Phenotypes and clinical laboratory data for polycystic ovary syndrome cases: A nationwide survey in Japan.

Aim: Describe the current phenotypes and clinical laboratory data regarding polycystic ovary syndrome (PCOS) in Japan, taking into account ethnic differences and obesity status.

Methods: Data for 986 PCOS cases and 965 control cases were collected using a nationwide survey in Japan. Obese/overweight (body mass index [BMI] ≥25 kg/m²) and non-obese/overweight (BMI <25 kg/m²) cases were compared.

Results: Japanese PCOS cases predominantly involved non-obese/overweight patients, accounting for 75% of all cases. Among non-obese/overweight PCOS cases, the incidence of both amenorrhea and clinical/biochemical hyperandrogenism was significantly lower than in obese/overweight PCOS cases, whereas the rate of elevated serum luteinizing hormone (LH) level was significantly higher. Even though the incidence of hirsutism in Japan is only 13.5%, the detection rate for hyperandrogenism increased by as much as 30.4% when hirsutism was added to the Japan Society of Obstetrics and Gynecology (JSOG) criteria for the diagnosis of hyperandrogenism in addition to elevated serum total testosterone level. When evaluated based on timing of blood sampling, the LH level and LH/follicle-stimulating hormone ratio determined at the initial consultation involving a chief complaint of irregular menstrual cycle (after confirming the absence of follicles measuring ≥1 cm in diameter) were significantly higher than on days 2-3 or 4-6 of the menstrual cycle.

Conclusions: Ethnic differences, including obesity status, affected the phenotype and clinical laboratory data of Japanese PCOS patients, such as the incidence rates of clinical/biochemical hyperandrogenism and the rate of elevated basal LH level. Adding hirsutism to the JSOG 2024 criteria would enhance the accuracy of PCOS diagnosis and enhance consistency with the Rotterdam 2003 criteria. Measuring basal LH level is useful for assessing the endocrinologic characteristics of Japanese PCOS cases, as well as lean Asian PCOS cases, but the timing of blood sampling can affect the result.