It might surprise you to find out that growth hormones are still needed by adults even after we stop growing. So, why do we still need this hormone produced by the pituitary gland if we’re not growing any more?
With ageing, lean body mass decreases and adipose tissue increases. This may be due to age-related decreases in growth hormone and insulin-like growth factor 1 (IGF-1).
IGF-1, also known as somatomedin C, is produced by the liver and other tissues in response to growth hormone stimulation. The decrease in the activity of the growth hormone–IGF-1 axis is termed somatopause or hyposomatotropism of ageing.
It is associated with a decline in physical function, muscle strength and vitality. Additionally, frailty, central adiposity (deposition of fat around the abdominal area), accelerated risks for cardiovascular (heart) complications, and deterioration of mental function, can occur.
Therefore, adequate growth hormones are important to help maintain muscle mass and control fat accumulation, as well as to prevent the consequences mentioned above. These hormones also play a role in regulating cholesterol levels, bone density, and the density of our high-density lipoproteins (HDLs). They also contribute to normal brain function.
Cause and symptoms
Growth hormone is produced by somatotroph cells within the anterior pituitary gland. The production of these hormones is triggered by growth hormone-releasing hormone (GHRH) and inhibited by somatostatin, which is produced by the hypothalamus.
Usually, a deficiency of growth hormone is caused by damage to either the pituitary gland or the hypothalamus. This damage can be from a tumour, surgery or radiation to treat the tumour, or problems with blood supply to the pituitary gland.
Children and adults can both suffer from a lack of growth hormone. In general, an adult who has too little growth hormone will have reduced physical performance, psychological well-being and quality of life.
Specific symptoms include:
- Less strength, stamina and ability to exercise without taking a rest.
- Reduced bone density and a tendency to have more bone fractures as they get older.
- Greater sensitivity to heat and cold.
- Less muscle (lean body mass).
- Changes in the make-up of their blood cholesterol.
- Decreased sexual function and interest.
- A higher level of body fat (both subcutaneous and visceral), especially around the waist.
- Anxiety and depression.
A doctor or an endocrinologist will usually test for adult growth hormone deficiency in patients who have had surgery around the pituitary gland and hypothalamus area, sustained injuries, or a history of pituitary disorders.
In cases where the pituitary gland is known to have a disorder or problem, a magnetic resonance imaging (MRI) scan will probably be ordered before any treatment is performed.
By doing so, the doctor can more accurately monitor how the treatment is affecting the problem (e.g. a tumour). As growth hormones are released in pulses, randomly sampling the blood to measure growth hormone levels is not a reliable indicator of its actual level.
In addition, unlike children, adults absorb growth hormone from the blood quickly; therefore, a blood test conducted on a healthy individual will tend to show low levels of growth hormone. Instead, endocrinologists check the pituitary gland’s response when it is stimulated to produce growth hormone.
The insulin tolerance test (ITT), arginine test and GHRH test are some examples of commonly-used stimulation tests. These tests take about two to three hours, and you will be asked not to eat before the test.
When the doctor confirms that adult growth hormone levels are low, daily doses of recombinant human growth hormone will be prescribed. These hormones are administered once a day via injection under the skin.
The injection can be done by either the patient or a family member/caregiver at home after some quick training. Every four to eight weeks, the patient should see the doctor for monitoring and a blood test to help the doctor decide if more or less hormone is needed.
A person suffering from too much growth hormone may suffer from muscle and joint pain, swelling (fluid retention), and pain or numbness in the hands caused by carpal tunnel syndrome. The doctor will lower the dosage of growth hormone if such symptoms occur.
If the cause of the problem is a tumour, the patient will need to undergo an MRI every year in order for the doctor to monitor the status of the tumour. It is currently unknown if growth hormone therapy causes tumours in the pituitary gland to grow.
Finally, the patient’s blood cholesterol and bone density will also be monitored. With treatment of adult growth hormone deficiency, both of these measures should show signs of improvement.
Growth hormone therapy has also been proven to improve lean body mass, exercise tolerance, personal productivity, and quality of life. People with active cancer or tumours should not be given growth hormone therapy.
Similarly, those who are seriously ill as a result of complications from open heart or abdominal surgery, who have multiple injuries from a major accident, or who have breathing problems, are advised against growth hormone therapy.
The use of growth hormone can affect the body’s ability to use insulin, so patients with diabetes should be vigilant about monitoring blood sugar levels if they decide to take growth hormone therapy.
By Datuk Dr Nor Ashikin Mokhtar
Published in Star Newspaper, 11 Jul 2022