Background
An estimated 1.4 million persons in the United States identify as transgender or nonbinary, signifying that their gender identity does not correspond with their assigned sex at birth. Individuals assigned female at birth may seek gender-affirming hormone therapy with testosterone. No studies have directly examined ovulatory function in transmasculine individuals using injectable testosterone.
Objectives
Our primary objective was to determine the effect of testosterone on ovulatory suppression in transmasculine individuals. Secondary objectives were to determine predictors of ovulation in transmasculine individuals on testosterone, and to assess the effect of testosterone on antimüllerian hormone.
Materials and Methods
This prospective observational study recruited participants from a community clinic that provides gender-affirming hormone therapy. Enrolled individuals were assigned female at birth and were currently using or seeking to initiate masculinizing therapy with injectable testosterone esters (transmasculine individuals). Over a 12-week study period, participants collected daily urine samples for pregnanediol-3-glucoronide testing and completed daily electronic bleeding diaries. We assessed monthly serum mid-dosing interval testosterone, estradiol and sex hormone binding globulin, and antimüllerian hormone values at baseline and study end. Ovulation was defined as pregnanediol-3-glucoronide greater than 5 μg/mL for 3 consecutive days. The primary outcome was the proportion of participants who ovulated during the study period. We examined predictors of ovulation such as age, length of time on testosterone, serum testosterone levels, body mass index, and bleeding pattern.
Results
From July to November 2018, we enrolled 32 individuals; 20 completed the study (14 continuing testosterone users, 6 new users). Median age was 23 years (range 18−37 years). Bleeding or spotting during the study period was noted by 41% of participants (13/32). Among continuing users, median testosterone therapy duration was 11 months (range 1−60 months). A single ovulation was observed out of a total of 61 combined months of testosterone use; however, several transient rises in pregnanediol-3-glucoronide followed by bleeding episodes were suggestive of 7 dysfunctional ovulatory cycles among 7 individuals. There was no difference in antimüllerian hormone from baseline to 12 weeks between participants initiating testosterone and continuing users of testosterone. We did not have the power to examine our intended predictors given the low numbers of ovulatory events, but found that longer time on testosterone and presence of vaginal bleeding over 12 weeks were associated with transient rises in pregnanediol-3-glucoronide.
Conclusion
This study suggests that testosterone rapidly induces hypothalamic−pituitary−gonadal suppression, resulting in anovulation in a proportion of new users. Importantly, these data also suggest that some long-term testosterone users break through the hormonal suppression and experience an ovulatory event, thereby raising concerns pertaining to the need for contraception in transmasculine individuals engaged in sexual intercourse with sperm-producing partners. Given the small number of overall participants, this work is hypothesis generating. Larger studies are needed to confirm and to clarify these findings.
Gender dysphoria refers to the distress or discomfort an individual experiences when their assigned birth sex is incongruous with their gender identity. Available treatment options for gender dysphoria include cross-sex hormone therapy and gender-affirming surgery. Individuals may seek out 1, both, or neither of these therapies in the course of their gender transition. There is a broad range of identities and preferred terminology to characterize this population. For clarity and consistency, we use the term “transmasculine individuals” to refer to individuals assigned female at birth who are seeking masculinizing gender-affirming care. It is estimated that there are 1.4 million transgender or nonbinary (TNB) individuals in the United States, defined as individuals whose gender identity does not correspond to their sex assigned at birth. Data suggest that the overall number of transmasculine individuals seeking hormone therapy is increasing. Many transmasculine individuals seek hormone therapy without plans to proceed with eventual hysterectomy, , yet data on fertility and family planning in this population are exceedingly limited.
Why was this study conducted?
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The effect of testosterone on ovulation is unknown, and the direct effect of testosterone has not been examined in transmasculine individuals
Key findings
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Testosterone leads to ovulatory dysfunction and rapidly induces anovulation.
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Testosterone levels did not significantly affect antimüllerian hormone (AMH).
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Bleeding is uncommon after 6 months. However vaginal bleeding may indicate persistent breakthrough ovulatory events.
What does this add to what is known?
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This is the first study to directly assess ovulatory status of transmasculine individuals on testosterone.
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These results suggest that rapid ovulatory suppression after testosterone initiation is common.
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More data are needed to understand the timeline and mechanism of ovulatory suppression, and the clinical significance with regard to fertility and long-term health consequences.
Much of the research assessing fertility in TNB communities has focused on fertility-sparing options for those desiring a biological child. Contraception for those individuals not currently desiring fertility is often overlooked, frequently due to the assumption that transmasculine individuals do not have sexual relationships that could result in pregnancy. However, it is common for transmasculine individuals to have cisgender male partners. Limited data suggest that condoms are the most common form of contraception in this population, although some transmasculine individuals do use hormonal contraceptives. , , In addition to potential dysphoria associated with pregnancy in a transmasculine individual, testosterone can cause virilization of female fetuses and is categorized as a teratogen. Therefore, gaining a better understanding of contraceptive needs of this population is an important goal. Despite nearly universal amenorrhea within months of initiating testosterone therapy, unplanned pregnancies have been documented, and some individuals who stop testosterone to become pregnant have conceived prior to return of menses.
To our knowledge, no prior studies in transmasculine individuals have assessed ovulation during testosterone use. Fertility potential during testosterone use and after cessation is not well characterized. Assessment of hormonal cycles through measurement of urinary hormone metabolites has been validated in a wide variety of medical conditions. Daily measurement of urinary pregnanediol-3-glucoronide (PdG) specifically for evidence of luteal activity has shown excellent utility for retrospective confirmation of ovulation. This noninvasive method charts hormonal cycles and assesses individuals longitudinally for evidence of ovulation. This prospective cohort study of transmasculine individuals used daily urinary PdG measurements over a 12-week period to monitor ovulatory events in new and continuous transmasculine individuals using injectable testosterone. Findings of this study provide insight into the effect of exogenous testosterone on ovulatory function and the need to counsel transmasculine individuals about the risks for unintended pregnancy and the need for an effective contraceptive method.
Materials and Methods
Study population
Participants were recruited from a community clinic with 3 sites in the Seattle, Washington, metropolitan area. Participants assigned female at birth currently using or planning to initiate masculinizing therapy with injectable testosterone were eligible for the study if they had not undergone hysterectomy or oophorectomy, were currently on or initiating injectable testosterone therapy, and had monthly menses prior to the initiation of hormone therapy. Exclusion criteria included use of any form of hormonal contraception in the past 3 months, treatment with a gonadotropin-releasing hormone (GnRH) agonist, current use of finasteride, or use of topical testosterone because of inconsistency with absorption and variable dosing. All individuals used weekly injectable testosterone cypionate at a dose of 50−100 mg either intramuscularly, subcutaneously, or a combination, based on current guidelines for gender-affirming care. Given the lack of previous data, the sample size was based on precision estimates. We estimated that to detect 4 ovulatory events, 30 participants would be required to detect an ovulation rate of 13.3% (95% confidence interval 5.1−30.6%). Written informed consent was obtained from all participants. Study procedures were approved by the University of Washington Institutional Review Board (HSD 4261).
Data collection
Baseline surveys collected demographic data, medical, sexual, and menstrual histories, fertility plans, and experience with fertility and contraception counseling. The survey was developed in conjunction with a TNB health expert and community member with experience developing gender-affirming care guidelines for multiple health systems. Gender and sexual identity categories were free text and then collapsed into categories for data analysis. Participants’ medical records were abstracted to confirm body mass index (BMI), medical history, current medications, and testosterone dosing. At the enrollment visit, participants had their blood drawn for testosterone, estradiol, sex hormone binding globulin (SHBG), and antimüllerian hormone (AMH). Participants were provided with urine collection kits with detailed instructions for collection and storage. Participants collected daily first-morning urine specimens for the entire 12-week study period. If this was not possible, urine collection occurred as early as possible in the day. Participants stored urine in 2-mL tubes in their home freezer. They received daily text message reminders and were given the opportunity to report any irregularities in their urine collection for that day, for example, a late collection. For new users, they were instructed to begin urine collection when they began testosterone injections, and this was considered day 1 of participation. Continuing users of testosterone were instructed to begin urine collection immediately following study entry. Data on daily bleeding patterns were collected via text message; a paper bleeding diary served as back-up. Definitions of bleeding and spotting were based on World Health Organization (WHO) guidelines developed for contraceptive studies.
Follow-up visits were scheduled on the participant’s mid-dosing interval day (either 3 or 4 days after injection) at 4 weeks, 8 weeks, and 12 weeks at a site that was convenient for the participant. At each follow-up visit, blood was collected for testosterone, estradiol, and SHBG, and a short online survey about health updates and testosterone dosing was completed (at home or in clinic). In addition, participants turned in urine specimens collected since the last visit or retained them until study completion. The 12-week visit also included a blood collection for AMH and a final survey.
Data management
Data were collected and managed using Research Electronic Data Capture (REDCap) electronic data capture tools hosted at the Institute of Translational Health Science at the University of Washington. REDCap is a secure, Web-based application designed to support data capture for research studies.
Laboratory analysis
Serum samples were sent to LabCorp (Burlington, NC). Testosterone, estradiol, and SHBG were analyzed via electrochemiluminescence immunoassay per LabCorp protocol. AMH was analyzed via electrochemiluminescence.
When participants returned urine specimens to study staff, they were stored at the University of Washington at −80°C until all specimens were collected and ready for analysis. They were shipped on dry ice to the Oregon National Primate Research Center where they were analyzed for urinary PdG using enzyme-linked immunosorbent assay (ELISA; Arbor Assays). The criterion for ovulation was defined as urinary PdG greater than 5 μg/mL for 3 days.
Statistical methods
The primary outcome was the proportion of patients who ovulated, defined as urinary PdG greater than 5μ g/mL for 3 days, which has been shown to have a sensitivity of 81% and specificity of 100% when compared to transvaginal ultrasound confirmation of ovulation. Secondary outcomes were the (1) proportion of months during which participants ovulated, (2) AMH change from baseline to 12 weeks, and (3) correlation between ovulation and age, duration of testosterone use, BMI, and the presence of vaginal bleeding.
We calculated the proportion of transmasculine individuals ever experiencing ovulation over the study period and the proportion of months in which ovulation was observed. We performed univariable logistic regression to determine the relationship between ovulation and secondary outcomes and multivariable logistic regression analysis to identify predictors of ovulation such as serum hormone levels or BMI. The change in AMH at baseline and 12 weeks was calculated for each study participant. Change in AMH among new users vs continuing users was compared using independent, 2-sample t tests.
Data analysis was performed using R statistical software version 3.4.1 (2017 R Foundation for Statistical Computing, Viena, Austria).
Results
Baseline characteristics
Of the 109 individuals approached, 32 were enrolled; 46 of 109 were ineligible, 26 of 109 declined participation, and 5 of 109 were excluded for other reasons ( Figure 1 ). In all, 22 participants completed at least 4 weeks and 20 completed 12 weeks of data collection. Of the 10 participants who discontinued the study with a known reason, 1 individual discontinued because of starting twice-weekly testosterone injections; the remaining participants discontinued because of an inability to make study visits or to complete study activities.
