What Is Considered a Micropenis?

Micropenis is an extremely rare condition that occurs in only 1.5 per 10,000 children in the United States. The term is used to describe a stretched, flaccid penis that is shorter than 3.66 inches.

Micropenis is the result of abnormal fetal development. Experts believe it is triggered by a genetic aberration or hormonal abnormalities.

This article discusses the symptoms, causes, and diagnosis of micropenis. It also covers the treatments available and ways to cope.

How Is Micropenis Diagnosed?

Micropenis occurs when the penis is abnormally small compared to other average-sized genital structures, including the scrotum, testicles, and perineum.

Micropenis is usually diagnosed at birth. In newborns, a healthcare provider must take a proper measurement of the baby's penis when diagnosing micropenis. They will measure the stretched penis length (SPL) 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 an SPL of less than 1.9 centimeters. For older people, it's characterized by a penis length that's 2.5 standard deviations (SD) smaller than the average for the age.

As a guideline, the Harriet Lane Handbook from John Hopkins University defines micropenis as follows:

The variations in average penis size from age 7 are due to the differences in development as people approach puberty. By puberty, it becomes far more difficult to define micropenis by centimeters alone. Mathematical calculations are needed until puberty is complete.

Differential Diagnosis

While the clinical definition of a micropenis seems to offer a definitive roadmap for diagnosis, that's not always the case. This is especially true in people over the age of 8.

Most prepubescent people brought in by their parents because of an underdeveloped penis rarely have a micropenis. In most cases, the person is either experiencing delayed puberty or obesity (obscuring the penis length with excessive pubic fat). Or he simply has a larger frame compared to an otherwise normal penis.

In cases like these, the term "inconspicuous penis" may be more appropriately applied. It may be secondary to congenital conditions such as penoscrotal webbing. This is a condition where the scrotum extends up the underside of the penis, creating an indistinct junction between the two.

Another possible diagnosis is a megaprepuce in which the foreskin cannot retract and balloons abnormally.

Causes

A micropenis develops during gestation or before the baby is born. It can have a number of causes. A few of these are outlined below.

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
• 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

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

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 a micropenis, circumcision should be delayed until the testosterone therapy is completed. Generally speaking, the therapy is most effective in children under 3 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, called a suspensory ligament release, 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.

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.

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.