The PCOS Phenotype in Unselected Populations study: ethnic variation in population-based normative cut-offs for defining hirsutism.

Objective: Hirsutism, a diagnostic feature of polycystic ovary syndrome (PCOS), is often defined using arbitrary percentile cutoffs, rather than normative cutoffs from population-based data. We aimed to define normative cutoffs for hirsutism in diverse populations.

Design: Unselected population-based cluster analysis of individual participant data (IPD).

Methods: The PCOS Phenotype in Unselected Populations (P-PUP) study IPD asset of community-based studies, underwent k-means cluster analysis, of directly assessed hirsutism, using the modified Ferriman-Gallwey (mFG) visual scale. The primary outcome was ethnicity-specific normative cutoffs for the mFG score. Medians and cutoffs were compared across ethnic groups.

Results: We included 9829 unselected, medically unbiased participants, aged 18-45 years from 12 studies conducted across 8 countries including China, Iran, Italy, Nigeria, Russia, South Korea, Turkey, and the United States. The mFG cutoff scores for hirsutism on cluster analysis varied across ethnicities, ranging from 4 to 8. White Iranians had the highest cutoff score of 8, followed by White Italians and Black Africans of 7. Asian Han Chinese, White Russian, Turkish, and Black Americans shared a cutoff of 5; White Americans, Asian Koreans, Asian Russians, and Mixed Russians shared a cutoff of 4. Comparing medians and mFG cutoffs across ethnicities confirmed the same differences.

Conclusion: This study confirms the 2023 International PCOS Guidelines recommendations defining hirsutism as an mFG score between 4 and 6 for the majority of populations studied, with few exceptions. However, we also highlight ethnic variation in mFG cutoff scores, suggesting that clinicians consider ethnicity in optimal diagnosis and personalized interventions.