Growth Hormone Deficiency
Growth Hormone Deficiency
Growth hormone (GH) is a hormone produced by the pituitary gland, a small gland located at the base of the brain. It plays an important role in growth during childhood and continues to have important functions throughout adult life.
Growth hormone helps regulate body composition, muscle and bone health, metabolism and the way the body uses fats and carbohydrates. It also contributes to physical strength, energy levels and overall quality of life.
Growth hormone works partly by stimulating the production of insulin-like growth factor 1 (IGF-1), which is produced mainly by the liver and has effects on many tissues throughout the body.
When the pituitary gland does not produce enough growth hormone, this is known as growth hormone deficiency (GHD).
What causes Growth Hormone Deficiency?
Growth hormone deficiency can be present from birth (congenital) or develop later in childhood or adulthood (acquired).
In some people, no specific cause can be identified. This may be described as idiopathic growth hormone deficiency.
Possible causes include:
- Abnormal development of the pituitary gland or hypothalamus before birth
- Genetic conditions affecting pituitary development or growth hormone production
- Pituitary or hypothalamic tumours
- Surgery involving the pituitary gland or surrounding structures
- Radiotherapy to the brain or pituitary region
- Head injury or other significant brain injury
- Conditions affecting the blood supply to the pituitary gland
- Inflammation or other disorders affecting the pituitary or hypothalamus
Growth hormone deficiency can occur on its own or alongside deficiencies of other pituitary hormones. (Endocrine)
Growth Hormone Deficiency in Adults
Adult growth hormone deficiency is most commonly associated with damage or disease affecting the pituitary gland or hypothalamus.
People who have had a pituitary tumour, brain tumour, pituitary surgery or radiotherapy to the brain may be at increased risk. GHD may also occur as part of broader hypopituitarism, where the pituitary gland does not produce one or more of its other hormones adequately.
Growth hormone deficiency may affect several aspects of health. However, symptoms vary considerably between individuals and many of the symptoms can also occur with other medical conditions or with other pituitary hormone deficiencies.
A diagnosis therefore requires assessment by an experienced endocrinology team rather than relying on symptoms alone.
Symptoms of Growth Hormone Deficiency
Adults with growth hormone deficiency may experience some of the following symptoms or changes:
- Increased body fat, particularly around the waist
- Reduced muscle mass
- Reduced muscle strength
- Reduced stamina and exercise capacity
- Persistent tiredness or reduced energy
- Changes in blood cholesterol, including increased LDL cholesterol
- Reduced bone mineral density and an increased risk of fractures
- Changes in body composition
- Reduced sense of physical wellbeing
- Reduced quality of life
- Low mood, anxiety or psychological difficulties
- Increased sensitivity to cold or heat
- Difficulty maintaining physical fitness
Not everyone with GHD will experience all of these symptoms.
Some people may have relatively few symptoms despite having significant biochemical growth hormone deficiency, while others may experience substantial effects on their quality of life. (Endocrine)
How is Growth Hormone Deficiency diagnosed?
Diagnosing adult growth hormone deficiency can be complex.
A diagnosis is usually based on a combination of:
- Medical history
- Symptoms and clinical assessment
- Assessment of other pituitary hormone deficiencies
- Blood tests, including IGF-1
- Growth hormone stimulation testing
An IGF-1 blood test can provide useful information, but an IGF-1 result alone does not usually confirm or exclude adult growth hormone deficiency. IGF-1 levels can be influenced by several other factors and conditions.
Because growth hormone is released by the pituitary in pulses, a single random GH blood test is generally not suitable for diagnosing adult GHD. Stimulation testing is usually required. (Endocrine)
Growth Hormone Stimulation Tests
A stimulation test measures how well the pituitary gland can respond when the body is stimulated to release growth hormone.
Insulin Tolerance Test (ITT)
The insulin tolerance test has traditionally been considered an important reference test for diagnosing adult GHD.
Insulin is administered under carefully controlled medical supervision to temporarily lower blood glucose. Blood samples are taken at specific intervals to measure the body's growth hormone response.
Because the test deliberately causes hypoglycaemia, it is not suitable for everyone and requires appropriate medical supervision.
Glucagon Stimulation Test
A glucagon stimulation test may be used when an insulin tolerance test is unsuitable or contraindicated.
Glucagon is administered and blood samples are collected over a number of hours to assess the growth hormone response.
The exact testing protocol and interpretation of results can vary between specialist centres.
Macimorelin Stimulation Test
Macimorelin is an oral medicine that stimulates the release of growth hormone and can be used as a diagnostic test for adult GHD.
The medicine is taken as an oral solution, followed by blood samples at approximately 45, 60 and 90 minutes to measure the growth hormone response.
Macimorelin, marketed in the European Union as Ghryvelin, is authorised by the European Medicines Agency for the diagnosis of growth hormone deficiency in adults. Its availability and use may depend on local specialist endocrine services. (European Medicines Agency (EMA))
Your endocrinologist will decide which stimulation test is most appropriate based on your medical history, other hormone deficiencies and any conditions that could make a particular test unsuitable.
Treatment of Growth Hormone Deficiency
Growth hormone replacement may be considered for adults with confirmed growth hormone deficiency when treatment is appropriate for the individual.
Treatment decisions are made by an endocrinologist and take into account:
- The severity and cause of GHD
- Other pituitary hormone deficiencies
- Your symptoms and quality of life
- Bone health and body composition
- Other medical conditions
- Previous or current pituitary or brain tumours
- Potential benefits and risks of treatment
- Your response to treatment
Other pituitary hormone deficiencies should generally be appropriately assessed and treated as part of the overall management of hypopituitarism.
Growth hormone replacement is not suitable for everyone with a low IGF-1 level or suspected GHD, and treatment should only be started following appropriate specialist assessment. (Endocrine)
Growth Hormone Replacement
Growth hormone replacement uses recombinant human growth hormone (somatropin).
Treatment is normally administered as an injection under the skin using an injection pen.
Patients are generally taught how to administer their own injections at home. The dose is individualized and usually started at a low dose before being adjusted according to factors such as age, symptoms, side effects and IGF-1 levels.
There are also newer long-acting growth hormone preparations in some countries, although availability and prescribing arrangements vary.
In Ireland, somatropin and biosimilar products are available under specialist prescribing and monitoring arrangements. (HSE.ie)
Monitoring Treatment
Regular follow-up is important when receiving growth hormone replacement.
Your endocrinology team may monitor:
- IGF-1 levels
- Symptoms and quality of life
- Growth hormone dose
- Other pituitary hormone replacement
- Body composition and metabolic health
- Bone health where appropriate
- Possible side effects
The dose may be adjusted according to your individual response.
The aim is to achieve an appropriate IGF-1 level while avoiding excessive replacement and minimizing side effects. Current endocrine guidance recommends individualized dosing and maintaining IGF-1 within the appropriate age-related range. (Endocrine)
Possible Side Effects
Growth hormone replacement is generally well tolerated when appropriately prescribed and monitored.
Some people may experience:
- Swelling or fluid retention, particularly in the hands or feet
- Joint or muscle aches
- Headaches
- Numbness or tingling
- Carpal tunnel symptoms
These effects are often related to the dose and may improve following dose adjustment.
Your endocrinology team should be contacted if you develop new or troublesome symptoms while taking growth hormone.
Growth Hormone and Pituitary Tumours
Growth hormone treatment requires particular consideration in people with a history of pituitary or other brain tumours.
Treatment decisions should take account of the individual's tumour history, treatment and current clinical and imaging findings.
Growth hormone replacement is generally not started when there is active or suspected tumour growth. Your endocrinologist will determine whether treatment is appropriate and whether additional monitoring or imaging is required.
How long will I need Growth Hormone Treatment?
The duration of treatment varies from person to person.
Unlike the approach described in some older guidance, treatment should not automatically be viewed as a fixed 6–9 month course for every adult.
In some healthcare systems, a period of treatment is used to assess whether an individual experiences meaningful benefits, particularly in quality of life. Treatment may then be continued when there is evidence of benefit and it remains clinically appropriate.
NICE guidance in the UK, for example, recommends reassessing quality of life after approximately nine months. However, NICE guidance is UK-specific and should not be interpreted as an Irish prescribing or reimbursement rule. (Nice)
For people receiving growth hormone replacement in Ireland, treatment decisions should be made with their endocrinology team in accordance with current clinical evidence, the individual's circumstances and applicable Irish prescribing and reimbursement arrangements.
Growth Hormone Deficiency in Children and Young People
Growth hormone has an especially important role during childhood and adolescence because it contributes to normal growth and development.
Children with GHD may have:
- Slower growth
- Short stature compared with expected growth patterns
- Delayed bone maturation
- Reduced muscle mass
- Increased body fat
- Low blood glucose in some infants with severe GHD
Children with GHD may also have deficiencies of other pituitary hormones.
Growth hormone treatment in children is managed differently from adult replacement therapy. Children should be assessed and monitored by a specialist paediatric endocrinology team.
The HSE recognises growth hormone deficiency as a condition managed within specialised paediatric endocrinology services in Ireland. (HSE.ie)
Living with Growth Hormone Deficiency
Growth hormone deficiency can form part of a wider pituitary disorder, and managing it may involve several hormone replacement therapies.
If you have a pituitary condition, it is important to attend regular endocrine follow-up and discuss any persistent symptoms with your healthcare team.
Symptoms such as tiredness, changes in body composition, low mood or reduced exercise capacity can have many possible causes, including other pituitary hormone deficiencies. They should therefore be assessed in the context of your overall health rather than automatically attributed to GHD.
Do not start, stop or change growth hormone treatment without discussing it with your endocrinologist or specialist healthcare team.
Key Points
- Growth hormone is produced by the pituitary gland and has important effects throughout life.
- Growth hormone deficiency can be present from birth or develop later.
- Pituitary tumours, surgery, radiotherapy and brain injury are among the possible causes of acquired GHD.
- Adult GHD can affect body composition, muscle strength, bone health, metabolism, energy and quality of life.
- A diagnosis generally requires specialist assessment and, where appropriate, a growth hormone stimulation test.
- IGF-1 is useful in assessment and monitoring but does not usually diagnose adult GHD on its own.
- Treatment involves individualized growth hormone replacement for people with confirmed deficiency who are considered suitable for therapy.
- Regular monitoring, including IGF-1 testing, is important during treatment.
- Treatment decisions should always be made with an endocrinologist experienced in managing pituitary disorders.
Important Information
The information on this page is intended for general educational and support purposes and is not a substitute for professional medical advice, diagnosis or treatment.
If you are concerned that you may have growth hormone deficiency, speak with your GP or endocrinology team. If you have already been diagnosed with a pituitary condition, discuss any new or persistent symptoms with your endocrinologist.
Treatment and prescribing arrangements can change, and individual eligibility for growth hormone replacement should be determined by your specialist healthcare team.
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