Amyloid is a fibrillar protein conformation often associated with disease, yet it can also play essential roles in biology. Peptide hormones are key regulators of metabolism and utilise a functional amyloid state to concentrate and store peptides in a stable, inert conformation until external signals trigger release into receptor-active hormone monomers. Despite the fundamental biological importance of peptide hormones, their amyloid structure and high-resolution insights into their mechanism of assembly/disassembly remain poorly understood. To gain an understanding of the structure-formation relationship of peptide hormone amyloid, the human tachykinin peptides Substance P, Neurokinin A, and Neurokinin B were characterised as these peptides have previously been observed to form amyloid with non-canonical features when examined by spectroscopic techniques. We used biophysical and structural methods including circular dichroism spectroscopy, as well as negative-stain and cryo-electron microscopy. Five high-resolution tachykinin peptide amyloid structures were solved, with NKA and NKB forming two polymorphs each, and SP presenting with a single fibril type. These structures reveal the first nanotubular amyloids from proteins of eukaryotic origin and indicate the existence of a new structural class of amyloid fibril. Furthermore, the structure of these nanotubes is unique compared to other nanotubular peptide aggregates of largely synthetic origin, presenting with amyloid defining features and small inner pores relative to the thickness of the fibril. The organisation of the peptides within the fibril compared to their receptor bound conformations suggest that the amyloid state prepares hormone monomers for rapid release in a conformation primed for tachykinin receptor activation. These findings mark a major step toward structurally defining the peptide hormone functional amyloidome.