Noonan syndrome

Noonan syndrome (NS) is a genetic disorder affecting girls and boys equally. Several genes* are involved in the disorder. A change in a specific gene causes the problems in growth and development associated with NS.

Short height is one of the main features of NS in childhood, and affects up to 83% of children diagnosed. Puberty can be delayed by up to 2 years, and the usual growth spurt at puberty is either smaller or doesn’t happen at all. Without treatment during childhood, the average adult height for someone with NS is 163cm (5ft 4in) for boys and 152cm (5ft) for girls.

How is NS diagnosed?

Today there are several genetic tests which can confirm the clinical diagnosis of NS in the majority of patients. Before carrying out these tests, doctors look at a range of symptoms and physical features associated with NS to help them identify the condition. Common signs of NS are short height, webbed neck, heart defects, cryptorchidism in boys (failure of the male sex glands or testes to descend into the scrotum), and facial features such as drooping eyelids and low-set, rotated ears. In many cases NS is identified by the presence of a problem called a heart murmur.

The importance of early diagnosis

For a child with NS, the earlier the diagnosis, the better the prospects for treatment. Children who are shorter than normal are often seen by a paediatric endocrinologist, who is a doctor specialising in treating children with growth problems.

Helping children with NS to grow

Some children with NS may be given daily growth hormone injections, which can help them catch up with the growth of other children of the same age during early childhood. Continuing the injections helps maintain normal growth later in childhood, with the final aim of achieving an adult height within the average range. The response to growth hormone treatment varies from one individual to another, but most children who receive treatment over several years will reach a normal or near normal adult height.

In fact, studies have found that when growth hormone treatment is started early, children with NS will grow to an adult height within the normal range for their population and have a normal body composition. This means improved muscle strength and decrease body fat.

Growth hormone injections are normally given once-daily, in the evening. When the child is very young, parents are trained to give these injections. Later on, children can inject themselves when they feel confident enough. Devices are now available that make injecting growth hormone much simpler, more comfortable and less painful. This has been achieved through advances in design such as automated needle insertion and the use of very fine needles. There is a wide choice of devices available, and whilst some require mixing before use and refrigeration once opened, others do not.

To help the doctor select an injection device that matches your requirements, it may help to read the page discussing the features of the various devices.

Meeting the challenge of growth problems

If a child doesn’t grow as fast as other children, this can have an impact on the whole family. Many children who are shorter than their schoolmates may experience emotional problems, bullying and difficulties with daily activities such as sports. For these reasons, it’s important to explain to a child how growth hormone treatment can help to boost their height, and how important it is to continue with the daily treatment.

Meeting the challenge of other problems related to NS

Heart problems are present in around 80% of children with NS. Many of these heart problems are minor and need only annual follow up by a doctor. However, some heart defects will need surgery at some stage. Children with NS may also experience other problems, including:

  • Poor eyesight
  • Unusual bone development
  • Learning disabilities
  • Low weight in infancy
  • Difficulties with feeding
  • Hearing problems

In order to meet the challenges faced in treating the different problems associated with this condition, many different physicians contribute to the treatment of patients with NS: cardiologists, paediatric endocrinologists, genetic


* Gene: The basic unit of heredity, made up of strands of DNA that determine the doctors and others. features that are inherited from parents (for example, colour of eyes and hair).



APROM ID# 1503. December 2009.