Introduction
Hormones are chemicals that circulate within our blood stream to reach targeted organ/tissues, to carry out specific changes/effects. Hormones are secreted by specific organs called ‘endocrine glands’.
Growth hormone (GH), Is a type of hormone secreted by the anterior pituitary gland, responsible for growth spurs in children and adoloscents. It also helps to regulate body composition, body fluids, muscles and bone growth, sugar and fat metabolism. Human Growth Hormone (hGH) can be made synthetically for therapeutic uses and are available as treatment modalities especially for cases of growth hormone deficiency.
What is Growth Hormone deficiency?
Growth hormone deficiency (GHD), can be divided in primary (congenital/since birth) and secondary (acquired). Primary GHD will result in short stature or dwarfism, since GH is required for growth especially during puberty. GHD for those in adulthood experience a decrease in lean body mass, bone mineral density (BMD), and quality of life; an increase in fat mass; and increased rate of fractures, cardiovascular disease, and mortality. This is based on the function of GH, as GH :-
· stimulates protein synthesis
· increases fat breakdown to provide the energy necessary for tissue growth
· antagonizes (opposes) the action of insulin
· contributes to proper bone density
· contributes to heart muscle function
That being said, an excess of growth hormone will also have it’s physiological effects on the human body. After puberty and growth spurs, our body still requires GH to maintain body structure and metabolism. In general, acquired GH deficiency is more rare compared to congenital GH deficiency.
What causes growth hormone deficiency?
GHD that is acquired (not congenital) may be caused by a tumour in the brain. Such tumours that can lead to GHD are for example, a tumour in the pituitary gland or in the hypothalamus.
On top of that, head trauma, irradiation, or even infections may also lead to a reduced production of GH, causing GHD.
What are the symptoms of growth hormone deficiency?
Children with GHD are generally smaller in size/short stature because of the lack of GH to stimulate growth. Central obesity (fat around abdomen), may also be observed.
If GHD develops later in a child’s life, delayed puberty may be observed. In most cases, sexual characteristics and development will be affected. During this period of time, most adolescent may experience low self-esteem as a result of the mentioned short stature or delayed maturation of sexual characteristics (eg. delayed breast developments, delayed deepening of male voice).
In the long run, there would also be reduced bone strength leading to frequent fractures. People with GHD frequently feel tired and lack of stamina. This may be accompanied by an insensitivity to surrounding hot or cold temperatures.
The accompanying psychological effects from low GH are as such:-
· Depression
· Difficulty concentrating
· Poor memory
· Anxiety/ emotional distress
Individual adults with GHD typically have high levels of fat/cholesterol in the blood. This is due to the fact that GH has a role in maintaining fat/cholesterol balance in the body. Adults with GHD are at greater predisposition for diabetes and cardiovascular diseases.
How is growth hormone deficiency diagnosed?
Investigations are usually ordered by paediatricians if a child is not meeting their height and weight milestones. These milestones are an indication of growth and hence, failure to thrive is an indication of possibly underlying disease.
There are multiple tests that can be done to assess GHD. This will be decided by the doctor. Example of blood tests that reflect amount of GH in the body is for example the blood test ‘Insulin-like Growth Factor-1 (IGF-1)’. GH stimulates the production of a protein IGF-1 in the human body, and therefore IGF-1 serves as a protein marker for GH.
Another possible test that can be conducted is called ‘GH stimulation test’. This test involves injection of a medicine or chemical into the veins to stimulate the production of GH in the body. Blood samples will be taken at timed intervals over 2 hours to measure GH levels. The samples will be taken and measured in the lab to be compared with the expected levels of GH at each point of time after taking the stimulant.
Can growth hormone deficiency be treated?
Yes it can! Treatment of GHD typically involves carefully titrated levels of GH. GH injection can be self-administered or by the child’s parents.
GHD treatment needs to be carefully monitored with follow ups to decide the optimum amount of GH injection needed for it’s effectiveness.