Background: Exogenous androgen supplement is an optional treatment for micropenis; however, its use in childhood is controversial due to potential side effects.
Methods: Twenty-three children (mean age: 4.07±3.4 years) with micropenis of unknown causes harboring the 46,XY karyotype were recruited in an open prospective study. Androgen receptor (AR), steroid 5α-reductase-2 (SRD5A2), and SRY genes were sequenced; 2.5% dihydrotestosterone (DHT) transdermal gel (0.1-0.3 mg/kg/day) was applied and titrated within the normal DHT serum reference ranges. Stretched penile length (SPL) was measured before therapy, and after 1, 3 and 6 months of DHT gel treatment, respectively.
Results: Two patients were found with AR gene mutations and five patients with SRD5A2 gene mutations. Average stretched penile lengths (SPLs) were 1.68±0.6 cm at baseline and 2.2±0.66 cm, 2.6±0.59 cm and 2.9±0.55 cm (mean ± 1 SD) after 1, 3 and 6 months of treatment, respectively. Fourteen cases (61%) reached standard penile length ranges (>-2.5 SD) and medication was discontinued; six cases (26%) were satisfied with the improved penile lengths despite failing to reach the aged matched standards. Three infants (13%) discontinued the medication after 3 months due to anxiety about the potential side effects. No significant side effects were found except the elevated DHT serum levels after therapy.
Conclusions: Short term and local application of DHT at low doses in patients with micropenis could accelerate penile growth effectively without evident side effects; however, precautions still need be taken due to the paucity of long term study and the lack of ideal DHT dosage.
Keywords: AR; SRD5A2 gene; dihydrotestosterone gel; effect; micropenis; safety.