Kallmann syndrome

  • Kallmann syndrome is a condition where the body does not make enough of a hormone called gonadotrophin-releasing hormone (GnRH). The role of GnRH is to stimulate the testicles in males and the ovaries in females, to make sex hormones. If not enough of these hormones are made, the child will not enter puberty and will not be able to have children of their own without special treatment. 

    Kallmann syndrome is an inherited condition, meaning it is passed on from parents to their children. Mothers can pass on the gene to their daughters and sons, but fathers can usually only pass it onto their daughters. The condition is five times more common in boys (one boy in every 10,000) than in girls.

    Treatment for Kallmann syndrome is generally effective, and includes hormone replacement. 

    Kallmann syndrome is also known as hypothalamic hypogonadism, familial hypogonadism with anosmia, or hypogonadotropic hypogonadism.

    Signs and symptoms of Kallmann syndrome

    • From birth, children with Kallmann syndrome have either very poor or no sense of smell. This cannot be treated.
    • Boys can have a small penis and experience delayed puberty.
    • Girls have a delay in breast and pubic hair development and no menstruation (monthly period).
    • If not treated, both boys and girls will be infertile (not able to have children).

    Sometimes Kallmann syndrome can also affect the kidneys, ears, heart, eyes and parts of the brain. Some children with Kallmann syndrome will have a cleft palate, obesity, problems with sight or hearing, or an intellectual disability. However, not everyone with Kallmann syndrome has all of these extra problems.

    When to see a doctor

    If your child has not started showing signs of puberty around the same time as their peers and you are concerned, see your GP. This is especially important if your child also has a history of reduced or absent smell or taste. The smell of food is part of how we taste, so not being able to smell properly means some children may find unusual food combinations appetising.

    Your child may be referred to a paediatrician or paediatric endocrinologist (hormone specialist). Kallmann syndrome is usually diagnosed after several tests have been done to work out why the growth spurt that usually comes with puberty is late. It is normal for sex hormones to be low in children, so a test called a stimulation test is done. An injection of GnRH is given and levels of the sex hormones are measured. If they stay low, Kallmann syndrome is diagnosed.

    Treatment for Kallmann syndrome

    Hormone replacement is given to both boys and girls. Boys need a hormone called testosterone which lets them grow and develop during puberty. Girls need the female sex hormones oestrogen and progesterone. If they wish to have children, both boys and girls will also need other hormones so their bodies can make sperm and eggs. 

    Hormone replacement is a long-term treatment. The type of hormone and how it is given will depend on what will work best for your child at different ages. Sometimes the hormones are given as tablets; other times they are given as injections.

    As well as helping with development during puberty, these hormones are essential for your child's body to lay a good foundation for bone strength and to reduce the risk of osteoporosis (weak bones) in later life.

    There is no treatment for the lack of a sense of smell. Not being able to smell properly can also be dangerous, as you cannot smell smoke or know when food has gone off.  


    Your child should have regular appointments with an endocrinologist, and continue these appointments as adults. If other parts of the body are affected (such as the kidneys or the heart), then other medical professionals will also be involved in your child's care.

    Key points to remember

    • Kallmann syndrome is an inherited condition causing the body to not make enough sex hormones. 
    • If left untreated, your child will not enter puberty and will not be able to have children. 
    • Kallmann syndrome also affects the sense of smell. 
    • Long-term treatment with hormone medications is needed for normal growth and development, and to enable your child to have children in the future.

    For more information

    Common questions our doctors are asked

    Is there any cure for Kallmann syndrome? 

    Not yet. Finding a cure for genetic (inherited) disorders is very difficult, and research into life-threatening genetic disorders is prioritised. Treatment is usually very effective for Kallmann syndrome and side-effects are minimal.

    What should we do if my child has no sense of smell?

    Your child will need to be educated on other ways to assess freshness of food and visual signs that food may not be suitable for eating. All smoke detectors should be regularly checked in the home.

    Developed by The Royal Children's Hospital Endocrinology department. We acknowledge the input of RCH consumers and carers.

    Reviewed June 2018.

    This information is awaiting routine review. Please always seek the most recent advice from a registered and practising clinician.

    Kids Health Info is supported by The Royal Children’s Hospital Foundation. To donate, visit www.rchfoundation.org.au.


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