Sunday, February 14, 2021

Testosterone therapy masculinizes speech and gender presentation in transgender men

Testosterone therapy masculinizes speech and gender presentation in transgender men. Carolyn R. Hodges-Simeon, Graham P. O. Grail, Graham Albert, Matti D. Groll, Cara E. Stepp, Justin M. Carré & Steven A. Arnocky . Scientific Reports volume 11, Article number: 3494 (2021). https://www.nature.com/articles/s41598-021-82134-2

Abstract: Voice is one of the most noticeably dimorphic traits in humans and plays a central role in gender presentation. Transgender males seeking to align internal identity and external gender expression frequently undergo testosterone (T) therapy to masculinize their voices and other traits. We aimed to determine the importance of changes in vocal masculinity for transgender men and to determine the effectiveness of T therapy at masculinizing three speech parameters: fundamental frequency (i.e., pitch) mean and variation (fo and fo-SD) and estimated vocal tract length (VTL) derived from formant frequencies. Thirty transgender men aged 20 to 40 rated their satisfaction with traits prior to and after T therapy and contributed speech samples and salivary T. Similar-aged cisgender men and women contributed speech samples for comparison. We show that transmen viewed voice change as critical to transition success compared to other masculine traits. However, T therapy may not be sufficient to fully masculinize speech: while fo and fo-SD were largely indistinguishable from cismen, VTL was intermediate between cismen and ciswomen. fo was correlated with salivary T, and VTL associated with T therapy duration. This argues for additional approaches, such as behavior therapy and/or longer duration of hormone therapy, to improve speech transition.

Discussion

Voice masculinization is particularly important to transgender individuals undergoing a female-to-male transition; compared with eight other masculinity traits, participants indicated that they were least satisfied with their voice prior to transition and ranked it highest in priority for seeing change. Further, after T therapy (which was effective at masculinizing fo and fo -SD in our participants), transmen were most satisfied with their vocal masculinization compared with other traits. Given its importance in a female-to-male transition and the growing number of individuals undertaking this treatment46,47, the need for evidence-based research on voice masculinization is high.

Our results show that, on average, T therapy is effective at masculinizing fo and fo-SD. Transmen’s fo values (mean and range) are comparable to those of cismen and statistically significantly lower than ciswomen’s fo values. While we do not have recordings of these men prior to T therapy, we can assume that their fo was close to the average for ciswomen and that their fo has since changed by 3.5 standard deviations (or more28), which is nearly 80 Hz. Research suggests that 50% of listeners can detect shifts as low as 1.2 semitones (e.g., 7 Hz for a 100 Hz voice42); therefore, these changes likely have a strong impact on perception of gender. Overall, the current findings are consistent with previous results documenting substantial changes in fo with T therapy in transmen32,33,34,35,36 and are suggestive of putative anatomical changes resulting from the action of T on the lengthening and thickening of vocal folds, similar to those occurring during puberty in natal males19,20,21,22,23,24. To understand the nature of these structural changes, future studies should use imaging techniques to objectively quantify vocal fold length and thickness at regular intervals during T therapy.

T therapy may not be sufficient for achieving formant frequencies that are indistinguishable from cismen. Our results showed that transmen’s estimated VTL was significantly longer than ciswomen but shorter than cismen. 23% of our participants’ VTL fell outside the range of our cismen sample, suggesting that T therapy alone does not fully masculinize larynx position. Despite research indicating that both fo and VTL contribute to gendered voice perception13,14,15,16, only one other published study on transmen’s voice changes has examined VTL or formants43. This motivates development of additional treatments, such as behavioral therapy, to increase objective speech masculinity by increasing vocal tract length48. Previous studies on transmen’s speech changes have shown that most changes have occurred prior to 9 months of continuous T therapy32,33,34,35,49; however, these studies did not examine changes in estimated VTL. This study is the first, to our knowledge, to demonstrate statistical differences in VTL between samples of transmen and cisgender speakers [see Cler et al.43 for a single, detailed case study and Papp44 for an unpublished dissertation].

Incomplete masculinization of VTL (as well as fo–SD) may partly explain why 17% of our participants reported that they were ‘neutral’ to ‘extremely dissatisfied’ with changes in their vocal masculinity. This accords with previous studies showing 12–16% of patients are not fully satisfied with their vocal transition and 25% were still sometimes perceived as female on the phone32,37. Further, 31% expressed interest in further masculinizing their speech through additional treatments like behavioral voice therapy32. Despite the need for behavioral voice therapy among transmen, only one published study has examined its efficacy48. This is in contrast to transfeminine individuals where it has been shown to help individuals express their gender identity through speech, reduce gender dysphoria, and improve mental health and quality of life50,51,52,53.

Some of the acoustic properties of speech that drive gender perception were associated with features of T therapy. We found a significant inverse association between salivary T and fo; however, the results appear largely driven by 3 data points (see Fig. 3). Given the small sample size, it is unclear whether these individuals represent the normal range of variation. The association between current salivary T and fo makes theoretical sense given the longer-term association between T administration and fo change in transmen, the presence of androgen receptors on the vocal folds54,55, and the associations between T and fo during puberty18,19,20,21,22,23. In addition, several studies have found links between salivary T and masculine vocal parameters in cismen25,26,28 (cf. Arnocky et al.29), and one study of cismen showed within-individual diurnal decreases in salivary T were associated with increases in fo27. Given the strong empirical and theoretical support for an association between T and fo, it is surprising that two previous studies on female-to-male speech changes35,36 did not find an association between serum T levels and fo.

Although there was not a significant association between salivary T and estimated VTL, T therapy duration was statistically significantly associated with VTL: longer T therapy durations were associated with longer estimated VTLs. This finding may suggest a longer-term relationship between T therapy and VTL. However, an alternative explanation is that this association reflects the confounding effect of time since transition given its close association with duration of T therapy. That is, even without formal voice training, transmen may be implicitly learning how to manipulate their vocal tract over time to achieve longer VTLs. Clinical studies on the relationships among dosing regimen, biological T availability, and speech parameters among transmen are necessary.

In summary, we see two important implications of these findings. First, a voice with a low pitch is a central aspect of masculine gender presentation because it is easily observable, highly sexually dimorphic, and difficult to approximate if not an adult male. Vocal fold dimorphism is one of the largest anatomical sex differences observed in humans (approximately 5 standard deviations28,56) and greater than any other extant ape57. Cisgender men and women differ by 60% in vocal fold length30 but only 8% in height58. Because vocal sexual dimorphism is extensive and, importantly, features little overlap in gender-typical vocal ranges, it is extremely difficult to speak in a voice consistent with the opposite sex, particularly in a sustained fashion31. These facts help explain why transmen are so dissatisfied with their fo prior to T therapy. Similarly, our participants were also highly dissatisfied with body fat distribution, which is also very dimorphic58,59, easily observable, and difficult to change without hormonal therapy.

A second implication of these findings is that more research on speech changes in transgender males is necessary. The studies that have been published are limited by small sample sizes32,33,34,49, a lack of a control group for comparisons32,33,35, and a focus on only fo34,49. Additional research on T dosing regimens as well as the efficacy of behavioral voice therapy are particularly necessary. Better evidence-based treatments for transmen have health and safety repercussions. Transgender individuals are disproportionately targets of violence and being viewed as one’s gender is likely a critical component for safety60,61,62,63. Approximately 20–47% of transgender individuals have been physically or sexually assaulted and an additional 34–46% have been verbally threatened or harassed62,64.

In contrast to voice masculinization, participants did not place high importance on seeing an effect of T therapy on the non-physical trait “psychological masculinity”, highlighting participants’ dissociation between their own perception of gender and outward display of gender prior to therapy65. This incongruence is a source of extreme distress, which is associated with higher levels of depression, anxiety, substance abuse, and suicidal ideation and attempts among the transgender population—particularly those that have not begun to transition5,7,9,65,66,67,68. Receiving hormone treatment significantly improves mental health, social health, and physical health outcomes in transgender populations2,7,9,66. Vocal congruence contributes to these improvements; Watt et al.2 showed that more masculine voices significantly contributed to improved well-being and mental health in female-to-male transgender patients.

To summarize, this research was designed with several goals in mind. First, we aimed to quantify the importance of voice change—relative to other masculine traits—for transgender men undergoing testosterone therapy. No previous studies have explored this question, in spite of the strong interest in voice change among the transmasculine population. Our results show that voice masculinization is of central importance to transgender individuals undergoing the female-to-male transition compared with eight other masculine traits. Second, we asked whether T therapy was effective at masculinizing three gendered speech parameters. Our results show that, on average, T therapy is effective at masculinizing fundamental frequency mean and variation (fo and fo-SD); however, transmen’s formant-based measure of vocal tract length (VTL) was significantly shorter than cismen. This study is the first, to our knowledge, to demonstrate statistical differences in VTL between samples of transmen and cisgender speakers. Third, we examined the association between salivary testosterone and vocal parameters. We found a significant inverse association between salivary T and fundamental frequency but no association with VTL. T therapy duration, however, was statistically significantly associated with VTL. These findings point to the need for more research on speech changes in transgender males—of particular importance are transition strategies that affect formant frequencies, which have largely been ignored in previous research.

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