Abstract Disclosure: R.L. Batista: None. M. Inacio: None. T.A. Bachega: None. N.L. Gomes: None. G. Madureira: None. M.C. Miranda: None. R.T. dallago: None. M.M. Ferrari: None. L.M. Lousada: None. J.A. Batatinha: None. E.F. Costa: None. M.P. Sircili: None. F. Denes: None. M.Y. Nishi: None. S. Domenice: None. B.B. Mendonca: None. Disorders/Differences of Sex Development (DSD) encompass a wide range of genetic conditions that affect sex development. Individuals with DSD may experience gender dysphoria and undergo gender changes throughout their lives. To analyze gender dysphoria and gender changes in individuals with DSD, we conducted a retrospective study involving all DSD cases from a single Brazilian tertiary medical center followed by a multidisciplinary team. We included 696 subjects considering their DSD diagnosis, sex assignment, age at DSD diagnosis, gender change, age at gender change, and phenotypic features. Among the three categories of DSD, chromosomal DSD was diagnosed in 264 subjects (135 with a 45,X karyotype, 101 mosaics with 45,X/46,Xi(Xq)), and three exhibited chimerism (all with ovotesticular DSD). Thirteen patients with chromosomal DSD and Y material were assigned as male, while two patients initially assigned as female underwent gender changes. Among the 258 subjects with 46,XY DSD, 69 had undetermined DSD, 64 had gonadal dysgenesis, 36 had 5-αRD2 deficiency, 18 had 17β-HSD3 deficiency, 11 had 17α-hydroxylase deficiency, 9 had Leydig cell hypoplasia, 25 had CAIS, 18 had PAIS, and 8 had AMH defects. Out of the 192 XY subjects with atypical genitalia, 89 (46%) were raised as female, and 13% changed from female to male, predominantly in cases of 5αRD2 deficiency (45%), followed by 17β-HSD3 deficiency (33%). Only 2.9% of those raised as male changed to female gender. Among the 46,XX DSD cases, congenital adrenal hyperplasia (CAH), mainly 21-hydroxylase deficiency, was diagnosed in 123 cases (115 initially assigned as female). Six cases of CAH resulted in gender changes from female to male, notably in the virilizing salt-wasting (VS) form (5/6; p=.004), all of which had a late onset of treatment (>2 years old) and poor compliance. Among the remaining 55 cases with 46,XX DSD, 24 had ovotesticular DSD (all with atypical genitalia), while 16 had 46,XX testicular DSD (seven with atypical genitalia); four cases underwent gender changes, with three changing from female to male. Twelve patients with 46,XX DSD had an undetermined diagnosis (all with atypical genitalia, three with syndromic features). Additionally, one patient had aromatase deficiency, one had POR deficiency, and one had glucocorticoid resistance syndrome. In conclusion, our study highlights a clear trend: gender changes, notably from female to male, were more prevalent in 46,XY DSD, particularly in 5αRD2 and 17β-HSD3 deficiencies. This underscores the importance of considering male sex assignment for individuals with these diagnoses. Additionally, factors such as the VS form of CAH, delayed treatment initiation, and inadequate compliance significantly contributed to female-to-male gender changes among 46,XX DSD cases. These findings offer critical insights guiding more effective and targeted interventions for DSD individuals. Presentation: 6/2/2024