Addition of testosterone to endocrine care for transgender women: a dose-finding and feasibility trial.

Transgender women who underwent gonadectomy have lower serum testosterone concentrations than cisgender women, creating a physiological rationale for supplementation.

• The study targeted serum testosterone concentrations between 1.5 and 2.5 nmol/L, representing the cisgender female physiological range.
• The study population consisted of transgender women who had undergone gonadectomy.
• This concentration gap provided the basis for investigating testosterone supplementation in this population.

Most participants required the lowest or second-lowest dose of testosterone gel to reach target serum concentrations of 1.5-2.5 nmol/L.

• The dose-titration phase used 2-week intervals with doses of 0.07, 0.09, or 0.13 mL (277, 318, or 403 µg bioavailable testosterone respectively).
• Most participants required a dose of 0.07 mL (277 µg bioavailable testosterone) or 0.09 mL (318 µg bioavailable testosterone) to reach target concentrations.
• The study used transdermal testosterone 2% gel (Tostran®) applied daily.
• 12 participants were included in total.

Testosterone concentrations remained stable throughout the study once an individualized dose was established.

• After the dose-titration phase, the established dose was continued for 8 weeks.
• Testosterone was measured every 2-4 weeks during the study.
• Stable testosterone levels within the target range of 1.5-2.5 nmol/L were maintained during the 8-week continuation phase.

Changes in clinical outcomes were in the desired direction and side effects were mild.

• Laboratory analyses, side effects, and clinical symptoms were evaluated throughout the study.
• Cardiovascular parameters, virilizing side effects, and clinical symptoms were among the explored outcomes.
• Side effects were described as mild.
• Changes in clinical outcomes were reported as being 'in the desired direction.'

Testosterone supplementation in transgender women was found to be feasible and safe in the short term, but requires personalized dose titration.

• The study was an open-label, single-arm feasibility study with 12 participants.
• Dosing requires personalized titration as individual responses varied.
• The authors concluded that a blinded, placebo-controlled, randomized clinical trial is needed to study clinical benefit.
• The study duration included a titration phase with 2-week intervals followed by an 8-week continuation phase.