Mutational disorder (MD) and gender identity disorder (GID) are rare disease. Such patients tend to complain that their speaking fundamental frequency (SFF) does not fit, being too high or too low. Type 3 thyroplasty (TP3) reduces the pitch of the SFF. In detail, the tension of the vocal fold is loosened by TP3, which then causes the the SFF to become low-pitched. Type 4 thyroplasty (TP4) conversely increased the pitch of the SFF as the tension of the vocal fold is tightened causing the SFF to become high-pitched. While vocal pitch disorders are not life-threatening for patients with MD and GID, they can cause substantial worry and stress. TP3 and TP4 can thus improve the quality of life of the patients with MD and GID.
