A long-acting (weekly) growth hormone for children
Lonapegsomatropin
A long-acting growth hormone given as a weekly injection to treat growth hormone deficiency in children.
What is Lonapegsomatropin?
Lonapegsomatropin is a long-acting form of growth hormone used to treat growth hormone deficiency in children, helping them to grow and develop normally. Its main advantage is that it is given as an injection under the skin only once a week, rather than daily like older growth hormone treatments. The most common effects are reactions where the injection is given, fluid retention and headache. It can raise blood sugar and affect the thyroid, so these are monitored, and growth is reviewed regularly. It must not be used in children with active cancer. It is prescribed and supervised by a specialist team.
Education and reference only. This is a plain-language guide to Lonapegsomatropin — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Lonapegsomatropin is a long-acting version of growth hormone, the natural hormone that helps children grow. It is used in children who do not make enough growth hormone of their own, a condition called growth hormone deficiency, which can slow their growth. Unlike older growth hormone treatments that are injected every day, lonapegsomatropin is designed to be given just once a week, which can make treatment easier to keep up. It is given as an injection under the skin and is prescribed and supervised by a specialist children's hormone (endocrine) team.
How it works
Growth hormone tells the body to grow, including helping bones get longer and muscles develop, and it has effects on how the body handles sugar and fat. In children who lack enough of it, growth slows down. Lonapegsomatropin supplies growth hormone in a long-acting form that is released slowly after each injection, so a single weekly dose keeps levels topped up across the week. By replacing the missing hormone, it allows the child to grow more normally. Because it acts like the body's own growth hormone, it can also affect blood sugar and the thyroid, which is why these are watched.
Company & origin
Originated / developed by: Specialist manufacturer.
A specialist long-acting growth hormone used in the UK to treat growth hormone deficiency in children, given as a weekly injection.
Practical use
How to take Lonapegsomatropin
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Give the injection under the skin once a week, on the same day each week, as your specialist team has trained you.
- Rotate the injection site each time to reduce redness, lumps or other skin reactions.
- Attend regular appointments so growth can be measured and the dose adjusted as the child grows.
- Report any persistent headaches, vision changes, limp or hip or knee pain, as these need checking.
- Tell the team about any history of cancer, as growth hormone must not be used with active cancer.
Weighing it up
Advantages & disadvantages of Lonapegsomatropin
Advantages
- Given once a week rather than daily, which can make treatment easier to keep up.
- Effectively replaces missing growth hormone to help children grow.
- Given as an injection under the skin that families can be trained to do at home.
Disadvantages
- Commonly causes injection-site reactions, fluid retention and headache.
- Can raise blood sugar and unmask thyroid problems, so monitoring is needed.
- Must not be used in children with active cancer and needs ongoing specialist review.
Practical use
Good to know
The main advantage of lonapegsomatropin is convenience: it is given once a week rather than daily, which can make long-term treatment easier for children and families. It is injected under the skin, and the injection site should be rotated to reduce reactions such as redness or lumps, which are common. It can cause fluid retention, leading to puffiness or aches, and headaches, particularly when treatment first starts. Two things the team will keep an eye on are blood sugar, because growth hormone can raise it, and the thyroid, because growth hormone can unmask an underactive thyroid. A very important safety rule is that it must not be used in children who have active cancer. Treatment is reviewed regularly, including measuring how well the child is growing, to make sure it is working and the dose is right.
Who should not take it / use with caution
- Children with active cancer must not use it.
- It is not used after the growth plates in the bones have closed (the end of growth).
- It is used with care in children who are seriously unwell, and in those with diabetes or thyroid problems, under specialist guidance.
Monitoring
- Regular measurement of the child's growth to check the treatment is working and the dose is right.
- Checking blood sugar and thyroid function over time.
- Watching for headaches, vision changes or hip and knee problems.
Side effects
- Redness, lumps, pain or other reactions where the injection is given.
- Fluid retention causing puffiness or aches, and headaches, especially early on.
- Less commonly, raised blood sugar, an underactive thyroid, or hip or knee problems that cause limping.
Key interactions
- Steroid medicines can reduce how well growth hormone works, so doses may need reviewing.
- It can affect how the body handles sugar, so diabetes treatment may need adjusting.
- Tell the team about all medicines, including any hormone or steroid treatments.
Available as: A solution for injection under the skin, given once a week.
Answers
Lonapegsomatropin: frequently asked questions
What is lonapegsomatropin used for?
It is a long-acting growth hormone used to treat growth hormone deficiency in children, helping them to grow and develop more normally.
How often is it given?
It is given as an injection under the skin once a week, rather than every day like older growth hormone treatments, which can make it easier to keep up.
What are the most common side effects?
The most common are reactions where the injection is given, fluid retention causing puffiness or aches, and headaches, especially when treatment first starts.
Why are blood sugar and thyroid checked?
Growth hormone can raise blood sugar and can unmask an underactive thyroid, so the team monitors these and adjusts treatment if needed.
Can any child take it?
No. It must not be used in children with active cancer, and it is not used once growth has finished; a specialist team decides if it is suitable.
The wider class
About Long-acting growth hormone
Lonapegsomatropin belongs to the long-acting growth hormone class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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