1. What is Micropenis?
  2. What are the causes of Micropenis?;
  3. How is Micropenis diagnosed?
  4. What is the treatment of Micropenis?

What is Micropenis?

Micropenis, or Microphallus, is defined as an erectile penile length of less than 2,5 standard deviations (SDs) below the mean for age penile size. 

In full-term neonates, the mean penile length is 3,5cm. When penile length in the newborn is less than 2-2,5cm (i.e. 2,5 SDs below the mean value), this condition is considered to be Micropenis. Mean penile length is related to age, and there are special tables presenting mean penile size standards according to age. The most classical and widely used is the Feldmann and Smith Table, following below:


Penile length (in centimeters)

(Mean Value ± Standard Deviation)

Table 1:  Feldmann και Smith Table 



0-5 months


6-12 months


1-2 years


2-3 years


3-4 years


4-5 years


5-6 years


6-7 years


7-8 years


8-9 years


9-10 years 


10-11 years




It is common for adolescent boys to worry about the lentgh of their penis and visit the doctor for evaluation. 

In the vast majority, they have a normal-sized penis, but obesity that very often co-exists, gives the false impression of a small penis as this is 'hidden' in pubic fat (pubis = hairy triangle above penis). 

What are the causes of Micropenis?

There are cases of idiopathic micropenis (=of unknown origin). However, there are also two severe hormonal disorders that may be involved in its etiology. These are:

  • Hypogonadotropic Hypogonadism: insufficient secretion of Gonadotropin-releasing Hormone (GnRH) from the hypothalamus
  • Hypergonadotrophic Hypogonadism: deficient testosterone production due to testicular impairment 

How is Micropenis diagnosed?

The physician performs a thorough clinical examination to measure properly and with accuracy the penile length. At the same time, penile morphology is carefully evaluated in order to exclude any other congenital abnormalities that might potentially give the impression of a small-sized penis (e.g. penile curvature). Then follows the testicular evaluation. If the clinical examination raises the suspicion of micropenis, then special blood tests have to be conducted, in order to diagnose potential hormonal disorders. In boys with concomitant cryptorchidism, special treatment has to be followed.

What is the treatment of Micropenis?

If some hormonal disorder is diagnosed, the boy has to be treated by a specialized Paedoendocrinologist. Specific hormones will be administered, in an effort to stimulate  penile growth.

Given that hormonal therapy is not usually effective in increasing penile size, there were several surgical techniques that were introduced  and performed in the past. However, results were disappointing and many complications arose; as a result, these surgical methods have not been widely adopted in clinical practice.

In general, there are no evidence-based surgical procedures that are recommended today for the treatment of micropenis.