What Is Micro Penile Syndrome

What is Micro Penile Syndrome?
Micro penile syndrome or micropenis is a medical term for an abnormally small but normally structured penis. Typically diagnosed in infants during a newborn examination, hormonal or genetic conditions can cause micro penile syndrome.  When diagnosing a micropenis, the standard measurement technique is to stretch the penis and measure the stretched penile length (SPL). A measurement of less than 2.5 standard deviations (SD) from the average for a man’s age suggests micro penile syndrome. The average stretched penis length (SPL) for an adult is 5.25 inches; a man with micro penile syndrome may have an SPL of 3.66 inches or less. 

Micro Penile Syndrome: How Common Is It?

While many men may believe they have a micropenis, the condition is very rare. Clinical estimates vary, but studies have suggested that 0.6% of men worldwide have micro penile syndrome. Between 1997 – 2000, 1.5 in 10,000 births (0.015%) of boys in the US were born with the syndrome. 

What Are the Symptoms of a Micropenis?

The most common symptom of micro penile syndrome is penis size. When a newborn’s penis is stretched gently, the SPL will be shorter than 0.75 inches.  Having a micropenis will not cause any other symptoms itself. However, as it often accompanies other health conditions due to hormonal or congenital disorders, other symptoms may present themselves.

Micropenis Causes

As previously mentioned, hormones or genetic conditions usually cause micro penile syndrome. Some of the most common include fetal testosterone deficiency and hypogonadotropic hypogonadism. Hypogonadotropic hypogonadism occurs when the hypothalamus (a part of the brain that controls the nervous system and the pituitary gland) doesn’t secrete hormones correctly to stimulate the testicles to produce testosterone, which is necessary for standard reproduction function and growth.  Alternatively, genetic conditions like the ones below can cause micro penile syndrome:
  • Testicular dysgenesis
  • Defects in testosterone synthesis
  • Androgen resistance deficiency
  • Androgen insensitivity
  • Growth hormone (GH) deficiency. 
There may not be any obvious or known cause for the condition in many instances. 

How Is Micropenis Diagnosed?

Usually, micropenis will be identified and diagnosed in infancy or childhood and revealed through a gently stretched penis measurement. This measurement is then compared to the average size for their age. From here, a diagnostic plan will follow to determine the best course of treatment and if it will be possible to stimulate penis growth. 

How to Treat a Micropenis

There is no cure for micro penile syndrome; however, certain therapies may help stimulate penis growth. The chances of penile growth are greater when diagnosed and treatment started in infancy.  There are two main types of treatment for micro penile syndrome, but it’s important to note the cause of the syndrome will impact the treatment outcome. Every child is different; the sooner treatment begins, the better the chances of success. 

Testosterone Treatment

In many instances, the first treatment for a micropenis will be a short course of testosterone, as this tests the ability of the penis to respond to growth hormones. Testosterone will be injected or applied to the groin topically in the form of a gel or ointment. Studies have shown that many infants respond well to testosterone treatment and penile growth occurs but whether the growth continues through puberty and into adulthood is unknown. 


Generally considered a last resort when medical treatments aren’t successful for children, surgery for a micropenis is a possibility. Phalloplasty (surgical reconstruction) of a micropenis for younger children can be complicated and risky, although it’s more common for young adults and adults.  If you’re considering surgery for your micropenis, it’s essential to understand the benefits and risks of surgery. 

What Should I Do If I Have a Micropenis?

In many instances, with early intervention and treatment, boys with micro penile syndrome due to hormone deficiency have a good prognosis. Typically, they will respond well to testosterone therapy with adequate penile growth (although below average size) and have full sexual function without complication.  However, if the micropenis is caused by a condition such as an androgen insensitivity, which will not respond to testosterone therapy, there are limited treatment options.  But it’s important to note that regardless of the treatment available, while a person with micropenis may not have an average-sized penis, this typically won’t impact sexual function, and even with a smaller-than-average penis, you can still have an active and healthy sex life.  If treatment for a micropenis has been unsuccessful or you need support living with a rare health condition, your doctor or primary healthy physician may recommend emotional and mental health support.   At Opt Health, we have specialized men’s health doctors who are available 24/7 and can provide treatment and test results from the comfort of your home. In addition to increasing men’s vitality, we use preventative medicine to help you feel like you again. Don’t hesitate to contact us if you have any questions or would like to book an appointment. 

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