What is Micropenis?
Micropenis is a condition diagnosed through precise measurements of the penis length. Since this could lead to significant anxiety, stress, and psychological issues, it’s crucial to diagnose this accurately. Once diagnosed, a team of various healthcare professionals should handle the treatment of a micropenis. This condition can occur on its own or as part of other symptoms that hint at imbalances in hormones or related genetic factors.
What Causes Micropenis?
When a baby is conceived, it’s either given XX chromosomes to become female, or XY chromosomes to become male. Early on while the baby is still growing in the womb, it has both male and female reproductive ducts. The presence or absence of a gene, called the SRY gene (located on the Y chromosome), decides whether male or female organs develop. This gene prompts testicular development if present. At this early stage, the developing testes release three crucial hormones:
* Anti-Mullerian hormone (AMH): This hormone stops the female reproductive ducts from developing
* Testosterone: This hormone makes the male reproductive ducts grow into structures like the seminal vesicle (which holds semen), vas deference (a tube that carries sperm), and epididymis (a tube where sperm matures)
* Dihydrotestosterone (DHT): This hormone helps male sexual characteristics like a scrotal sac, penis, and testicles grow and mature.
With the help of these hormones, male reproductive and urinary systems start to develop between the 8th and 12th week of gestation (pregnancy). Another hormone called human chorionic gonadotropin (hCG) helps the Leydig cells to make testosterone. This testosterone is then converted to DHT. The presence of high levels of these hormones in the second trimester encourages the growth of the penis. After birth, the further development of male sexual characteristics is controlled by hormones regulated by parts of the brain called the hypothalamic-pituitary axis. The highest levels of these hormones are usually between the first and third months of life.
Undervirilization (insufficient male characteristics) and micropenis (an unusually small penis) are usually caused by any interruption in these steps. This can happen because of several reasons such as:
* Kallman syndrome: characterized by a lack of sex hormone, fragile bones, hearing loss, and an impaired sense of smell
* Hypopituitarism: characterized by low blood sugar, interruption of sex hormone production, and growth issues
* Prader Willi syndrome: characterized by reduced muscle tone, obesity, intellectual disability, undescended testes, small penis, small hands and feet
* Growth hormone deficiency
* Defect or resistance of androgen receptor
* Anorchia: absence of testes
* Klinefelter syndrome: characterized by small testicles, infertility, development of breasts in men, poor coordination, and reading difficulties
* Genetic disorders such as Trisomies of the chromosomes 8,13,18, and 21
* Noonan syndrome: characterized by wide-set eyes, a short neck, low set ears, skeletal abnormalities, bleeding disorders, and a heart issue called pulmonary valve stenosis
* Improper development of the ovary or testes
* 5 alpha-reductase deficiency: the body can’t change testosterone into DHT
* Rare types of congenital adrenal hyperplasia: a problem in making hormones that help the body to maintain proper glucose and electrolyte levels, and to regulate the immune system
In some cases, the reason behind this remains unclear.
Risk Factors and Frequency for Micropenis
Micropenis is not a common condition, affecting only about 1.5 in every 10,000 newborn boys in North America. Some research suggests that there might be minor variations in average penis length among newborns of different races. On average, white newborns have a penis length of 2.6 cm, East Indian newborns have a length of 2.5 cm, and Chinese newborns have a length of 2.3 cm. Other studies have come up with specific average penis length standards for babies and children in Brazil, Japan, and Turkey.
Signs and Symptoms of Micropenis
Diagnosing a micropenis requires a detailed medical history and physical examination. After diagnosis, it’s important to identify any related abnormalities and understand their causes.
A detailed maternal history is the initial step in assessing for micropenis. A history of consanguinity and ambiguous genitalia can suggest inherited conditions. It’s also important to ask about any medications the mother took during pregnancy, as certain anti-androgen medications can affect male genital development before birth.
The physical examination is a vital part of evaluating a micropenis. Signs of underdevelopment associated with low blood pressure and a fast heart rate can indicate problems with the adrenal glands relating to rare forms of a condition known as congenital adrenal hyperplasia (CAH). It’s crucial to accurately measure the length of the penis. The penis shaft should be fully stretched, and the distance is measured from the pubic bone (after pressing the fat above it) to the tip of the penis (with the foreskin retracted as much as possible). Taking an average of multiple measurements can ensure accuracy.
A penis length less than two and a half standard deviations below the average for the corresponding age confirms the diagnosis. Here are the suggested lower limits of penis lengths in centimeters according to age:
- Preterm infants born at 30 weeks of gestation: 1.5 cm
- Preterm infants born at 34 weeks of gestation: 2 cm
- Term infants: 2.5 cm
- One-year-olds: 2.6 cm
- Five-year-olds: 3.5 cm
- Ten-year-olds: 3.8 cm
- Adults: 9.3 cm
Another essential step in the evaluation is the thorough examination of the testicles. Other aspects to look for include the appearance and maturity of the scrotal sac, the location of the urethral opening, the curvature of the penis, and any other unusual features.
Testing for Micropenis
If the doctor suspects that you have a micropenis (a smaller than average penis), there will be a series of tests necessary to figure out the cause and to develop an appropriate treatment strategy.
These tests usually include:
- Measurement of various hormone levels, such as testosterone, DHT, luteinizing hormone (LH), and follicle-stimulating hormone (FSH).
- A test to evaluate the function of the testes. This involves measuring your testosterone level before and after you’re given a medication called hCG. If your testosterone levels remain below 300 ng/dL even after hCG administration, this suggests that your testes aren’t functioning as they should.
- Specific tests to rule out rare conditions linked with male under-development. These tests involve checking the levels of progesterone, 17-OH progesterone, androstenedione, and 17-OH pregnenolone.
- An ultrasound of your pelvis. This painless test utilizes sound waves to create images of your body, allowing the doctor to check your internal reproductive organs.
- An MRI of your brain. This test uses a strong magnetic field and radio waves to create detailed images of your brain regions, specifically, the pituitary gland. The pituitary gland is a tiny organ at the base of your brain that controls hormone production, including those involved in sexual development.
All these tests help your doctor to get a comprehensive understanding of your condition, and suggest appropriate treatment options tailored to your specific needs.
Treatment Options for Micropenis
The aim of managing micropenis is to:
1. Reduce the social stigma associated with it
2. Ensure normal sexual function
3. Ensure typical urinary function when standing
Both medical and surgical treatments have shown varying levels of success. The choice of treatment generally depends on the main cause, the age when the condition is identified, the level of shrinkage, and what the patient hopes to achieve from treatment. It’s usually best to try medicinal treatment first, and then consider surgical options if the medicinal approach doesn’t offer the desired results.
Medicinal Treatment
Testosterone can be obtained as an injection into the muscle or a cream that is applied to the skin. A study on using a 5% testosterone cream on children and infants under eight years old showed promising results, with 90% of patients achieving a significant increase in penis length and testosterone levels in their blood after 30 days of use.
Dihydrotestosterone (DHT), which is a form of testosterone, has shown promising outcomes, especially in infants with 5-alpha reductase deficiency. Human recombinant FSH and LH could be an option for children with hypogonadotropic hypogonadism, a condition that results in low levels of the male hormones needed for sexual development.
Surgical Treatment
A penis reconstruction surgery may be considered if medical treatment does not give satisfactory results. While surgical treatment can often produce acceptable results, many patients who have undergone the procedure continue to be unhappy with the appearance of their penis.
What else can Micropenis be?
It is critical to rule out a condition called pseudo micropenis when examining for certain medical conditions. In pseudo micropenis, the penis might seem small due to the surrounding tissues being more noticeable or because the penis is attached to the skin below it. A thorough and meticulous physical examination is necessary to discern this, helping to prevent unnecessary invasive testing and the associated stress for the patient and their family. Another condition, referred to as Chordee of the penis, results in an unusually bent penis, which can make the penis appear shorter than it really is.
