Alternative explanations for the observed association of IGF‐axis peptides with prostate cancer include: reverse causality, because tumours may promote an endocrine response7; confounding by dietary,8 nutritional9 and lifestyle10 factors; measurement error,11 as single serum measurements may inadequately reflect long‐term exposure; or detection bias,11 occurring, for example, if IGF‐I causes symptomatic benign prostatic hyperplasia (BPH) that results in the serendipitous finding of latent cancer on diagnostic biopsy. This evidence concerns the gene IGF1 and prostate cancer.