简介：AbstractImportance:Children with 5-alpha-reductase deficiency (5α-RD) and hypospadias present with micropenis, which makes it difficult to obtain sufficient tissue for urethral reconstruction.Objective:We investigated the therapeutic effects of oral testosterone undecanoate and established a standard androgen treatment protocol for patients with 5α-RD with micropenis.Methods:Patients with 5α-RD were treated with oral testosterone undecanoate for 3 months as a course. All patients were treated with no more than 3 courses. If the penile length (PL) reached 2.5 cm (the minimum criterion for surgery) or greater than or equal to -2.5 standard deviations (SDs) (lower limit of normal), testosterone undecanoate was considered to be effective.Results:The median age of 90 patients with 5α-RD was 1.7 years (0.9, 3.1 years). The baseline PL was 1.9 ± 0.6 cm before treatment. At the end of the first course, the PL of 63 patients (70%) reached 2.5 cm, and 49 patients (54%) reached greater than or equal to -2.5 SDs. After two treatment courses, the PL of 81 patients (90%) reached 2.5 cm, and 90 patients (100%) reached greater than or equal to -2.5 SDs. After three courses, the PL of all patients reached 2.5 cm, and all patients reached a PL greater than or equal to -2.5 SDs. No abnormal increase was observed in height-SD score, weight-SD score, or ratio of bone age to chronological age during the 1-3-year follow-up.Interpretation:After 3-9 months of treatment, PL increased to the target length. No severe adverse reactions were observed during follow-up. Testosterone undecanoate was safe and effective in children with 5α-RD with micropenis.