IGF1 and Familial prostate cancer: 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.