= Gonadotropin-releasing hormone
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= GnRH
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<Gonadotropin-releasing hormone> (<GnRH>) is a <peptide hormone> secreted by hypothalamic <neurons> that regulates release of <luteinizing hormone> and <follicle-stimulating hormone> from <gonadotrophs> in the <anterior pituitary>. The <hypophyseal portal system> carries this upstream signal directly to its pituitary target.
The releasing factor and the released products are separate <hormones>. That distinction was made experimentally by testing hypothalamic material for its ability to stimulate pituitary output. A 1971 report by <Andrew Schally> and collaborators described a purified releasing factor that stimulated both <luteinizing hormone> and <follicle-stimulating hormone>, helping establish a common hypothalamic input to the two responses.<Hypothalamic follicle-stimulating hormone (FSH) and luteinizing hormone (LH)-regulating hormone: structure, physiology, and clinical studies by Andrew Schally and others>[Abstract: a single purified hypothalamic releasing hormone stimulates both LH and FSH]{ref}
Timing is part of the signal. In the 1982 <sheep> study by <Iain J. Clarke> and <James T. Cummins>, <GnRH> pulses measured in portal <blood plasma> were synchronous with <LH> pulses measured downstream in peripheral <blood plasma>.<The temporal relationship between gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH) secretion in ovariectomized ewes by Iain J. Clarke and James T. Cummins>[Abstract: the two sampling locations and pulse synchrony]{ref} The <hypophyseal portal system> article describes that measurement geometry in more detail.
A time-averaged <concentration> therefore discards information about the pattern of <hormone> delivery. The experiment measured both the upstream signal and its pituitary output, linking a chemical identity to a physiological rhythm.
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