Context: Infertility observed in adult males with congenital adrenal hyperplasia (CAH) has been associated with testicular adrenal rest tumors (TART) that may originate during childhood.

Objective: To describe the prevalence of TART and Sertoli and Leydig cell function in a group of boys aged 2–10 years with CAH, and to compare prevalence with that of a control group.

Design: From August 2005 to January 2007, nineteen patients with classical CAH (CAH group) were referred from seven endocrinology centers.

Methods: We studied nineteen subjects in the CAH group and, as a control group, 13 boys from the community that did not have testicular diseases. A complete physical exam was performed. High-resolution ultrasound was used to determine TART prevalence. Inhibin B (Inh-B) and anti-Müllerian hormone (AMH) were used as Sertoli cell markers. The ratio between basal and 72 h post-hCG (5000 U/m²) treatment levels of testosterone [(T₇₂-T₀)/T₀] was used to evaluate Leydig cell response.

Results (median): CAH and control groups were comparable in chronological age (5.9 vs. 5.6; p=0.67) and bone age/chronological age ratio (1.09 vs. 1.03; p =0.09). TART prevalence was 4/19 (21%) in the CAH group. Lower values for Inh-B (49.2. vs. 65.2 pg/mL; p= 0.018), AMH (70.1 vs. 94.2 ng/mL; p= 0.002) and (T₇₂-T₀)/T₀ (5.6 vs. 13.6; p<0.01) were observed in the CAH group.

Conclusion: TART in prepubertal males with classic CAH could be found during childhood. We also report differences in markers of gonadal function in a subgroup of patients, especially in those with inadequate control.