<b><i>Introduction:</i></b> Testicular adrenal rest tumors (TART) are a known consequence for males with classical congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency. TART are associated with potential infertility in adults. However, little is known about TART in very young males with CAH. <b><i>Objective:</i></b> We assessed the presence of TART in newborn, infant, and toddler males with classical CAH via scrotal ultrasound. <b><i>Methods:</i></b> Males with CAH had scrotal ultrasounds during the first 4 years of life, evaluating testes for morphology, blood flow, and presence of TART. Newborn screen 17-hydroxyprogesterone (17-OHP) and serum 17-OHP at the time of ultrasound were recorded. Bone ages were considered very advanced if ≥2 SD above chronological age. <b><i>Results:</i></b> Thirty-one ultrasounds in 16 males were performed. An initial ultrasound was obtained in four newborns at diagnosis (6.8 ± 2.1 days), six infants (2.2 ± 0.9 months), and six toddlers (2.4 ± 0.9 years). Eleven males had at least one repeat ultrasound. A large proportion (11/16) were in poor hormonal control with an elevated 17-OHP (325 ± 298 nmol/L). One infant was in very poor hormonal control (17-OHP 447 nmol/L) at initial ultrasound, and two toddlers had advanced bone ages (+3.2 and +4.5 SD) representing exposure to postnatal androgens. However, no TART were detected in any subjects. <b><i>Conclusions:</i></b> TART were not found by scrotal ultrasound in males up to 4 years of age with classical CAH despite settings with expected high ACTH drive. Further research into the occurrence of TART in CAH may elucidate factors that contribute to the detection and individual predisposition to TART.

INTRODUCTION: Testicular adrenal rest tumors (TART) are a known consequence for males with classical congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency. TART are associated with potential infertility in adults. However, little is known about TART in very young males with CAH. OBJECTIVE: We assessed the prevalence of TART in newborn, infant, and toddler males with classical CAH via scrotal ultrasound. METHODS: Males with CAH had scrotal ultrasounds during the first 4 years of life, evaluating testes for morphology, blood flow, and presence of TART. Newborn screen 17-hydroxyprogesterone (17-OHP) and serum 17-OHP at the time of ultrasound were recorded. Bone ages were considered very advanced if ≥ 2SD above chronological age. RESULTS: Thirty-one ultrasounds in 16 males were performed. An initial ultrasound was obtained in four newborns at diagnosis (6.8 ± 2.1 days), six infants (2.2 ± 0.9 months), and six toddlers (2.4 ± 0.9 years). Eleven males had at least one repeat ultrasound. A large proportion (11/16) were in poor hormonal control with an elevated 17-OHP (325 ± 298 nmol/L). One infant was in very poor hormonal control (17-OHP 447 nmol/L) at initial ultrasound, and two toddlers had advanced bone ages (+3.2 and +4.5 SD) representing exposure to postnatal androgens. However, no TART were detected in any subjects. CONCLUSIONS: TART were not found in males up to 4 years of age with classical CAH despite settings with expected high ACTH drive. Further research into the occurrence of TART in CAH may elucidate factors which contribute to the detection and individual predisposition to TART.