Question:

My son is 10 years old and he is concerned that his penis is too small. He has noticed that his is even smaller than his younger brother’s and he is self-conscious about sleepovers and being in change rooms with his peers. Is this a real concern, and if so, what medical treatment might be available to help him?

Answer:

True so-called micropenis or microphallus is a very rare condition. Typically it presents in the immediate newborn period rather than in adolescence. Micropenis is defined as a normal functioning penis but the size is 2.5 standard deviations below what one expects at that age. Microphallus usually refers to an associated issue such as hypospadias.

Hypospadias is an abnormality of the opening of the passage where urine flows called the anterior urethra. The urethral opening is located on top of the penis just proximal to the tip of the glans penis, which, in this condition, is spread open. The urethral opening may be located as far down as the scrotum or lower. The penis is more likely to have associated shortening and curvature.

The mean stretched penile length in a full-term newborn male is 3.5 cm. Less than 2.5 cm in a full-term newborn meets the definition of micropenis and warrants evaluation.

A true micropenis or microphallus can be present with other genetic abnormalities. However, a normal scrotum and testicles means more than likely that everything is fine.

In the first few years, the penis grows very little until puberty when testosterone levels begin to rise. Since your child is 10, he likely has not yet hit puberty and testosterone is going to impact his growth and development.

The urologists tell me that on occasion older boys are brought for evaluation because of concerns of small genitalia. Usually these boys have not hit puberty and sometimes are overweight. When you examine them, they in fact do have normal penis size based on stretched penile length, and the apparent smallness is secondary to the penis being concealed in the fat pad just above—the so called suprapubic fat pad.

Take your concerns to your son’s primary care physician. If there is a shared concern—which likely would have been voiced before now—a referral either to an endocrinologist to exclude any underlying medical causes or to a paediatric urologist can be helpful.

Originally published in 2012.