Definition

Micropenis is a medical term referring to a condition where the size of the penis is abnormally small, typically observed in babies or early childhood. Despite its small size, a micropenis typically has a normal anatomical structure.

Causes

Micropenis can result from hormonal disorders or genetic factors (hereditary). Hormonal issues, particularly a deficiency of testosterone hormone in the fetus, are the most common cause of micropenis. This deficiency often stems from conditions such as hypogonadotropic hypogonadism, where the hypothalamus fails to produce hormones that stimulate the testes to produce testosterone, crucial for normal maturation and reproductive function. Consequently, male fetuses do not produce sufficient testosterone.

Furthermore, testosterone deficiency can occur if the mother does not produce enough pregnancy hormone called hCG (human chorionic gonadotropin) during pregnancy. hCG stimulates testosterone development in the fetus. Additionally, despite normal testosterone levels, some medical conditions can inhibit the body's response to testosterone, a condition known as androgen insensitivity.

During the first three months after birth, male infants undergo a rapid increase in testosterone levels, critical for penis growth. Disruption of this process due to hormonal problems can result in a smaller penis at birth.

Micropenis can also be associated with genetic syndromes that cause other malformations, including:

• Prader-Willi syndrome
• Kallmann syndrome
• Growth hormone deficiency
• Chromosomal abnormalities
• Laurence-Moon-Bardet-Biedl syndrome

Sometimes, micropenis occurs without a known cause.

Risk factor

Micropenis and other congenital anomalies may be associated with environmental factors, including maternal exposure to pesticides or toxic chemicals during pregnancy. Consequently, this condition may be more prevalent in specific populations.

Symptoms

The normal and micropenis sizes are as follows:

• In babies, the average erect penis length ranges from 2.8 to 4.2 cm. A length of less than 1.9 cm is considered micropenis.
• In prepubescent boys, the average erect penis length is approximately 6.3 cm. A length of 3.8 cm or less is considered micropenis.
• In adult men, the average erect penis length is around 13.24 cm. Adults with micropenis have an erect penis length of 9.2 cm or less.

Micropenis can occur as a symptom of other medical problems, often due to hormonal disorders or congenital conditions, which may present with varying symptoms. Consequently, other symptoms may appear depending on the underlying causes.

At times, what initially appears to be a micropenis may actually be another condition. For instance, a baby born with swollen testicles may give the impression of having a micropenis. Additionally, the penis may appear less visible or buried due to surrounding fat, a condition known as buried penis, which is commonly seen in individuals with obesity.

It's important to note that most people with micropenis have normal sexual function. Micropenis typically does not affect a person's ability to urinate, masturbate, or achieve orgasm. However, some individuals may experience difficulty urinating while standing.

Diagnosis

Micropenis is diagnosed through a physical examination, usually conducted at birth or in young children, by measuring the length of the penis. The doctor fully stretches the penis and measures its length using a ruler or caliper. This measurement is then compared to the normal range of sizes for the child's age.

In addition to referencing the average erect penis length, micropenis can also be diagnosed if the erect penis length falls below 2.5 standard deviations below the average.

If a newborn baby's penis is abnormally small, the doctor may conduct examinations to assess the cause and determine appropriate therapy to stimulate growth. These examinations may include:

• Physical examination: In addition to measuring the penis, the doctor may look for other signs, such as fat accumulation or lumps around the penis.
• Blood test : Help the doctor check the baby's hormone levels. Genetic testing may also be performed to determine the baby's biological sex. In rare cases, babies with micropenis may be intersex or have sex chromosome abnormalities.
• Imaging examinations: The doctor may use imaging examinations, such as ultrasonography and/or MRI of the pelvis, to examine the genitals and surrounding structures.

Management

There is no known cure for micropenis. However, management aims to increase the size of the penis to ensure good functional development and enhance self-confidence. The specific therapy depends on the underlying cause and may vary from case to case. Initiating therapy during infancy or early childhood is crucial to optimize outcomes.

• Hormonal therapy: The initial treatment typically involves short-term testosterone hormone therapy. Testosterone can be administered through injections or applied as gel or cream to the penile area. This therapy is more effective when initiated before puberty compared to afterward. Research suggests that many infants show significant penis growth with testosterone therapy, although it's uncertain whether growth will continue during puberty. The therapy aims to assess the penis's response to growth hormones, with an increase in length by 100% considered a good response, while a response of 3.5 cm or more is considered sufficient. If testosterone therapy fails to increase penis length, other hormonal therapies may be attempted.
• Surgery: Surgery is considered only if medical therapy proves ineffective. Surgical reconstruction, known as phalloplasty, for young children with micropenis, is a complex and risky procedure. If considering surgery for micropenis, it's important to understand the risks and benefits in your individual situation fully.

The prognosis for males with micropenis can be worse in cases where other conditions, such as androgen insensitivity, are present. These conditions may not respond to hormone therapy, resulting in the penis remaining small despite treatment efforts.

Micropenis is a rare condition, and its management depends on various factors. Your doctor will assist you in making informed decisions, whether you're a parent of a child with micropenis or an individual seeking treatment.

Complications

If early micropenis therapy proves unsuccessful, it can be challenging for the patient and their family to accept this condition. Consequently, micropenis can lead to psychological problems. Anxiety about penis size may serve as a barrier to enjoying intimate relationships with partners. Despite undergoing therapy, men may still experience dissatisfaction with their appearance, even though they have normal sexual function.

Prevention

There is currently no known way to prevent micropenis.

When to see a doctor?

Many people may worry about having a smaller-than-normal penis size. If you suspect that you or your child may have micropenis, it's essential to consult with a doctor who is capable of accurately measuring and diagnosing this condition. However, it's important to note that doctors typically diagnose micropenis at birth.

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