Prevalence and Changes in Genetic and Clinical Characteristics in Growth Hormone-Treated Belgian Girls with Turner Syndrome: A Study from the BELGROW Registry

INTRODUCTION: Since the first description of Turner syndrome (TS), both genotypic spectrum and phenotypic presentation have evolved. This study aimed to examine trends in this evolution over the past three decades and provides an overview of current genetic and clinical features in a large nationwide multicenter cohort of girls with TS. METHODS: We analyzed data from growth hormone (GH)-treated girls with TS included in BELGROW, the national GH registry of the BELux Society for Pediatric Endocrinology and Diabetology, between 1985 and 2022. Karyotype, age at diagnosis, and phenotype were studied in 716 girls. Two periods were compared: 1991-2002 (group 1, n = 250) and 2003-2017 (group 2, n = 270). RESULTS: The annual number of girls with TS starting GH remained stable (mean n = 19/year). In the entire cohort, monosomy 45,X was the most frequent karyotype (44%), followed by structural anomalies of the X chromosome (27%), 45,X/46,XX mosaicism (13%), triple X mosaicism (4%), 45,X/46,XY or complex Y anomalies (6%), and others (6%). The proportion of 45,X decreased between the two periods (46%-38%, p < 0.05). Overall, median age at diagnosis was 6.4 years with 7.6% of girls diagnosed prenatally, 24% before age 1, 49% in childhood, and 19% after 12 years. Prenatal diagnoses increased from 2.5% (group 1) to 15% (group 2) (p < 0.001). Girls with a 45,X karyotype were diagnosed earlier than girls with other genotypes (median 2.2 vs. 8 years, p < 0.001). Skeletal (73%), neurosensory (60%), and cardiac (29%) systems were most affected. Skeletal and cardiac malformations were more frequent in girls with a 45,X karyotype (p < 0.05 and p < 0.01, respectively). CONCLUSION: Genotype distribution and timing of TS diagnosis have significantly changed since 1991, while the annual number of girls starting GH therapy has remained stable. A 45,X karyotype is associated with earlier diagnosis and more comorbidities.