Table 1.

Results of longitudinal studies in trans men before and after testosterone therapy.

Study	N	Task	Speaking fo change	Steepest change	Other measures
7Van Borsel	2	/ɑ/ and Reading	200–220Hz to 130–160Hz	4 mo	Jitter = Shimmer = PFR=*
12 Damrose	1	/ɑ/	228 to 113 Hz	3–4 mo	Shimmer ^ NHR ^ PFR=*
13 Deuster	11	Reading	79.4Hz (8.78ST)	2–3 mo
5Nygren	50	Reading	192 to 125Hz		PFR=
14Irwig & 16Hancock	7	/ɑ/, Reading	135–183 to 87–128Hz (mean: −6.4 ST)		Jitter v Shimmer v NHR ~ PFR=
17Zimman	3	Reading	167–177Hz to 122–132Hz		First three formants (F1–3) ~

PFR: phonatory frequency range (maximum and minimum f_o that the speaker can produce)

NHR: noise-to-harmonic ratio

^*Authors suggest that PFR reduced, but recalculating results in ST rather than Hz shows a stable PFR (<10% change)

Key

^=:(average participant shows) no change;

^{^:}increased;

^v:decreased;

^~:inconsistent between participants