This abnormal secretion of ovarian A4 is an intrinsic property of PCOS theca cells [26] and, contrary to the conventional view, this then leads to excess LH, with the expected excess E2-related supression of pituitary LH release being opposed by excess A4 and this is what then drives the increase in LH secretion in this phenotype. Here, PLOD1 is linked to polycystic ovary syndrome.