ABSTRACT Introduction Gender-affirming bilateral orchiectomy (GABO) can be offered to patients in 3 ways: as a stand-alone procedure, as a separate pre-vaginoplasty surgery, or, during vaginoplasty surgery. Because testicles are the predominant source of endogenous testosterone, GABO affords patients cessation of anti-androgen therapy, usually coupled with a decrease in their estrogen dose. Hormone therapy has known side effects, including cardiovascular and urinary effects, that have been suggested to be dose-dependent. In this study we measure postoperative decrease in gender-affirming hormone therapy after pre-vaginoplasty orchiectomy. Objective To evaluate postoperative changes in gender-affirming hormone therapy dosages for transgender women that have undergone pre-vaginoplasty orchiectomy. Methods We performed a retrospective review of all trans-feminine patients who underwent pre-vaginoplasty gender-affirming GABO. We recorded surgical data, demographic data, and changes (preoperative vs. postoperative) in gender-affirming hormone regimens, dosages. Hormone regimens were managed by patients’ outpatient endocrinologists. Gender dysphoria changes were measured on a 10-point Likert scale. Results 89 patients underwent pre-vaginoplasty GABO from 4/2017 – 12/2020. Mean age was 35.9Y and mean BMI was 27.4. GABO was performed via a single 2-3 cm. midline scrotal incision immediately posterior to the penoscrotal junction. Pre-operative estrogen data was available for 80/89 patients, and preoperative vs postoperative PO estrogen comparative data (where estrogen was the same formulation) was available for 41/89 patients. Pre-orchiectomy: 86 patients (96.6%) patients were taking estradiol (Mean PO dose: 28.5 mg/day; Route: PO 56.9%; IM 38.4%; transdermal 2.3%, SL 1.2% of patients, implant 1.2%), 69 (80.2%) patients were on Spironolactone (mean dose 140.8 mg QD), and 24(27.9%) patients were on progesterone (mean dose 104.6 mg QD). Post-orchiectomy, all (100%) patients taking spironolactone pre-op were able to discontinue it. Of patients taking progesterone, 79.1% patients were able to discontinue it post-orchiectomy. For patients on Estradiol, 40.6% of patients transitioned to a lower dosage (*mean: 45 % of the pre-op dose). Also, postoperatively, (87/89) of patients endorsed decreased genital-associated gender dysphoria (mean: 30% decrease). All patients who tucked (100%) reported relief of tucking related discomfort. All patients reported significant satisfaction with surgery and reduced postoperative hormone usage. Conclusions This is the first study to characterize dose changes in hormone therapy after gender-affirming orchiectomy. After orchiectomy, patients benefit from decreased requirements for gender-affirming hormone therapy, which reduces risks of drug-related side effects and improves quality-of-life. As patients preparing for vaginoplasty must often wait for a year or longer due to wait lists and requirements for hair removal, pre-vaginoplasty orchiectomy should be offered as an elective option. Potential benefits of decreased hormone requirements and partial alleviation of gender dysphoria and discomfort should also be discussed. Disclosure No