OBJECTIVES To define the responses of stretched penile length (PL) to intramuscular testosterone enanthate (TE) treatment in prepubertal boys with hypospadias. METHODS We examined 17 Japanese boys with hypospadias at 1.4 ± 1.3 (mean ± SD) years of age. Their PLs were 2.79 ± 0.37 cm and -1.16 ± 0.88 SD of the mean. The etiology of hypospadias included sex chromosome disorders of sex development in 5, mastermind-like domain-containing 1 deficiency in 1, and unknown cause in the others. No mutation was identified in the SRD5A2 or AR gene. All the boys received as many as three intramuscular injections of TE 25 mg every 4 weeks (one injection in 3 boys, two in 5, and three in 9). RESULTS The TE treatment significantly increased PL by 1.01 ± 0.50 cm and 2.27 ± 0.99 SD (cm, P = .0002; SD, P = .0002). Age, body surface area (BSA), and PL before the treatment did not significantly correlate with the effect of TE treatment on PL. The effect of TE treatment on PL at the first injection in Japanese boys with hypospadias (0.35 ± 0.20 cm and 0.91 ± 0.62 SD) was significantly less than that in micropenis at 2.6 - 3.1 years of age (0.64 ± 0.26 cm and 1.37 - 0.68 SD) (cm, P = .0008; SD, P = .02). CONCLUSIONS These data indicate that (1) the intramuscular TE treatment significantly increases PL for hypospadias in prepubertal boys, with no demonstrable SRD5A2 or AR mutation; (2) age, BSA, and PL before the treatment are not significantly contributing factors to the effect of TE treatment; and (3) the effect of TE treatment for hypospadias is significantly less than that for micropenis.
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