRH, AVP and ACTH secretion, the circadian pattern of secretion, the negative feedback of cortisol on the HPA axis, the stress response, and the effects of aging and gender. GH is secreted mainly by somatotrophs in the anterior pituitary, but it is also expressed in other parts of the brain. Similarly, to ACTH, the release of GH is pulsatile with diurnal variation, under a negative feedback auto-regulatory loop, and can be affected by various factors. Activities that affect secretion of GH include sleep and exercise, and physical stresses such as fasting and hypoglycemia, hyperglycemia, hypovolemic shock, and surgery. GH secretion demonstrates differences between the sexes, with male ‘pulsatile’ secretion versus female ‘continuous’ secretion. In addition, the level of secretion also declines with age, a phenomenon termed the ‘somatopause’. All these are discussed in detail in this chapter. For complete coverage of all related areas of Endocrinology, please visit our on-line FREE web-text, WWW.ENDOTEXT.ORG.

摘要

本章从生理学角度总结下丘脑与腺垂体之间关于促肾上腺皮质激素（ACTH）和生长激素（GH）分泌的密切关系。Endotext中的其他章节涵盖了催乳素、促黄体生成素（LH）、促卵泡生成素（FSH）、促甲状腺激素（TSH）以及神经垂体。促肾上腺皮质激素（ACTH）和生长激素（GH）均为腺垂体分泌的肽类激素。ACTH由前体激素阿黑皮素原（POMC）经激素原转化酶裂解产生。传统上，它通过黑皮质素受体MC2R激活肾上腺皮质束状带中皮质醇的产生和释放。控制ACTH表达和分泌的主要促垂体因子是促肾上腺皮质激素释放激素（CRH），以及精氨酸加压素（AVP）。讨论了下丘脑-垂体-肾上腺（HPA）轴的关键生理特征，包括CRH、AVP和ACTH分泌的超日脉冲性、昼夜分泌模式、皮质醇对HPA轴的负反馈、应激反应以及衰老和性别的影响。GH主要由腺垂体中的生长激素细胞分泌，但也在大脑的其他部位表达。同样，与ACTH类似，GH的释放呈脉冲式且有昼夜变化，处于负反馈自动调节环路之下，并可受多种因素影响。影响GH分泌的活动包括睡眠和运动，以及禁食、低血糖、高血糖、低血容量性休克和手术等身体应激。GH分泌在性别上存在差异，男性为“脉冲式”分泌，而女性为“持续性”分泌。此外，分泌水平也会随着年龄增长而下降，这一现象称为“生长激素缺乏症”。本章将对所有这些内容进行详细讨论。欲全面了解内分泌学的所有相关领域，请访问我们的在线免费网络文本，WWW.ENDOTEXT.ORG。