Cross-Sex Hormone Therapy Is Associated With Loss of Circadian Rhythm in the Male Rat.

BACKGROUND

Transgender women are individuals born male but identify as female. Many transgender women undergo gender-affirming hormone therapy to alleviate the distress that can occur due to gender incongruence. For transgender women, gender-affirming hormone therapy includes 17β-estradiol (E2) combined with an antiandrogen therapy (AA) or surgical intervention. Numerous studies suggest that the risk of cardiovascular disease is elevated in transgender women; yet, the biological effects of gender-affirming hormone therapy on cardiovascular health are unknown. We hypothesize that a shift in the hormonal milieu versus natal sex in the male rat is associated with an increase in blood pressure at baseline and an enhanced responsiveness to a hypertensive challenge.

METHODS

We developed clinically relevant models that mimic gender-affirming hormone therapy combination therapies utilized for the endocrine treatment of gender dysphoria in transgender women.

RESULTS

Chronic E2 plus castration or the E2+antiandrogen spironolactone was associated with a significant reduction in lean mass and testosterone. At baseline, 24-hour mean arterial pressure did not differ in E2+castration or E2+antiandrogen therapy versus control, but circadian rhythm was disrupted. In response to chronic Ang II (angiotensin II; 200 ng/kg per minute), the Ang II-induced increase in blood pressure was attenuated in E2+castration compared with control, but the blood pressure response to Ang II was similar in E2+antiandrogen therapy versus control.

CONCLUSIONS

Thus, these data indicate that the type of combination therapy utilized may exert differential effects on blood pressure and that disruption of circadian rhythm may be a contributory factor to the increased risk of adverse cardiovascular outcomes in transgender women exposed to high 17β-estradiol coupled to androgen suppression.