The lack of association between BMI and E2 levels in the present study may be due to the lower proportion of patients who were on AI compared to SOFT-EST, lessening the potential impacts of obesity, and consequent increased total body aromatization, on the efficacy of AIs to fully inhibit the aromatase enzyme and suppress estrogen production28. Here, CYP19A1 is linked to obesity due to melanocortin 4 receptor deficiency.