Testosterone Treatment for Micropenis, Should It Be Delayed?

In a study published in 1995, named "Micropenis: does early treatment with testosterone do more harm than good", researchers examined whether or not testosterone treatment should be applied immediately in boys born with a micropenis or if it should be delayed for a couple of years.

The study was carried out on a rodent model for micropenis.

The micropenis condition (along with hypogonadotropic hypogonadism) was induced to the rats using long acting microspheres of the gonadotropic agonist leuprolide acetate. By the way, I have no idea what this means, I am just copy pasting the original paper. Please leave a comment if you want to explain this in simple words!

the study was carried out with rats with micropenis
The study was carried out on rats with induced micropenis
Next, the rats were divided into 4 groups, each given testosterone treatment at the age of 7, 28, 56 (pre-puberty) and 84 (puberty) days respectively.  There was a fifth group as well, that was given no treatment to compare the findings of the other groups (control group).

According to the study's findings, testosterone treatment given at the age of 7 resulted in premature penile growth and the reappearance of micropenis later in adulthood!

 In comparison, the last two groups in which the treatment was delayed, presented with complete penile development, and a normal penis size. The study strongly indicates that testosterone exposure should be delayed in childhood as it may result in penile length reduction during adulthood.

It should be mentioned that although rats are a good predictor for how humans would react on something, they are just that, a good predictor.

Sometimes results derived from rat models simply can't predict the results of a similar study on human subjects. In this case, afew years later, another similar study - this time on humans - was published and showed that the sooner testosterone therapy is applied the better the final result!

The abstract of the study reads as following:

Micropenis secondary to hypogonadotropic hypogonadism was induced in the Sprague-Dawley rat using long acting microspheres of the gonadotropic agonist leuprolide acetate. Following the induction of micropenis treatment was initiated with testosterone at day 7, 28, 56 or 84 of life. All treatment protocols resulted in improved phallic growth compared to the untreated animals with micropenis (p < 0.01). Treatment of animals with testosterone beginning on day 7 of life resulted in premature growth of the penis and the redevelopment of micropenis in adulthood. In contrast, delaying testosterone therapy until day 56 (pubertal) or 84 (early postpubertal) resulted in complete penile development. These findings suggest that early exposure of the penis to androgens in childhood may eventually result in a significant reduction of phallic size in adulthood.

McMahon DR, Kramer SA, & Husmann DA. (1995) Micropenis: does early treatment with testosterone do more harm than good?. The Journal of urology, 154(2 Pt 2), 825-9. PMID: 7609189

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