Effects of exogenous testosterone therapy on communication in gender diverse speakers - Project Summary Gender-diverse (GD) individuals are underserved, targets of violence, and at higher risk for negative health outcomes. Although up to 66% of GD individuals are assigned female at birth (AFAB) and up to 97% of these individuals have gender-related voice problems, there is no evidence-based treatment for voice masculinization, a critical factor in gender-affirming medical intervention and personal safety. Most clinicians and many patients are left to assume that gender-affirming hormone therapy with testosterone (T) is the only path toward voice change. The current speculation is that T leads to an increase in the size of the vocal folds, leading to lower fundamental frequency (fo), and thus to voice masculinization. However, this theory has not been directly assessed, and T is likely to cause additional structural changes to the larynx and vocal tract that may impact both self- and listener vocal-perception of gender (VPoG). In summary, despite a critical health need in an at-risk population, there is a lack of evidence supporting this common voice treatment for GD-AFAB individuals. The goal of this proposal is to evaluate our conceptual model of voice and speech in GD-AFAB speakers: 1) that T results in anatomical changes in vocal fold length, vocal fold thickness, and vocal tract length, decreasing voice fo and speech formants, which leads to changes in VPoG; and 2) that individual characteristics are related to the degree of VPoG changes with T. This observational study will follow GD- AFAB adults who are being treated with T as part of their normal clinical care to systemically test this model. In Aim 1, we will longitudinally characterize the effects of T in GD-AFAB individuals, providing unprecedented understanding of the actual impact of this common treatment at the group level. In addition to anatomical, physiological, and acoustical measures, perceptions of both self and others will be included to account for potential misalignment of these perceptions, which are equally important outcome measures of voice modification [8, 99]. This aim will provide evidence-based expectations about voice masculinization for individuals considering the use of T. Aims 2 and 3 will examine changes in VPoG at the individual level, regardless of group-level findings in Aim 1. In Aim 2, we will define the anatomical, physiological, and acoustical changes associated with changes in VPoG with T. This aim will identify how T modifies communication, which will allow for objective outcomes and therapeutic targets in future clinical trials. Finally, in Aim 3, we will determine participant characteristics that are associated with changes in VPoG with T, providing more precise expectations about individual treatment responses. Together, these aims will provide a roadmap for future evidence-based treatment: clinicians will be able to provide guidance about when, how, and in whom communication will be impacted by T.
