The stomach talks with the pituitary

[...]with increasing plasma levels of IGF-I and/or GH, the release of GH is inhibited. 1 In 1984 a synthetic hexapeptide, containing two D-amino acid residues, was demonstrated to cause the release of GH. 2 Subsequently, it was shown that this peptide and other non-peptidergic GH secretagogues (GHSs) did not act via any of the known cell membrane receptors controlling GH secretion. [...]this research field was in the somewhat peculiar situation of having a well characterised cell membrane receptor as well as knowing in some detail the intracellular events occurring on stimulation of the receptor without knowledge of how and when it was physiologically stimulated.