How important is the LH: FSH ratio?
An LH level higher than the FSH level suggests the existence of PCOS. However the ratio between the two has only a suggestive value and not a diagnostic value by itself. Thus is no longer used for diagnosis. In a sub fertile patient, however, it does help in planning the treatment and evaluating the response to it.
The emphasis doctors place on the ratio of luteinizing hormone (LH) to follicle stimulating hormone (FSH) varies. Most pre-menopausal women have a ratio close to1:1. In PCOS, the LH level may rise above the FSH, sometimes significantly. Any case where the LH is higher may be suggestive of PCOS and further investigation may be warranted. Some doctors say that an LH:FSH greater than 2:1 or 3:1 indicates PCOS.