Whilst our literature search terms ‘intracrine and endometriosis’ only identified five papers on PUBMED it is notable that the alternative search ‘aromatase and endometriosis’ identified more than 300, reflecting widespread interest in the role of local (intracrine) biosynthesis in the aetiology of this complex disorder and the potential that this might provide a novel therapeutic opportunity [68]. The gene discussed is CYP19A1; the disease is endometriosis.