Muscle Strength, Size, and Composition Following 12 Months of Gender-affirming Treatment in Transgender Individuals

Abstract

Context As many sports are divided in male/female categories, governing bodies have formed regulations on the eligibility for transgender individuals to compete in these categories. Yet, the magnitude of change in muscle mass and strength with gender-affirming treatment remains insufficiently explored. Objective This study explored the effects of gender-affirming treatment on muscle function, size, and composition during 12 months of therapy. Design, settings, participants In this single-center observational cohort study, untrained transgender women (TW, n = 11) and transgender men (TM, n = 12), approved to start gender-affirming medical interventions, underwent assessments at baseline, 4 weeks after gonadal suppression of endogenous hormones but before hormone replacement, and 4 and 12 months after treatment initiation. Main outcome measures Knee extensor and flexor strength were assessed at all examination time points, and muscle size and radiological density (using magnetic resonance imaging and computed tomography) at baseline and 12 months after treatment initiation. Results Thigh muscle volume increased (15%) in TM, which was paralleled by increased quadriceps cross-sectional area (CSA) (15%) and radiological density (6%). In TW, the corresponding parameters decreased by –5% (muscle volume) and –4% (CSA), while density remained unaltered. The TM increased strength over the assessment period, while the TW generally maintained their strength levels. Conclusions One year of gender-affirming treatment resulted in robust increases in muscle mass and strength in TM, but modest changes in TW. These findings add new knowledge on the magnitude of changes in muscle function, size, and composition with cross-hormone therapy, which could be relevant when evaluating the transgender eligibility rules for athletic competitions.

Transgender Women in the Female Category of Sport: Perspectives on Testosterone Suppression and Performance Advantage

“…Including Gooren and Bunck [62], 12 longitudinal studies [53,[63][64][65][66][67][68][69][70][71][72][73] have examined the effects of testosterone suppression on lean body mass or muscle size in transgender women. The collective evidence from these studies suggests that 12 months, which is the most commonly examined intervention period, of testosterone suppression to femaletypical reference levels results in a modest (approximately − 5%) loss of lean body mass or muscle size (Table 4).…”

A novel predictive score for citrate accumulation among patients receiving artificial liver support system therapy with regional citrate anticoagulation

“…This helps to explain the positive correlations between LDCA and gender, serum creatinine, and PT-INR. LDCA may be more likely to occur in female patients because, on average, men have more muscle mass than women, allowing for more citrate metabolism in muscle cells 22 . As serum creatinine is a marker for renal function, it is expected that both citrate and serum creatinine levels will be high if metabolism in the kidneys is slowed.…”

The Effects of Gender Affirming Treatment on the Sporting Performance and Muscle Memory of Transgender Athletes. A Protocol for The Tavistock Transgender Athlete Study.

“…Previous studies have addressed the effects of androgen deprivation therapy and GAT in transwomen [18][19][20][21][22] and transmen [20,[22][23][24]. Loss of muscle mass has been shown in transwomen [19][20][21][22] and gains in muscle mass have been shown in transmen [20,22]. Early studies showed that gonadal suppression in men resulted in decreased muscular strength [18], however, a more recent study showed that transwomen had no change in muscle strength [22].…”