Micropenis: Definition, Size, What A Microphallus Looks Like

Micropenis, or microphallus, is a medical term used for a penis abnormally smaller than the average length. 

A penis shorter than 0.75 inches at birth, or less than 3.67 inches in an adult male, is medically diagnosed as micropenis. 

Most people with micropenis can perform normal functions of the penis and rarely experience any issues related to erection and urination.  

Keep reading to learn more.

Signs of a micropenis

The significant sign of a micropenis is the smaller-than-average penis. The limited penile growth may change the scrotum position as it is located closer to the penile base. 

Micropenis can cause self-consciousness and low self-esteem that may lead to other psychological problems. 

Apart from the apparently shorter penis, there are no other common signs of micropenis. However, in some cases, people with micropenis may have a relatively low sperm count.

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What causes a micropenis?

Testosterone deficiency is the primary cause of micropenis in most cases, while the exact cause is unknown in some cases. 

Other underlying conditions leading to micropenis may include: 

  • Deficiency of growth hormone
  • Absence of testes
  • Hypoglycemia
  • Prader-Willi syndrome
  • Problems with androgen receptors

Diagnosing microphallus

Physical Examination

Micropenis is mainly diagnosed by physical examination of the penis that includes measuring stretched penile length (SPL). 

It is measured by gently stretching the penis, holding it close to the body, and measuring its distance from the tip to the base of the penis. 

Then, SPL is correlated with the standard deviation (SD) of the mean for the corresponding age. SPL values of less than 2.5 SD indicate micropenis.  

Age Lower Limit of Penis Size
Preterm infants born at 30 weeks of gestation1.5 cm
Preterm infants born at 34 weeks of gestation2 cm
Full term infants2.5 cm
One-year-old2.6 cm
Five-year-old3.5 cm
Ten-year-old3.8 cm
Adults9.3 cm

Imaging tests

Imaging tests such as pelvic ultrasound and MRI may be performed.

Lab tests

An endocrinological assessment is done to know the root cause of microphallus. DHT, serum gonadotropin, and testosterones are tested. Sometimes, other pituitary hormones can also be measured if needed.

Potential treatment options for micropenis

A few methods are available for the treatment of micropenis that can help increase the length of the penis. 

Some of these treatments are mentioned below, along with their limitations.

Testosterone therapy

Testosterone therapy can be provided if the micropenis is diagnosed at infancy and before puberty. 

This therapy is offered in three months to help the penis grow. Testosterone can be provided in the shape of shots, skin gel, or creams. 

An intramuscular testosterone ester for the short term is recommended to use. The dose of testosterone should be 25mg for 3-4 months and once in 3-4 weeks.

Topical DHT (Dihydrotestosterone)

DHT is a vigorous androgen and is adequate to treat PAIS (partial androgen insensitivity syndrome) or if testosterone conversion into DHT is not occurring. 

This helps develop the male genitalia and can increase the length of the penis. It also aids in treating low testosterone levels as an anabolic steroid medicine with an androgen hormone.


Phalloplasty can be performed in older adults or adolescents and is unsuitable for infants and young children. This is a surgical way to treat micropenis. 

If the hormone treatment didn’t work in infancy, then this procedure is an option. 

However, it also has associated complications, such as effects on erectile function or urinary tract issues. 

The surgeon selects the length of the penis according to phallus length, as it is available in different sizes.

Recombinant growth hormone

If the micropenis is only caused by growth hormone deficiency, then growth hormone intake can help increase the penile length. Supplements of androgen are not required. 

LH-FSH (Luteinizing hormone & Follicle stimulating hormone) treatment

If the recombinant LH-FSH treatment is given at early age of life, it helps promote the growth of testicles and increases penis length. 

Hypogonadotropic hypogonadism is usually treated with this method to increase penile length in children.

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What can be mistaken for a micropenis?

The following are a few conditions that can be mistaken as a micropenis.

  • A buried penis is average-sized but just hidden. This condition is generally diagnosed at the time of birth due to fat buildup in the abdomen and around the genitals. When the baby becomes a man, the pelvis muscles weaken, thus affecting erectile function.
  • A webbed penis is also known as an inconspicuous penis, which may occur by birth or due to circumcision complexities. Skin from the scrotum gets attached to the penis shaft. This masks the penis, and only the tip and some shafts are visible. 
  • Some males experience delayed penile growth. In such cases, the penis starts smaller but grows within the normal range with time.
  • In some males, psychological factors lead to the mistaken micropenis. Their perception of their body image and anxiety make them believe that they are suffering from micropenis; however, their penis ranges in average size.


What does a micropenis look like?

A micropenis looks significantly smaller than the normal penis; however, as there’s no structural abnormality in addition to a smaller size, the shape of a micropenis is the same as that of a normal penis.

How big is a micropenis?

The size of the penis depends upon the age of an individual. At birth, micropenis usually presents with a significantly smaller length of less than 0.75 inches, while the average size of the penis at birth is 1.4 inches. 

In an adult male, the stretched penile length (SPL) of micropenis is less than 3.67 inches, while the average SPL in adults is 5.25 inches. 

How common is micropenis?

The prevalence of micropenis is rare, affecting only 0.6% of males globally. In the US newborns, its incidence is 3 in 20,000 newborn males. 

Does a micropenis affect sexual function?

Micropenis usually does not cause problems in sexual activity, and males with a micropenis can reach orgasm with the same ease as an average-sized penis.

However, anxiety due to lack of self-acceptance may cause less pleasure and early ejaculation during intimacy.  

Sometimes, a micro penis may be linked with low sperm count, affecting fertility. People can still enjoy sexual intercourse with their partner as mostly all the nerves on the tips of the penis are fully functioning, which provides a pleasurable sensation.


A micropenis is a rare, congenital condition that is usually diagnosed at the time of birth. Micropenis occurs due to hormonal deficiencies, genetic abnormalities, or interaction with a chemical such as pesticides. 

Micropenis doesn’t usually affect sexual intercourse or urination, but in some cases, it may lead to lower sperm counts or affect fertility. 

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  1. Khadilkar, V., Mondkar, S.A. Micropenis. Indian J Pediatr 90, 598–604. 2023.
  2. Bin-Abbas B, Conte FA, Grumbach MM, Kaplan SL. Congenital hypogonadotropic hypogonadism and micropenis: effect of testosterone treatment on adult penile size why sex reversal is not indicated. J Pediatr. 1999 May;134(5):579-83. doi: 10.1016/s0022-3476(99)70244-1. PMID: 10228293.
  3. World Population Review. Penis Size by Country 2023.

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