Micropenis in children, what it means and when parents should be concerned

Sinar Daily

20-05-2025

At birth, some health conditions in infants aren't immediately obvious. One such condition is micropenis—a medical term describing a penis that is significantly smaller than the average size for a newborn, despite appearing normal in shape and structure.
According to Sunway Medical Centre consultant paediatrician and paediatric endocrinologist Dr Ch'ng Tong Wooi, the condition may not be immediately noticeable. The penis may look structurally normal in the early stages, but as the child grows, it may not grow adequately—sometimes affecting reproductive health and sexual function later in life.
Doctors diagnose micropenis using a specific measurement known as Stretched Penile Length (SPL). If the SPL falls more than 2.5 standard deviations below the average for the child's age, it may be classified as micropenis. In newborns, this typically means a stretched length of less than 2.5 centimetres, measured from the tip to the base of the penis during a physical exam conducted by an experienced healthcare provider.
As for the underlying causes? Dr Ch'ng says they often stem from hormonal imbalances—particularly issues in the way the body produces or responds to male hormones like testosterone. Early diagnosis is crucial, as prompt treatment during infancy or early childhood can help improve outcomes and support normal development during puberty.
These causes generally fall into several categories such as:
Hypogonadotropic Hypogonadism
This condition occurs when the brain does not send the right signals to the body to produce testosterone. It comes from areas of the brain called the hypothalamus or pituitary gland that are supposed to tell the testicles to make testosterone. Some conditions include Kallman syndrome where the brain's signal is missing, which not only may lead to a micropenis but also compromises a sense of smell by reducing it.
The second example is congenital hypopituitarism which is a condition where the pituitary gland does not make enough hormones. Septo-optic dysplasia is also a condition that may lead to a micropenis, which also affects brain and eye development, sometimes linked to hormone problems.
Primary Hypogonadism
This is a condition that defines a problem in the testicles themselves, according to the doctor, where the brain is already sending the right signals, but the testicles are unable to respond properly and do not make enough testosterone to develop normally.
Conditions such as Klinefelter syndrome, congenital anorchia and testicular damage are included under this category. The first is a genetic condition where boys have an extra X chromosome, the second a condition where testicles are absent or did not develop properly, while the last is caused by certain infections, injuries or treatments.
Testosterone Activation Problems
This is when the body cannot use testosterone properly, where it may be present but the body fails to convert it into the active form or does not respond the way that it should. Examples of specific conditions are 5-alpha reductase deficiency, where the body cannot convert testosterone into a stronger form called DHT, which is a hormone needed for male development, and low growth hormone (GH) which can affect overall development including the penis.
Androgen Insensitivity
Last but not least, the body may also ignore testosterone despite its presence through the cells ignoring it, 'as if they are 'deaf' to the hormone.'
Dr Ch'ng said examples include complete or partial androgen insensitivity syndrome which is a genetic condition defined as the body's tissues not responding well to male hormones.
'Understanding the cause helps doctors decide the best treatment. Some conditions can be treated with hormone therapy early in life to support normal growth, while others may need ongoing care from hormone or genetic specialists,' she said, adding that in some cases, causes are unknown, leading to a label by doctors as 'idiopathic.' Sunway Medical Centre consultant paediatrician and paediatric endocrinologist Dr Ch'ng Tong Wooi.
Warning signs
Parents are urged to do physical examination on babies upon birth, where a micropenis is most of the time noticeable. However, there are paediatricians trained to look for this and other physical signs as part of routine newborn care.
'For some people, it might not be obvious until the child is a little older, especially if the penis does not grow as expected in the early months or during puberty,' Dr Ch'ng said.
Additionally, for some parents, they only become concerned later if they notice that their child's penis seems unusually small for his age or smaller compared to his other siblings.
'If the child is growing normally but the penis doesn't seem to be getting bigger with time, that might raise a concern. Parents might also notice other signs that suggest a possible medical issue, such as undescended testicles (testicles not in the scrotum), unusual genital appearance or delayed puberty,' Dr Ch'ng said.
Further emphasising early diagnosis, she said that it is important to do so at a young age since micropenis most of the time is caused by low testosterone which is more effectively treatable when the child is still small, through small doses of testosterone through injections.
'This is usually done during infancy and can help the penis grow closer to a typical size. In some cases, additional hormone therapy may be needed later,' she said, adding that some people might need surgery, although it is a rare case and only considered in very specific situations.
'Catching the condition early also allows doctors to check for other related health issues and plan for future care for the sake of their children,' she added.
Can micropenis affect fertility or sexual function later in life? Micropenis can sometimes affect fertility and sexual function, but this depends on the cause, said the doctor.
Dr Ch'ng said that the problem affects men differently, where some might only consist of concerns towards size.
'If the problem is only with size and hormone levels are otherwise normal, many boys grow up to have normal sexual function. However, if the condition is linked to hormone imbalances or testicular problems, fertility could be affected.
'With proper treatment and monitoring from an early age, many boys with micropenis can still go through puberty, develop normally, and lead fulfilling adult lives,' she said when contacted by Sinar Daily recently.
Medical and emotional support
Dr Ch'ng said that some parents need ongoing medical support upon diagnosis, which is often provided by a paediatric endocrinologist who can guide testing and treatment, adding that some concerns emerging from other health issues may require a urologist or geneticist.
Emotionally, some parents may face problems processing the information, where the doctor recommended speaking to a child psychologist or a counsellor, considered very helpful, in order for the child to grow healthily along with treatment and managing stress and questions.
She also suggested connecting with others with similar experiences either through friends, support groups or online communities, which could go a long way to help patients grow up with confidence and self-esteem.