What is micropenis?

Micropenis is a medical term for a condition usually discovered in infants through a newborn examination. As the term suggests, micropenis refers to an abnormally small but normally structured penis. The condition is caused by hormonal or genetic abnormalities.

Important things to know about a micropenis:

  • Some men may believe they have a micropenis, but that’s likely not the case. It’s very rare.
  • A micropenis has a stretched penile length (SPL) of less than 2.5 standard deviation (SD) below the mean for the male’s age.
  • In men, an SPL of 3 2/3 inches or less indicates a micropenis. The average SPL for adult males is 5.25 inches.
  • Genetics (family history) may play a role in the condition.
  • There is no cure for micropenis but hormone therapy may be done for children to stimulate penile growth.

How common is micropenis?

Micropenis happens rarely. Estimates vary, but studies indicate 0.6 percent of men worldwide have the condition. In the years 1997-2000, 0.015 percent (1.5 in 10,000 births) of boys in the United States were born with micropenises.

What are the symptoms of micropenis?

The primary symptom of micropenis is a penis that measures less than 1.9 cm (0.75 inches) in length at infancy. The mean (average) stretched penile length for a newborn is 3.5 cm (1.4 inches).

Micropenis is diagnosed if the length is less than 2.5 standard deviation below the mean. In adult males micropenis is defined as a penis as 3 2/3 inches or less.

Micropenis may accompany other health problems due to hormonal disorders or congenital (present at birth) conditions, which can cause a variety of symptoms. Your child’s symptoms will depend on the cause of the micropenis.

What are the causes of micropenis?

Micropenis is usually caused by fetal testosterone deficiency which can be the result of a variety of conditions. The most common is hypogonadotropic hypogonadism.

Hypogonadotropic hypogonadism is a condition that occurs when the hypothalamus (the part of the brain that controls the autonomous nervous system and pituitary) does not secrete the hormones that stimulate the testicles to produce hormones (testosterone) necessary for normal maturation and reproductive function.

Micropenis may also be found with genetic syndromes that can cause other malformations. Or the condition may be idiopathic (have an unknown cause).

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy