Micropenis

What Is a Micropenis?

The term “micropenis” is often used incorrectly to refer to a penis on the smaller side of average. However, micropenis is a medical term that specifically refers to a penis that’s significantly smaller than normal due to disruptions in penile development during infancy or before birth. It’s also medically known as micro penile syndrome or microphallus.

Micropenis may develop due to to a number of conditions that cause hormonal disruptions early in life, when the male genitals develop.

Hormonal therapy during childhood can help support penile development for some children with micropenis. If medications aren’t effective, doctors sometimes consider surgery.

Read on to learn more about what micropenis is including why it develops, how small your penis needs to be to be considered micropenis, and potential treatment options.

How Common Is a Micropenis?

Micropenis is an incredibly rare condition describing an abnormally small penis that’s significantly below the average size for an individual’s age and developmental stage. It’s reported in about 3 per 20,000 male births.

Micropenis can occur as a result of genetic problems, hormonal disruptions in the womb, and other disruptions in normal genital development. It requires early diagnosis and treatment during childhood to prevent abnormal development throughout childhood and adolescence.

Micropenis Size: What Is Considered a Micropenis?

Although the term "micropenis" is often used casually to describe a small penis, it is in fact a medical term referring to a penis that is significantly smaller than average.

Micropenis is typically diagnosed when the stretched penile length is more than 2.5 standard deviations below the average size in context of age and ethnicity, measuring under 2.04 inches (5.2 cm) in flaccid length and less than 3.34 inches (8.5 cm) when stretched.

In research, stretched penis length is commonly measured instead of erect length because it closely approximates the same size without requiring sexual arousal. This method involves gently stretching the flaccid penis to its maximum comfortable length.

Standard deviation is a statistic that researchers use to examine how far an individual differs from the average in a sample. Being 2.5 standard deviations below average means you're measuring lower than almost everyone else, and about 99 out of 100 people would be higher than you.

How Big is a Micropenis?

Normally, the penis continues to grow during maturation through childhood and teenage years. People with micropenis may have limited growth during their developmental years.

Your child’s doctor will likely want to further evaluate your male newborn if their penis is under about 2 centimeters (0.8 inches).

Other suggested cut-off sizes for micropenis by age have been proposed as:

It’s important to remember that these sizes are coming from stretched penile length, which is generally similar to erect penile length for adults. These measurements are not coming from flaccid penis length.

Micropenis Symptoms

The characteristic sign of a micropenis is a penis much smaller than expected for your age. Micropenis usually doesn’t cause any specific symptoms, but certain conditions associated with micropenis might cause additional symptoms or complications.

A micropenis is typically identified during a physical exam shortly after birth or in early infancy. The primary sign of a micropenis is a noticeably small penis size. People with micropenis may have:

• Normal testes and scrotum size

• Normal urinary function

• Normal reproductive function

For some people with a micropenis, sexual intercourse is difficult. Specific sexual positions that allow the penis to penetrate more deeply may make intercourse easier.

It's important to understand that micropenis is not the same as a “buried penis.” These two are distinct conditions, even though they may appear similar at first glance. A buried penis refers to a normally sized penis that appears hidden or less visible, often because it is surrounded by excess fat or loose skin in the pubic area.

This is especially common in individuals with obesity. A buried penis is usually addressed through lifestyle changes such as weight loss and, in some cases, surgical correction.

Does Penis Size Matter?

Penis size is often a subject of concern among males. Pornography and other societal influences have largely distorted the perspective of what’s considered a normal penis size.

According to research, the average erect penis size is likely between 5.1 and 5.5 inches, and likely closer to the bottom end of this range when volunteer bias is taken into account.

One review published in the World Journal of Men’s Health in 2023 analyzed 75 studies spanning 79 years and including data from over 55,000 men. The researchers found that the average erect penis length was approximately 5.5 inches, leading them to conclude that this is the typical length for an erect penis.

While some women may have a preference for a larger penis size, most research suggests that men are often more preoccupied with penis size than women.

In an older 2002 study, among 375 sexually active women surveyed only 20 percent reported penis length as important and only 1 percent reported it as very important.

Learn more about penis size.

Causes of Micropenis

Micropenis often develops due to fetal testosterone deficiency in utero, which may lead to delayed or incomplete puberty. When the brain fails to release the hormones needed to tell the testicles to produce testosterone, normal sexual development, including penis growth, is disrupted.

Micropenis is also linked to some genetic conditions passed through families.

The male reproductive tract begins to develop during the end of the first trimester in the womb in response to hormones produced by the testicles, such as:

• Anti-Mullerian hormone

• Testosterone

• Dihydrotestosterone (DHT)

The hormones testosterone and DHT are known as androgens. Androgens are male sex hormones that help develop male sexual characteristics. Large surges in androgen levels in the second trimester normally accelerate penile growth.

After birth, additional development of the penis and other sexual characteristics develop under the influence of hormones produced by glands in your brain called your hypothalamus and pituitary gland.

These hormones include:

• Donadotropin-releasing hormone (GnRH)

• Follicle-stimulating hormone (FSH)

• Luteinizing hormone (LH)

Surges in these hormones 1–3 months after birth contribute to the further development of the penis.

Micropenis usually develops due to hormonal problems during one of these time periods. Sometimes, the cause is identifiable, whereas other times, it’s not, even after comprehensive testing. When no underlying cause can be found, it's called idiopathic micropenis.

Risk Factors for Micropenis

Micropenis has been linked to many different genetic syndromes and medical conditions that disrupt development of the penis early in life. Some of these conditions include the following:

Kallman syndrome

Kallman syndrome occurs in about 1 in 30,000 males and is characterized by problems with the neurons in your hypothalamus. Other signs can include:

• Hypogonadotropic hypogonadism, low testosterone due to problems with the hypothalamus or pituitary gland

• Osteoporosis

• Hearing impairment

• Lack of smell

Prader-Willi syndrome

Prader-Willi syndrome is a genetic condition that occurs in about 1 per 20,000 to 30,000 births. Signs can include:

• Poor muscle tone

• Obesity

• Intellectual disability

• Undescended testes

• Micropenis

• Small hands and feet

Klinefelter (XXY) syndrome

Klinefelter syndrome occurs when you have an extra X chromosome. It occurs in 1 in 500–1,000 male births and often isn’t recognized until adulthood. Klinefelter syndrome may also cause:

• Small testicles

• Infertility

• Enlarged breasts

• Poor coordination

• Reading difficulties

Other conditions

Other conditions linked to micropenis include:

• Growth hormone deficiency

• Hypopituitarism, low levels of pituitary hormones

• Androgen receptor defect or resistance

• Absence or improper formation of the testes

• 5 alpha-reductase deficiency

• Rare types of congenital adrenal hyperplasia

• Androgen insensitivity syndrome

Diagnosing Micropenis

The main way your child’s healthcare provider will diagnose micropenis is by measuring stretched penis length.

Many healthcare specialists, such as pediatric endocrinologists and pediatric urologists, might be involved in the diagnostic process for micropenis.

Diagnosis of micropenis involves several steps to ensure accurate identification and to rule out other conditions. The process includes:

• Physical examination. A thorough evaluation of penile length, structure, and overall genital anatomy is performed. Your doctor will also look for problems with the testicles. Measurements are compared to standardized growth charts for age. Stretched length is generally considered the most accurate measurement method.

• Medical history. Your child’s health, including family history, mother’s health during pregnancy, and developmental milestones, is documented in a detailed medical history.

• Hormonal testing. Blood tests may be conducted to assess levels of hormones such as testosterone, dihydrotestosterone, luteinizing hormone, and follicle-stimulating hormone (FSH).

• Imaging studies. A specialist in urology may order an ultrasound or MRI to look at your internal structures and help differentiate micropenis from other conditions such as buried penis, webbed penis, and trapped penis.

• Genetic testing. If a genetic condition is suspected, doctors will often order a blood test to look for genes linked to that genetic condition.

Treatment for Micropenis

If micropenis is identified early, it may be treatable with medications to increase your child’s level of androgen hormones.

Micropenis treatments depend on the underlying cause and the individual’s age. Options include:

• Hormone therapy. Testosterone therapy or other hormonal therapies, such as human chorionic gonadotropin, are commonly used in infancy or during puberty to stimulate penile growth. This approach is most effective when the condition results from hormonal deficiencies since the penis needs androgen hormones to grow. Testosterone treatment is unlikely to treat micropenis not linked to hormonal problems.

• Growth hormone therapy. In cases of growth hormone deficiency, growth hormone treatment may help improve overall growth, including penile development, and sexual function.

• Surgical interventions. For severe cases or when hormone therapy is ineffective, surgical procedures like phalloplasty can be considered to reconstruct or enhance the size of the penis. However, surgery is usually only reserved for serious cases. Surgery comes with a high risk of complications and dissatisfaction with the appearance of the penis.

• Psychological support. Counseling and support groups can help address the emotional and social challenges associated with micropenis.

• Delaying circumcision. Delaying circumcision is usually recommended in children receiving hormonal therapy until the treatment is complete since the penis may undergo rapid growth.

Micropenis Prevention

Micropenis is not preventable in adults once the penis is fully formed, but making sure your child receives regular check-ups with their pediatrician can help monitor their penile development.

Early recognition of micropenis is necessary to nurture the proper development of the penis throughout childhood and the teen years. If the penis hasn’t developed properly in childhood, there are limited treatment options in adulthood.

Some of the ways to help ensure your child’s penis and other aspects of their health develop properly include:

• Prenatal care. Prenatal care refers to regular checkups from doctors, nurses, or other health experts throughout pregnancy. Prenatal care helps ensure you avoid substances that might harm your child’s development and make sure your pregnancy is progressing as expected.

• Regular check-ups for your child. Making sure your child receives regular check-ups can help monitor their development. Pediatric doctors can help determine if there are any abnormalities in your child’s development.

• Early treatment. Early diagnosis and treatment of hormonal deficiencies in infants or young children can improve the development of their genitalia.

• Genetic counseling. Some genetic conditions caused by genes that run in families are linked to the development of micropenis. If you have a family history of a condition, such as Kallman syndrome or Klinefelter syndrome, it’s a good idea to consult a genetic counselor before conception to learn about the potential risks for your child.