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Micro Penis

Very small penis size


Updated May 16, 2014

Definition of Micro penis- A very small penis
Micropenis, also known as microphallus, is a penis that is 2.5 standard deviations below the mean (average) for the age and race of the child. This definition translates to a stretched penis length of less than 1.9cm (3/4 inch) long at birth and can be described as a micropenis. Statistically, micropenis occurs in 0.6% of the population.

Lack of development of sexual organs and penis size
There are many reasons why the penis may not develop. Very early in the development of the human male or female fetus differences in the genitalia cannot be detected, even though the sex chromosomes XX (in most females) and XY (in most males) have put down the basic building blocks. It is hormones produced by the gonads determined by the sex chromosomes that then determine which organs develop and which ones disappear. The same tissue that forms the clitoris in the female forms into a penis in males, the tissue that makes the scrotum in the male makes the labia in the female. Because of the complexity of fetal development things can and do go wrong. Therefore it should be no surprise that things can go wrong in the development of the sex organs.

Getting the best advice about micropenis
As a parent, advice and treatment options should be discussed with a specialist medical team made up of pediatricians, urologists, endocrinologists, geneticists and radiologists very soon after the birth of the child. Tests will need to be carried out to see if the gender of the baby can be determined. Treatment and management options need to be discussed that result in the best possible outcome for the child. The family need to be supported and informed. Changes in the way micropenis is treated by the medical expert’s means that it is worth getting more that one opinion to make sure all avenues have been explored if the treatment is complex or has lasting implications for the infant.

Causes of micropenis- very small penis
The central role here is chromosomes and hormones as the deciding factors of the male or femaleness of the fetus and baby. Micropenis occurs when these systems fail to work properly. There are many different possible causes and problems with penis growth can start the after 14 weeks of fetal growth.

Micropenis is often due to inadequate testosterone in 2nd and 3rd trimester of fetal growth. There may be a genetic cause. Although there is no gene per se that causes micro penis, there are a number of associated syndromes. An example is androgen insensitivity, where the fetus started as a male but was insensitive to testosterone (the male hormone), or syndromes caused by chromosomal abnormalities such as Klinefelter’s Syndrome, Turner’s Syndrome or Down’s Syndrome.The medical team can investigate the many possible causes and carry out tests that will inform future management and treatment.

Treatment for micropenis

  • Testosterone stimulation may be tried if the cause is hormonal. If the penis grows during a three month trial then a normal penis size and function can result.

  • Surgical reconstruction and hormone treatment could also be an option.
  • Gender assignment with no surgery to change the anatomy or gender reassignment may be considered.

  • Genetic syndromes will dictate treatment outcomes to a degree.

  • Psychological counseling and support for the family and child should be part of a good medical treatment program.
  • People who have experience of intersex issue feel strongly that reassignment should only happen when the child is old enough to make an informed choice themselves. It is for these reasons and because the treatment can have such profound results that a second medical opinion may well be helpful.

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