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Andrew Schally studied how the hypothalamus controls secretion by the pituitary gland through small peptides. His work helped establish a chemical connection between brain activity and the release of hormones, and he shared the 1977 Nobel Prize in Physiology or Medicine for discoveries concerning brain peptide hormone production. He worked at Tulane and the Veterans Affairs hospital in New Orleans for more than four decades.^[ref]

One important experimental question was whether separate hypothalamic signals were needed for the two gonadotropins, luteinizing hormone and follicle-stimulating hormone. Schally and colleagues' 1971 report described a purified hypothalamic factor that stimulated both. This connected a chemically characterized signal to two measured pituitary gland responses and helped establish the role of gonadotropin-releasing hormone.^[ref]

Portrait attributed to NASA in the Wikimedia Commons file record.

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.^[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.^[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.