Whilst these studies reported a decrease in plasma INSL5 following weight loss post bariatric surgery (23) and elevated serum levels in patients with polycystic ovarian syndrome (24), the reported INSL5 concentrations were several orders of magnitude higher than typical levels of the co-secreted hormones GLP-1 and PYY, raising questions about assay reliability. Here, INSL5 is linked to polycystic ovary syndrome.