(135) Variability in FSH Levels Limits the Reliability of Hormone Testing for POI Diagnosis

Abstract Introduction Serum follicle-stimulating hormone (FSH) is recommended to make the diagnosis of premature ovarian insufficiency (POI). Current NICE guidance (NG23), IMS, ESHRE, BMS and TMC guidelines advise FSH testing to confirm POI in symptomatic women aged under 40. However, there is considerable variation in the diagnostic thresholds for FSH across these guidelines, with cut-offs ranging from 25 to 40 IU/L. This wide range highlights the lack of consensus and makes clinical decision-making challenging, as there is no universally accepted value for defining POI. Furthermore, there is no good quality evidence to support these recommendations, and many women with normal or low FSH levels are being refused hormone treatments despite being symptomatic. Hormonal secretion in women with POI can be highly variable, raising concerns that single-timepoint hormone values may not be a reliable method for making a diagnosis of POI in some women. Objective To quantify levels of serum FSH among women under 40 assessed for suspected POI, and to evaluate whether the level of FSH supports its use as reliable diagnostic indicators in this age group as outlined in national and international menopause guidelines. Methods This retrospective cohort study included women attending Newson Clinic with baseline hormone testing performed. Serum FSH (mIU/mL) concentrations were analysed by Nationwide Pathology (Leicestershire, UK) using the Atelica IM Enhanced Estradiol (eE2) assay, according to manufacturer instructions. Participants were grouped by age: 40 years (POI group, n = 48). Results Serum hormone levels demonstrated wide inter-individual variability. FSH ranged from 1.91-93.65 mIU/mL (median 6.43, IQR 4.38-8.06), corresponding to approximately 49-fold difference across individuals. These results demonstrate marked FSH variability in young women. Conclusions These findings indicate that single-timepoint FSH measurement provides limited diagnostic reliability for POI in women under 40. This challenges current guidelines for POI and suggests that the authors of the menopause guidelines should reconsider their recommendations. This also has particular relevance given the growing use of commercial self-testing services offering single-result FSH hormone panels. Disclosure No.