159 Leptin, hunger and fat 5 Since leptin values are highly variable between patients and are known to depend on sex, body mass index (BMI) and puberty stage, they are presented as SDS using previously described normative values taking these factors into account.25 Since we did not document the puberty stage of our cohort, for this study, puberty stage was approximated per patient using the median age of reaching the stages of secondary sex characteristics in the general Dutch population, using reference values of the 1997 Dutch Growth Study.26 Statistical analyses Patient characteristics and measurement results were reported as mean along with standard deviation (SD) or median with interquartile range (IQR) depending on the distribution of the variables. Delta values were calculated by subtracting T1 values from T2 values. The changes in leptin SDS, fat mass, hunger scores, fatigue and sleep after five days of dexamethasone (T2 versus T1) were assessed using paired tests: a Paired T-test in case of normally distributed measures or a Wilcoxon Signed Rank test in case of skewed distribution. To explore correlations between delta leptin and delta fat mass, hunger scores, fatigue and sleep, Spearman correlation coefficients were estimated together with the 95%-confidence intervals (95%-CI). A correlation between 0.0 and 0.3 is negligible, between 0.3 and 0.5 low, between 0.5 and 0.7 moderate, between 0.7 and 0.9 high and >0.9 very high.27 To explore possible contributing factors (patient demographics and treatment characteristics) for a high leptin value on T1, univariable logistic regression models were estimated: a cutoff of SDS >1,5 was used to define high leptin values at T1. Furthermore, linear regression models were estimated to explore potential influencing factors for change in leptin levels after five days of dexamethasone (delta leptin), with correction for T1 leptin values. All analyses were performed using IBM SPSS Statistics version 26.0.
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