SUN-208 The Intra-Individual Variability of 11-Ketotestosterone and 11β-Hydroxyandrostenedione

Background Emerging evidence has suggested the 11-oxygenated steroids may be important in the diagnosis and monitoring of hyperandrogenism. Two in particular, 11-ketotestosterone (11KT) and 11β-hydroxyandrostenedione (11OHA4) have been implicated in polycystic ovary syndrome, congenital adrenal hyperplasia, precocious puberty and castration resistant prostate cancer. Despite the interest in these analytes, some of their more fundamental properties have yet to be determined. At present, no data is available that quantifies the biological variation of 11KT and 11OHA4 within individuals over time, this may be important as we look to establish normative reference ranges for these potentially useful analytes. Objective Here we sought to define the intra-individual variability of 11KT and 11OHA4 in serum using LC-MS/MS. Method Blood was collected from 18 healthy volunteers (8 males, 10 females) on the same day each week over a 10 week period using standard venepuncture technique. After collection, the samples were centrifuged within 1 hour, aliquoted and stored at -20°C (-4°F) prior to analysis. All samples from individual volunteers were analysed by LC-MS/MS in triplicate within the same batch so as to limit analytical variability. Results The mean analytical coefficient of variation (CV%) for the triplicate analysis was 3.2% for 11KT and 3.7% for 11OHA4. No significant difference was observed between the variability of 11KT concentrations in the male and female cohorts; total intra-individual variation for 11KT was 18.0%. Concentrations of 11OHA4 were more variable in the male cohort when compared to the female cohort. This was reflected by differences in their respective intra-individual variations of 32.5% vs 24.8%. Summary Intra-individual variation is an important consideration when interpreting patient results. Concentrations of 11KT were tightly regulated in both the male and female cohorts with no clear demarcation between the two groups. Although concentrations of 11OHA4 were prone to greater variation over the 10 week period, considerable overlap was observed between the male and female subjects. Our data suggests that 11KT and 11OHA4 concentrations are not significantly affected by the menstrual cycle.