What is growth hormone (GH)?
Growth hormone (GH) is a natural protein hormone, which is secreted by the pituitary gland. GH therapy is a synthetic form of human growth hormone with the same chemical structure as naturally made GH. It is made using recombinant DNA technology, meaning it is made in a lab. GH is not a steroid.
Why does my child need GH?
GH is indicated as a treatment in children with GH deficiency.
GH may also be used to help growth in other conditions:
- Children with chronic diseases/syndromes that impact growth.
- Children with short stature of unknown cause (idiopathic short stature)
- Children who were born small for gestational age who continue to have short stature.
How is GH deficiency diagnosed?
GH deficiency is diagnosed through growth hormone stimulation testing and assessment of growth rate. To learn more about GH deficiency, please see the article Growth hormone (GH) deficiency.
Which GH products are available in Canada?
There are various brands of GH available in Canada. There are some differences in cost of the medication between companies. Health Canada has approved all of these GH products for use in children. In Ontario we are permitted to use (in alphabetical order):
- Genotropin
- Ngenla
- Norditropin
- Omnitrope
- Saizen
The patient and family are offered all the products available, and they chose the product they prefer.
How is the best GH dose for each child determined?
Various dosage ranges depend on the following.
- Diagnosis.
- Literature recommendations (generally: 0.03 mg/kg/dose -0.05 mg/kg/dose).
- Goals of and response to treatment.
- Blood tests, including insulin-like growth factor-1 (IGF-1) level. IGF-1 production is stimulated by growth hormone to promote growth.
- Body weight.
How is GH given?
GH must be given by subcutaneous (under the skin) injection. As GH is a protein, it can be digested in the stomach before the body is able to absorb it, so it will not work if taken by mouth.
Where are the subcutaneous injections given?
GH is given into the arms, legs, buttocks or abdomen. Injections are rotated between these sites. Parents and caregivers are taught how to administer the injections at home.
How often are injections given?
Injections of most types of GH are given once per day, six times per week. Missed injections may be given on the seventh day. There is also one type of long-acting GH (Ngenla) which is given once a week. Ngenla is only indicated for GH deficiency.
GH therapy requires long-term commitment by children and their families.
When are GH injections given?
GH injections can be given at any time of day. However, it is generally recommended that injections be given in the evening before bed, to match the natural production of GH since children normally make more GH at night.
For strategies on how to give injections to your infant, child or teenager, please see the Comfort Promise and CARD learning hubs.
How much growth can we expect?
In general, before GH therapy begins, a child’s growth is less than five centimetres (cm) per year. During the first year of GH therapy, growth may reach up to eight to 10 cm. Usual growth is expected (approximately five cm+ per year) following the first year of treatment.
How often will we need to be seen in clinic for follow up?
Your child will need to be seen in clinic every four to six months during the initial year of GH therapy. During puberty, adolescents may be seen every four months.
What can I expect at these clinic visits?
- assessment of height and weight
- review of health and side effects
- physical assessment (general)
- bone age X-rays of the left wrist and hand (periodically)
- blood testing (approximately once per year)
- new dose and prescription of GH based on new weight and response to treatment
How long will my child be on GH?
GH therapy will continue until one or more of the following occur:
- Until full growth has been largely attained (as measured by very little recent growth) and a bone age X-ray shows near closure of growth plates and a bone age of 14-16 years.
- You and your child no longer wish to continue with therapy.
- Sometimes, children do not respond to GH therapy so the health-care team may consider stopping the therapy for this reason.
- Some young adults may require continuation of GH therapy into adulthood. Repeat testing for adult GH deficiency may be required to determine if GH deficiency persists into adulthood.
What effect does GH therapy have on a child?
Children on GH therapy may experience the following:
- increased height
- increased weight
- increased muscle mass
- increased bone mass
- increased strength
You may also notice:
- reduction of adipose (fat) tissue
- increased metabolism
- increased appetite
What are the side effects of GH therapy?
GH is one of the most studied medications/hormones. To date, thousands of research studies and articles have been published on the use of GH. It has a very safe drug profile. Synthetic GH has been used in Canada since 1986. There are no known drug interactions and routine immunizations may be given. Side effects of GH therapy are very rare. However, there are some potential risks which will be monitored for at your child’s follow-up visits.
Headache: Idiopathic intracranial hypertension (IIH)
IIH can occur in 1 in 1000 children receiving GH. It is not clear why it occurs. One possible cause is that retention of salt and water that can occur at the beginning of GH treatment may cause increased pressure within the fluid that circulates around the brain. Children will complain of or experience headache, nausea or vomiting. It may occur within the first months of GH treatment and will resolve rapidly when GH is stopped and restarted at a lower dose and increased slowly over time (usually without further problems).
Typically, the child will wake up with a headache one to two days in a row (with or without nausea and vomiting) that will not improve with administration of acetaminophen or ibuprofen.
Slipped capital femoral epiphysis (SCFE)
SCFE occurs when the growing part of bone (epiphysis) at the top of the thigh bone (femur) slips out of alignment. This may occur in children who are growing quickly, are overweight or who have GH deficiency after treatment for leukemia or brain tumours. Symptoms of SCFE are hip and/or knee pain or limping.
SCFE is not caused directly by GH treatment but is related to the rapid growth spurt that can occur after treatment starts.
Scoliosis
Scoliosis is an abnormal curve of the spine. In children with scoliosis, the degree of curvature may worsen when growth accelerates with the use of GH. Your child’s spine will be assessed regularly.
Risk of cancer
GH stimulates the growth of cells however studies have not shown an increased rate of cancers in children treated with GH. During GH treatment, IGF-1 levels are monitored, and the health-care team will make adjustments to keep this in the normal range. Some studies have associated very high levels of IGF-1 with tumour formation, although it is unclear whether this is the cause, or purely coincidence. The use of GH in cancer survivors is not associated with increased risk of recurrence of the initial cancer, or of death.
Risk of diabetes
One of the natural functions of GH is to increase the amount of sugar in the blood in times of stress. It does this by decreasing the body’s sensitivity to insulin (a hormone that helps transport sugar from blood into cells in the body). Reduced sensitivity to insulin may lead to the development of type 2 diabetes. Most studies do not show an increased incidence of type 1 or 2 diabetes associated with GH treatment. However, factors that may increase the risk include children taking high dose glucocorticoids and those that are overweight or have a parent with diabetes. Symptoms of diabetes include increased thirst and urination.
Risk of stroke
One study showed an increased risk of stroke among adults who were treated with GH as children. However, the absolute risk (the number of people who developed stroke) was very small. Major professional organizations continue to feel that, for properly selected patients, GH remains a safe and effective treatment.
Other potential side effects
- Swelling of hands and feet (more frequent in adults).
- Increase in number of moles or nevi (more common in Turner syndrome).
- Lipoatrophy: loss of fat under the skin surface causing a dip or dimple from repeated injections to the same site.
- Lipohypertrophy: soft grape like lump at the injection site which represents a build-up of fat or scar tissue from repeated injections to the same site.
Is there any additional information we need to know about GH therapy?
- Use a small cooler with ice/cold gel pack for travel.
- A new needle/syringe is needed for every injection. Proper disposal in a sharps container is required.
- No need for a medical alert bracelet (unless necessary for other medical conditions or medications).
- Treatment may be continued during illness.
Where do I obtain GH medication?
If a patient has GH deficiency they must pick up their prescription at the SickKids Shoppers Drug Mart or another pharmacy that is designated, such as the pharmacy at McMaster. They can only pick up their GH medication at a local pharmacy if they do not have GH deficiency (e.g., idiopathic short stature, Turnes syndrome, small for gestational age).
How do we get started?
You and your child will review the information and decide which GH product will best suit your lifestyle. Once you have decided, you will reach out to our team to provide your decision. An enrollment form will then be sent to the GH company along with a prescription to the appropriate pharmacy. The GH company will then reach out to you to schedule a teaching session with their field nurse. You can expect to be seen for a follow up appointment in the Endocrinology Clinic about four months after starting therapy.