LH as a diagnostic criterion for polycystic ovary syndrome in patients with WHO II oligo/amenorrhoea

Elevated LH is common in polycystic ovary syndrome (PCOS), but is not part of the diagnostic criteria. LH concentrations are usually assessed in the early ‘follicular’ phase when it is suppressed, and therefore the prevalence is underestimated. In this study, LH is measured during the ‘specific oligomenorrhoeic phase’, when LH is least suppressed, and its importance as a diagnostic tool for PCOS is evaluated. Patients presenting with oligo- or amenorrhoea between 2002 and 2006 were selected, with the exclusion of women with WHO III oligoamenorrhoea, hyperprolactinaemia or with wrongly timed endocrine measurements. A total of 252 patients were included (198 oligo/amenorrhoeic PCOS patients and 54 oligo/amenorrhoeic controls). Mean LH concentrations were higher in PCOS patients than in controls (11.0 versus 4.1 IU/l, P < 0.001). The receiver operating characteristics (ROC) curve showed an optimal cut-off for LH of ≥6.5 IU/l, resulting in a sensitivity of 84%, specificity of 78% and a likelihood ratio of 3.8, and elevated LH concentrations predicted PCOS accurately in 93%. In conclusion, elevated LH concentrations are found in a large majority of PCOS patients when measured at the appropriate time, and could be used as an additional diagnostic test to differentiate between oligo/amenorrhoeic PCOS patients and other causes of oligo- or anovulation.