The terms 'autacoid', 'hormone' and 'chalone' and how they have shifted with time.

The increase of knowledge in a particular field (endocrinology) can be understood if one follows how certain key concepts were constructed and transformed over time. To explore such construction and transformation (shifts in meaning), we studied the use of the concepts 'autacoid' and 'chalone' in a period of one century (1916-2016), since the introduction of these concepts by the British professor of physiology Sir Sharpey-Schäfer. We could identify that the use of 'autacoid' shifted from a very broad category encompassing both stimulating and inhibiting hormones, in the period 1916-1960, to a much more specific use of the term for locally produced bioactive molecules, from the 1960s onwards. Histamine was the first compound seen as an 'autacoid', followed by prostaglandins, ATP, ADP and bradykinin, and from 1993 onwards, compounds such as 'palmitoylethanolamide' were also classified as 'autacoids'. For 'chalone', a comparable shift was noticed around the 1960s, when the concept suddenly changed from the category of inhibiting hormones into a substance that is produced within a tissue, inhibiting mitosis of the cells of that tissue. For both concept shifts, we could not find any argument. Around 1980, authors started to relate autacoids to various promising indications in the field of inflammation and immune modulation. The Nobel laureate Rita Levi-Montalcini gave an extra dimension to the concept autacoid in 1993, and introduced a new class of compounds modulating mast cells, the ALIAmides (from Autacoid Local Inflammation Antagonist), of which palmitoylethanolamide was the prototype. Our exploration demonstrates that biomedical concepts can be constructed and defined differently as time goes by, while concept transformations seem to emerge without arguments.