When Renold et al1 minted the term "insulin-like activity" (ILA) to designate their rat epididymal fat pad bioassay for insulin, they cautioned against a possible assumption that measured "insulin-like activity" is, in fact, insulin. An editorial in the New England Journal of Medicine2 finds that this cautionary advice often goes unheeded. There exists a "seductive tendency" to talk ILA, but to think insulin. Seduced by this tendency, we are apt to overlook important differences in antigenic properties and metabolic effects of the two entities. Beguiled by the illusory link to insulin implied in "insulin-like," we tend to forget that insulin is not the latter's sole component. Other substances, possibly unrelated to insulin, also contribute to ILA. The term "insulinlike" does not serve the cause of clarity.
Nor, for that matter, does the more recent "insulinoid"3—a hypothetical cause of hypoglycemia in some relatively rare, slow growing, mesenchymal
A LABORATORY MODALITY. JAMA. 1966;198(1):77-78. doi:10.1001/jama.1966.03110140127038