The longitudinal structural and acoustic effects of testosterone on the voice in trans and gender diverse speakers: A case series

Objective: Currently, gender-affirming hormone therapy (GAHT) with testosterone (T) is the default treatment for voice masculinization for trans and gender-diverse (TGD) assigned-female-at-birth individuals. However, there is limited evidence about what individuals can expect on T and why. The purpose of this study is to investigate the longitudinal effects of T on the voice in TGD individuals who are undergoing GAHT.

Methods: Thus far, two TGD participants undergoing GAHT with T completed a longitudinal study consisting of 13 time-points: one baseline visit before starting T and 12 monthly visits thereafter for one year. By the time of the conference, we anticipate full datasets for a total of seven participants. At each time-point, we collected structural magnetic resonance imaging (MRI) to measure anatomical changes of the vocal folds and vocal tract and speech recordings to measure acoustic changes. Analysis of MRI data included measurements of vocal fold length and width, and vocal tract length (VTL) at rest and during sustained phonation. Acoustic data included average fo during a reading passage, and estimated VTL derived from formant frequencies during sustained vowels.

Results: Over the course of one year on T, MRI-derived vocal fold width and length (mm) increased for both participants. For Participant 1 (P01), width increased from 6.5─ 8.1 mm, and length increased from 21.6─ 24.8 mm. For Participant 2 (P02), width increased from 5.8─7.7 mm and length increased from 19.5─ 20.7 mm. Average fo decreased for both participants: P01 decreased from 203.9─105.2 Hz (3.53 ST) and P02 decreased from 226.5─107.112 (3.9 ST). The largest fo change between consecutive months post-T occurred between months 1─ 2 for P01 and months 3─ 4 for P02. Results for structural VTL (at rest and during phonation) were mixed, and acoustic VTL estimates increased marginally. By the time of the presentation, structural and acoustic outcomes for all seven participants will be available and will be discussed quantitatively.

Conclusion: These preliminary observational findings will provide baseline information about what structural and acoustic changes to expect and when these changes may occur for TGD individuals seeking GAHT with T, informing evidence-based clinical voice care in this growing population.