The LH/FSH ratio has little use in diagnosing polycystic ovarian syndrome

Background: The luteinizing hormone/follicle stimulating hormone (LH/FSH) ratio is often requested to help diagnose polycystic ovarian syndrome (PCOS) despite a recent consensus recommending against its use. This study aimed to compare the variability of the LH/FSH ratio in PCOS with that of normal menstruating women over a full cycle in order to establish the diagnostic utility, or otherwise, of the test. Methods: Twelve women with PCOS and 11 matched controls had blood collected at four-day intervals on 10 consecutive occasions over a complete menstrual cycle. Results: The median LH/FSH ratio for individual subjects did not differ significantly between the PCOS and the non-affected group (1.6 versus 1.2, P=0.14). Only 7.6% of samples from PCOS patients had an LH/FSH ratio above three, compared with 15.6% of samples from normal subjects. Conclusion: This study confirms that measurement of the LH/FSH ratio is of limited use in the diagnosis of PCOS.