Dissociation of gonadal and adrenal androgens one year after etonogestrel implant insertion

Background Paired hormonal data spanning a full androgen panel before and during etonogestrel (ENG) implant use are scarce. We quantified within-subject hormonal change about one year after ENG implant insertion and tested whether it differed by menstrual bleeding phenotype.Methods In this paired cohort study, 200 women with an ENG 68 mg implant in situ for 10–14 months attended a single index visit. Pre-insertion hormone values, obtained routinely before insertion, were retrieved from records; current values were measured at the index visit in the same laboratory. Paired comparisons used the Wilcoxon signed-rank test, reporting Cohen’s dz and absolute change with 95% CIs; post-implant values were compared between bleeding phenotypes by ANCOVA adjusted for age, BMI, and parity, with multiple-testing correction.Results LH showed the largest decrease (−47.1%; dz = 1.84), followed by SHBG (−49.8%; dz = 1.42), total testosterone (−45.3%; dz = 1.24), and free testosterone (−46.0%; dz = 1.08). Oestradiol, AMH, and DHEA-S changed by ≤3% and, though significant, were clinically negligible (dz ≤ 0.60). Regular monthly bleeding fell from 95.5% to 45.0% (p < 0.001), with no frequent, prolonged, or heavy bleeding. After adjustment, no hormonal value differed by bleeding phenotype (all p ≥ 0.38).Conclusion One year after ENG implant insertion, deep LH suppression was accompanied by parallel reduction of gonadal androgens (total and free testosterone) and SHBG, whereas oestradiol, AMH, and adrenal DHEA-S were essentially unchanged, indicating a dissociation between suppressed gonadal and preserved adrenal androgens. The reduced-bleeding phenotype was not accompanied by differential hormonal change.