Micropenis (stretched length more than or equal to -2.5 SD below the mean value) can result from fetal testosterone and/or growth hormone deficiency. Controversy has focused on the capacity of testosterone treatment to induce a functionally adequate adult phallus which has led some clinicians to recommend sex reversal in affected infants. We studied 8 patients with striking micropenis: 5 with multiple pituitary hormone deficiencies (MPHD) and 3 with Kallmann syndrome (KS) to maturity (ages 18-27 years). At presentation, the mean stretched penile length in the 5 patients with MPHD (ages 4 months - 14 years) was 1.6 cm (-3.9 SD). The 3 patients with KS had a mean stretched penile length of 2.4 cm (-3.5 SD), (ages 7 months, 6 years and 14 years). The mean penile length at presentation for both groups was -3.7 SD. All patients received one or more courses of testosterone enanthate IM every 4 weeks (25 or 50 mg) in infancy and childhood to induce phallic growth and, at the age of puberty the dose was gradually increased to 200 mg monthly. The normal Caucasian adult stretched penile length is 12.4 cm ± 2.7 cm (Wessel et al, J Urol 156: 995, 1996). As adults, our 8 patients had attained a mean final stretched penile length of 10.3 cm ± 2 cm (-0.8 SD below the normal mean value), with a range of 8-14 cm, median 9.75 cm. This represents a mean catch up of +3 SD in penile length from that at presentation. In this small series, there was no apparent correlation between the initial penile length or the age at initiation of therapy and the final penile length.

The results in this group of hypogonadotropic hypogonadal males indicate that testosterone therapy in infancy and childhood can augment phallic size in patients with microphallus secondary to fetal testosterone deficiency and result in a functionally normal adult penilc size.