Margot Morssinkhof

Chapter 1 18 There are, generally speaking, two forms of GAHT: masculinizing and feminizing hormones. Masculinizing GAHT is used by transmasculine (TM) persons who were assigned female at birth, and it consists of the use of testosterone. Feminizing GAHT is used by transfeminine (TF) persons who were assigned male at birth, and it generally consists of the use of estradiol and anti-androgens. In persons using masculinizing GAHT, who still have a uterus, ovulation is not always suppressed (Taub et al., 2020), and it is also possible to use medication to suppress ovulations or suppress menstrual bleeding using progestins or hormonal contraceptives. The effects of GAHT on the HPG-axis and daily hormone fluctuations are also illustrated in Figure 1.1 and 1.2. Figure 1.2. Image of hormone levels in a 28-day cycle without use of exogenous hormones compared to hormone levels during use of Gender-Affirming Hormones and Oral Contraceptives. The left panel (yellow) displays the endogenous hormone levels in females (top panel) and males (bottom panel). The middle panel displays hormone levels in users of oral contraceptives, with stable daily fluctuations of progesterone and estradiol for 21 days and a steep reduction in estradiol and progesterone in the placebo week. The right panel (blue) displays possible hormone fluctuations in GAHT users: the top panel displays hormone levels after masculinizing hormone use, with low progesterone levels and either small daily fluctuations (in users of testosterone gel) or a fluctuation over the course of 3 weeks (in users of testosterone injections), as well as partial but not full suppression of progesterone. The possible 12-week fluctuation in testosterone levels in users of long-acting testosterone is not displayed. The bottom panel displays hormone levels after feminizing hormone use, with low testosterone levels and either daily fluctuations in estrogen (in users of estradiol forms used daily) or multiday fluctuations (in the case of estradiol plasters, which are used biweekly). Created using Biorender.com.

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