ESPE2021 ePoster Category 1 Sex Endocrinology and Gonads A (10 abstracts)
Bilateral testicular regression: genetic etiology and outcome in a large Belgian series
Lloyd Tack 1 , Cécile Brachet 2 , Claudine Heinrichs 2 , Emese Boros 2 , Kathleen De Waele 1 , Saskia vander Straaten 1 , Sara Van Aken 1 , Margarita Craen 1 , Annelies Lemay 3 , Anne Rochtus 4 , Kristina Casteels 4,5 , Dominique Beckers 6 , Thierry Mouraux 6 , Elfride De Baere 1 , Hannah Verdin 1 & Martine Cools 1
1Ghent University Hospital, Ghent, Belgium; 2Université Libre de Bruxelles, HUDERF, Brussels, Belgium; 3AZ Turnhout, Turnhout, Belgium; 4University Hospitals Leuven, Leuven, Belgium; 5KU Leuven, Leuven, Belgium; 6Centre Hospitalier Universitaire UCL, Namur, Belgium
Background: Bilateral testicular regression (BTR) is characterized by the absence of both testicles in a newborn male or shortly thereafter, and presenting as bilateral cryptorchidism with undetectable AMH levels and the absence of Müllerian structures on pelvic ultrasound. Depending on when the regression occurs during fetal development, the condition can be associated with a micropenis. Few studies have explored the etiology and long-term outcome of BTR.
Methods: Cross-sectional study of boys/men with BTR (n = 31) recruited in five Belgian centers at an age of 14.3±5.4years. During the study visit a clinical and genital exam was performed. Data regarding initial presentation and management were collected retrospectively. Genetic analysis: exome-based testing of genes (n = 241) involved in gonadal development and spermatogenesis.
Results: All had bilateral absent testes or non-functional testicular remnants. Seven out of 31 boys had associated micropenis. BTR diagnosis was established by laparoscopy in 11/31 (35.5%), low AMH levels in 7/31 (22.6%), an hCG-stimulation test in 9/31 (29%) or a combination of these in 4/31 (12.9%). Nine (29%) boys received IM Sustanon during childhood (25-50mg/month for 3-6months) at a median age of 6 months, with limited or no effect in two. Testosterone replacement was initiated in 21/31 (67.7%) at a median age of 12.4years (IQR: 1.3). At the study visit, fourteen had reached Tanner 4-5, and six (42.9%) had bilateral testis prostheses placed at a mean age of 16.5±0.9years. Mean stretched penile length at the end of puberty was 10.0±2.6cm, representing a mean penile growth of 3.9±1.4cm over the course of treatment and a persistent micropenis (<7.5 cm) in one. Only 1/14 had a final height below his midparental height range. Genetic analysis revealed heterozygous (likely) pathogenic variants in DHX37 (p.Arg334Trp and p.Arg308Gln) in two cases, respectively. Both had a distinct phenotype, with a severe micropenis (10-20mm) which showed limited to absent response to (dihydro)testosterone treatment during infancy. One of them developed unilateral neurosensory hearing loss at the age of 8 years. No other (likely) pathogenic variants were found in this cohort.
Conclusion: Pubertal height gain and penile growth with testosterone supplementation are generally satisfactory in BTR. The previously reported involvement of DHX37 in the etiology of BTR was confirmed in two cases, who both had a micropenis and no response to (dihydro)testosterone in infancy. Further studies are needed to determine whether DHX37 variants characterize a specific subgroup of BTR with severe undervirilization and possible extra-testicular manifestations.
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