I think the term you are looking for is an "appeal to nature" which differs from the naturalistic fallacy. My comment was not appealing to nature, in that it made no judgement - good OR bad - in defining the synthesis and self-infusion of hormones as unnatural. It just is unnatural. By definition. In contrast with the OP's comment, I believe that's something we should all be able to accept without strife.

While it's true that everything we do is literally a part of nature (nature being the world around us), it makes sense to have a word to define biological substances or events that wouldn't otherwise occur without human intervention. E.g. artificial colors, artificial flavoring.