A micropenis is a stretched penis length that is significantly smaller than average. The condition is uncommon and is due to genetic causes or hormonal conditions in the developing infant.

Micropenis is typically diagnosed at birth and often suggests an underlying endocrine (hormone) issue. Various treatment options are available depending on the cause.

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Definition of a Micropenis

A micropenis is a stretched penis length that is significantly smaller than the average penis size for a person's age.

For example, a full-term infant's average penile length is 1.1 to 1.65 inches (2.8 to 4.2 centimeters (cm)) long. A micropenis in an infant is considered when the penis is significantly less than the average length, at 0.75 inches (1.9 cm) long. It is a rare condition seen in approximately 1.5 per 10,000 children in the United States.

In adults, a micropenis is considered a stretched, flaccid penis that is 3.67 inches or less (9.32 cm). This contrasts with an average length of 4.72 to 5.87 inches (12 to 14.9 cm).

Diagnosis

Micropenis occurs when the penis is abnormally small compared to other average-sized genital structures, including the scrotum, testicles, and perineum. This is typically noticed and diagnosed at birth.

To diagnose a micropenis, a healthcare provider will measure the stretched penis length rather than flaccid or loose. This more closely correlates to the erect penis length in people.

For full-term newborns, a micropenis is defined as a stretched penis length of less than 0.75 inches (1.9 cm). Penile size changes as an individual grows. If an individual's penis is significantly smaller than the average for their age, then it may be a micropenis.

Penile lengths suggestive of a micropenis are in the chart below.

Stretched Penis Lengths by Age Suggestive of a Micropenis
Age	Length
0 to 5 months	Less than 0.75 inches (1.9 cm)
6 to 12 months	Less than 0.9 inches (2.3 cm)
1 to 2 years	Less than 1.02 inches (2.6 cm)
2 to 3 years	Less than 1.14 inches (2.9 cm)
3 to 4 years	Less than 1.3 inches (3.3 cm)
4 to 5 years	Less than 1.38 inches (3.5 cm)
5 to 6 years	Less than 1.5 inches (3.8 cm)
6 to 7 years	Less than 1.54 inches (3.9 cm)
7 to 8 years	Less than 1.46 inches (3.7 cm)
8 to 9 years	Less than 1.5 inches (3.8 cm)
9 to 10 years	Less than 1.5 inches (3.8 cm)
10 to 11 years	Less than 1.46 inches (3.7 cm)
Adult	Less than 3.66 inches (9.3 cm)

In contrast, the average infant penis is 1.54 +/- 0.3 inches (3.9 +/- 0.8 cm); the average adolescent penis is 2.52 +/- 0.43 inches (6.4 +/- 1.1 cm); and the average adult penis is 5.24 +/- 0.63 inches (13.3 +/- 1.6 cm).

There is a lot of variation in penile size during puberty, which makes it challenging to diagnose a micropenis by centimeters alone. Mathematical calculations are usually needed until puberty is complete.

Does Height Affect Penis Size?

Studies have not found any correlation between penis size and height in people without underlying medical conditions.

Causes

A micropenis is the result of abnormal fetal development and develops during gestation before the baby is born. Genetic or hormonal conditions may trigger the condition. While the majority of micropenises function appropriately, they are often indicative of an underlying health condition.

A workup with an endocrinologist can provide information about the cause and appropriate treatment options. Several different causes are possible.

Hormone Deficiency

Micropenis can be related to problems with the pituitary gland, which produces hormones, or the hypothalamus, which controls the pituitary gland. Abnormal levels of hormones that affect the growth of sex organs can cause the penis to be underdeveloped.

Micropenis can also be caused by a condition called fetal testosterone deficiency. One of the possible causes of this is the low production of human chorionic gonadotropin (hCG) during the early part of the pregnancy. This is a hormone that stimulates the developing testes to produce testosterone.

After 14 weeks, the growth of the penis falls under the influence of another hormone, known as luteinizing hormone (LH). LH also stimulates testosterone in the so-called Leydig cells of the testicles. If the production of LH or testosterone is blocked, the child's penis length may be affected.

Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is a genetic condition that causes small stature and behavioral and mental abnormalities. People with PWS have multiple hormone deficiencies including growth hormone deficiency, central adrenal insufficiency, hypogonadism, and hypothyroidism. Micropenis is common in people with this condition.

Prader-Willi syndrome can be treated with growth hormone therapy and other interventions such as physical and behavioral therapy. Growth hormone therapy is most successful when started early in life.

Genetic Conditions

Genetics may also play a role. While there is no single gene that causes micropenis, the condition is commonly linked to such chromosomal disorders as:

Androgen insensitivity syndrome (AIS): A condition that causes the body to be resistant to androgens (male sex hormones)
Klinefelter syndrome: A condition caused by an extra X chromosome
Down syndrome: A condition with a third copy of chromosome 21

Fertility Medications

There is also evidence that estrogen-based fertility drugs like diethylstilbestrol (DES) may cause smaller-than-normal penis size if taken during early pregnancy.

Environmental Exposure

Environmental pollutants are a less common cause, but some research suggests that exposure to chlorinated pesticides during pregnancy may cause micropenis and other genital abnormalities in babies.

Other Causes of a Small Penis

Most prepubescent people brought in by their parents because of an underdeveloped penis rarely have a micropenis, and there are several other explanations. Reasons someone's penis may appear small include, but are not limited to:

Delayed puberty: The average age for puberty in boys is between 9 and 14 years old. However, sometimes puberty is delayed, and the body will naturally go into puberty, or there is an underlying hormonal cause.
Obesity: Obesity can obscure the penis, especially if there is excess pubic fat, making the penis appear smaller.
Larger frame: In those with a larger frame, their penis may look smaller compared to someone of an average height, yet be a perfectly normal length.
Webbed penis: This is a congenital condition where the scrotum extends up the underside of the penis, creating an indistinct junction between the two.
Megaprepuce: In this condition, the foreskin cannot retract and balloons abnormally.

Complications

Micropenis is associated with problems with fertility as well as emotional and psychological issues.

Fertility

A penis length of fewer than 2 inches is associated with a lower likelihood of conception. Moreover, some people with a micropenis will have a low sperm count as a result of an underlying pituitary disorder.

In such cases, assisted reproductive techniques are available to significantly improve one's chances of conceiving.

Urination Problems

From a practical standpoint, a micropenis may complicate urination by making it difficult to direct the stream. Many people will simply compensate for this by sitting on the toilet when urinating.

Emotional Well-Being

While there are treatments that may enhance penis size, the reality is that some individuals will have a smaller-than-normal penis. Some people assume that this will cause inherent psychological harm. However, those beliefs are more reflective of our cultural attitudes about penis size rather than the person's individual experience.

Long-term research shows that people with micropenises have similar masculine self-images as people of average or above-average penis size.

Treatment

The treatment of micropenis will vary between children and adults. The goals remain the same: preserve the ability to take part in sexual activity and maintain the ability to urinate while standing. Treatments include medical and surgical options, often under the care of a multidisciplinary medical team.

Depending on the treatment plan, the medical team may include a pediatrician, urologist, endocrinologist, geneticist, or psychologist.

Testosterone Therapy

A micropenis can be treated in infants and children with 25 mg intramuscular (IM) injections of testosterone. These injections may increase penis size to the appropriate age range. The shots are given in 21-day intervals.

For a baby with micropenis, circumcision should be delayed until the testosterone therapy is completed. Generally speaking, the therapy is most effective in children under 3 years of age but may benefit people up to the age of 8.

Gender Reassignment

Gender reassignment surgery is a controversial treatment that was once recommended for children with micropenis. This was more in response to a general cultural discomfort with small penis size rather than a real medical need.

Today, gender reassignment surgery is no longer recommended. There is no evidence that it has any clinical, physical, or psychological benefits for people with micropenis.

Penis Enlargement Surgery

Some people with micropenis will opt to undergo penis enlargement surgery (phalloplasty) with varying degrees of success. One such operation is called a suspensory ligament release, which involves the detachment of the ligament that supports the penis during an erection.

Doing so allows the penis to lie at an obtuse angle (between 90 and 180 degrees) rather than an acute angle (less than 90 degrees), creating the perception of greater length. Potential risks include nerve damage, loss of penile sensation, and erectile dysfunction. It could also lead to the retraction of the penis if scar tissue develops at the incision site.

Other forms of phalloplasty, such as flap surgery (grafting skin from another of the body), are less commonly pursued. That's because they carry a considerable risk of complications and may interfere with sexual function.

Other techniques are more likely to increase the girth rather than the length of the penis. These include silicone implants (prostheses), synthetic dermal fillers, and subcutaneous fat injections. Even if length gains are achieved, it would only affect the flaccid length. The erect length would remain the same.

There are also commercially marketed penis pumps and stretchers that have not demonstrated consistent results in delivering gains in penis length. If achieved, they tend to be modest at best. These devices are intended for those with erectile dysfunction—an entirely separate concern.

Outlook

The outlook for a micropenis depends on the cause and response to treatment. For example, androgen insensitivity syndrome is challenging to treat. In contrast, infants with fetal testosterone deficiency who need testosterone supplementation often respond well to treatment and may go on to develop an average-sized penis.

Coping

A micropenis doesn't interfere with a man's libido, sexual function, sexual satisfaction, erection ability, or capability for mutually gratifying sexual relationships.

However, many people with micropenis experience emotional distress. In these cases, consultation with a therapist can help with mental and emotional well-being.

It can be difficult to talk about micropenis with a potential partner. Approaching the subject will depend on the specific situation and the expectations between you and your partner.

Many people with micropenis try to talk about it with their partner before initiating sexual contact. This can help set expectations and also allow you to discuss all the potential ways that a sexual relationship can be gratifying for both partners.

Small Penis Syndrome

Some individuals may feel they have a small penis, even if their penis is not considered a micropenis. Small penis syndrome is a recognized body dysmorphic disorder (BDD).

While not considered a micropenis complication since individuals with small penis syndrome technically do not have a micropenis, it is a related condition that warrants medical care. Individuals with a BDD diagnosis have higher rates of suicide than the general population. Treatment is available for this condition.

How to Measure Your Own Penis

If you are concerned that you have a micropenis or wondering how your penis compares to the average for your age group, it is possible to measure your penis at home.

Penile measurements are most accurate on a non-erect penis. Stretched penis length is done by measuring from where the penis connects to the pubic bone to the distal tip (the end part of the penis farthest away from your body). You can use a ruler or tape measurer to measure the length.

The average stretched penis length in an adult male is 5.24 +/- 0.5 inches (13.3 +/- 1.6 cm).

Summary

Micropenis is a rare condition that's the result of abnormal fetal development. It can be due to genetic conditions or low hormone production. Healthcare providers will measure a newborn baby's penis to help diagnose the condition.

Early detection is important for effective treatment, which may include testosterone therapy.

22 Sources

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