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Principles of hormone action 

Principles of hormone action

Chapter:
Principles of hormone action
Author(s):

Mark Gurnell

, Jacky Burrin

, and V. Krishna Chatterjee

DOI:
10.1093/med/9780199204854.003.1301_update_001

August 28, 2014: This chapter has been re-evaluated and remains up-to-date. No changes have been necessary.

Update:

Minor updates made to table of genetic defects in membrane receptors or signalling and endocrine disorders.

Updated on 30 Nov 2011. The previous version of this content can be found here.
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date: 26 March 2017

Hormones, produced by glands or cells, are messengers which act locally or at a distance to coordinate the function of cells and organs. Types of hormone include (1) peptides (e.g hypothalamic releasing factors) and proteins (e.g. insulin, growth hormone)—these generally interact with membrane receptors located on the cell surface, causing activation of downstream signalling pathways leading to alteration in gene transcription or modulation of biochemical pathways to effect a physiological response; (2) steroids (e.g. cortisol, progesterone, testosterone, oestradiol) and other lipophilic substances (e.g. vitamin D, retinoic acid, thyroid hormone)—these act by crossing the plasma membrane to interact with intracellular receptors, with hormone action via nuclear receptors altering cellular gene expression directly.

Hormone synthesis, processing and secretion—production of hormones can be regulated at many levels, including (1) gene transcription; (2) mRNA processing; (3) post-translational modification. Some hormones are not significantly concentrated within cells and are released via Golgi-derived transport vesicles that fuse with the plasma membrane (a ‘constitutive’ pathway of secretion). By contrast, many endocrine cells contain an additional ‘regulated’ secretory pathway, which allows the export of high concentrations of hormone stored in cytoplasmic vesicles. Many hormones are released in a rhythmic or pulsatile manner.

Control of hormone production—the classical mechanism by which hormone-producing glands are controlled is by negative feedback, e.g. tri-iodothyronine (T3) inhibits production of thyrotropin releasing hormone and thyroid stimulating hormone.

Physiological roles of hormones—these are enormously varied and include (1) control of growth and differentiation; (2) maintenance of homeostasis—energy balance, metabolic pathways; fluid, electrolyte and calcium balance; control of blood pressure; and (3) regulation of reproduction.

Clinical features of endocrine disorders—these comprise conditions of either hormone excess or hormone deficiency or hormone resistance, with germ-line or somatic defects in genes mediating hormone synthesis or action causing inherited syndromes or acquired endocrine cellular dysfunction.

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