The facts of the matter: What is a hormone?

[...]in most cases these experiments were conducted not by us, but by labs with whom we had shared the Ocn-/- or Esp-/- or other relevant mutant mice and who were world experts in the particular assays being conducted. To name just a very small portion, euglycemic clamps were done in the laboratory of Jason Kim, islet perifusion in the lab of Klaus Kaestner, indirect calorimetry in the lab of Jeffrey Pessin, conditional fear conditioning in the lab of Rene Hen, electron micrographs of testes in the one of Louis Hermo, whole cell electrophysiology in the lab of Xiao-Bing Gao, and in vivo nerve fiber recordings in the lab of Kamal Rahmouni. Thirteen years later, even if it was painful at the time, I take this opportunity to thank each and every reviewer for having made this work what it is. Since the initial publication proposing that osteocalcin is a hormone there have been hundreds of publications confirming that osteocalcin behaves as a hormone that signals through two specific receptors that were notably identified by two competing groups and that elicits particular physiological responses in mice and humans. What is rewarding as an endocrinologist is to see that a large portion of this body of work was done as it should be, through gain-of-function experiments, and part of it in human cells or patients [9,39,51,52,56–61].