The growth hormone stimulation test is a test that measures the capacity of the pituitary gland and its ability to produce growth within the body. Until several years ago, the accuracy of the test to determine whether or not a person, in fact, has the deficiency has been increasingly questioned because of the variability and increasing acceptance of the deficiency. The role of the growth hormone has previously been determined as the sole function of height. For this exact reason, the growth hormone has been used as a form of replacement therapy in growth hormone deficient children and discontinued in adulthood; however, the growth hormone continues to be produced in significant quantities throughout the adult life. This hormone remains the most abundant hormone in the adult pituitary gland.
The adult growth hormone deficiency is continuously being recognized and has been thought to be associated with premature mortality. The growth hormone deficiency has been associated with neuropsychiatric-cognitive, cardiovascular, neuromuscular, metabolic and skeletal abnormalities. Most of these can be reversed with the growth hormone therapy. The insulin tolerance test remains the gold standard dynamic test to diagnose adult growth hormone deficiency. Pegylated human growth hormone therapy is on the horizon in a convenient once a week dosing.
What Causes Adult Growth Hormone Deficiency?
Adult-onset growth hormone deficiency may present two different and distinct clinical solutions which include: children with growth hormone deficiency transitioning to adulthood or growth hormone deficiency acquired during adulthood- Structural, trauma or idiopathic. There is a two or three-fold increase in standardized mortality in these patients with hypopituitarism. The increased mortality is most likely related to macrovascular disease, and the fact that these patients with increased mortality were replaced with steroids, thyroxine, and a majority were on male hormone replacement which led some experts to believe that the growth hormone deficiency may have contributed to the increased mortality. The growth hormone is the first to deplete following any pituitary insult. It was not until the year 1995 that the concept of the growth hormone replacement became popular and recognized.
The cause of adult growth hormone deficiency is the result of permanent damage of the pituitary gland. This damage may have been caused during childhood or adulthood, and it interferes with the production of the growth hormone. This damage is also most commonly caused by a pituitary tumor. Damage to the pituitary gland may begin from the tumor itself, or it can occur as a result of medical intervention to treat the tumor. Some of these interventions include surgery and radiotherapy. Some children are born with the inability to produce the growth hormone and therefore fall victim to the deficiency throughout their lives.
Signs and Symptoms of Growth Hormone Deficiency
The signs and symptoms of growth hormone deficiency can vary depending on the age of the person that is suffering from the disorder. An adult with the growth hormone deficiency will experience different signs and symptoms of that of a child suffering from the same deficiency. Depending on the age of the person, the signs and symptoms most often vary and have various effects on the person.
Children with growth hormone deficiency typically grow less than two inches per year. Compared to children with normal levels of the growth hormone, children without the deficiency grow approximately two and a half inches per year from age one until they hit puberty; then they can grow up to four inches in a year.
Adults that have growth hormone deficiency can vary and many adults who have this condition can experience a combination of the symptoms that are listed later on. Here are the signs and symptoms of both children and adults that may be encountered in those that have a growth hormone deficiency.
Signs and Symptoms in Children:
- Child’s face may appear younger than children without the growth hormone deficiency that is the same age
- Delayed puberty- sometimes, children with growth hormone deficiency will not hit or experience puberty
- Increased fat around the child’s face and stomach
- Mild to moderate chubbiness
- Slow tooth development
- Sluggish or very slow hair growth
Signs and Symptoms in Adults:
- Anxiety and depression
- Baldness (in men)
- Decreased in sexual function and interest
- Decreased muscle mass and strength
- Difficult to concentrate and lack of memory
- Dry, thin skin
- Elevated triglyceride levels
- Fatigue and/or tiredness
- Heart problem
- High levels of LDL (“bad”) cholesterol
- Insulin resistance
- Lower tolerance to exercise
- Reduced bone density, making you more susceptible to developing osteoporosis
- Sensitivity to heat and cold
- Very low energy levels
- Weight gain especially around the midsection
- Central adiposity
- Fibromyalgia syndrome
- Neuromuscular dysfunction
- Prothrombotic state
- Decreased sweating and thermoregulation
- Social isolation
- Decreased bone density
These are all common symptoms for children and adults that suffer from growth hormone deficiency. Many people can experience more than one sign or symptom and can often be misdiagnosed before the proper tests are performed. It is important that you express all concerns to your doctor or health care provider so that they can effectively diagnose the problem that you are experiencing.
It is important to understand that not everyone with the growth hormone deficiency will have the same symptoms. Some people will only experience one or two symptoms while others have multiple symptoms. Fortunately, there are certain tests that can be performed and exams that can test your pituitary gland and diagnose the growth hormone deficiency accurately.
It is very important that you talk to professional doctors or your child’s doctor right away if you or your child is experiencing any of the previous growth hormone deficiency symptoms that were listed. Even if you are uncertain if the symptoms are linked to the growth hormone deficiency, it is important to express your concerns to your doctor.
Clinical Consequences of the Adult Growth Hormone Deficiency
The main clinical features of adults with the growth hormone deficiency relate to the body composition, physical performance, and good psychological being. Body composition is often significantly altered with an increased fat, predominately abnormal fat, and decreased in muscle mass, which in turn translates to reduced muscles strength and exercise capacity. People that also have a deficiency with weight control will experience even more struggles with weight loss.
Psychological well-being may also be affected and impaired which may be seen as depressed moods and increased anxiety levels. These clinical consequences leave the growth hormone deficient adults disadvantaged both physically and psychologically.
Treatment of Adult Growth Hormone Deficiency
Research has shown that adult growth hormone replacement have consistently shown significant beneficial effects. Growth hormone replacement reduces total body fat and in particular fat around the midsection- more specifically around the abdomen. It is also lean body and muscle mass, which improves strength and exercise tolerance. Physical fitness is increased which appears to be related in part to an improvement in cardiac function. General well-being is also seen to be greatly enhanced which positively influences the overall quality of life and personal productivity.
When treated for growth hormone deficiency, the growth hormone is administered as a daily injection similar to those that suffer from diabetes with self-administered insulin. Some side effects are possible relating to the growth hormone injections to the replacement therapy. The side effects are most commonly mild and chiefly related to fluid retention. Other commonly reported side effects of the treatment include: muscle aches, joint discomfort swelling of the hands and feet and headaches. All of these side effects are transient and respond to a reduction in growth hormone dose.
As a result of benefits experienced by the growth hormone deficient adults, the growth hormone for adults use has been registered in Europe, United Kingdom, New Zealand, the United States and Brazil. In Australia, the growth hormone is registered for use in children with the growth hormone deficiency. Its use in adults is currently under review.
Growth hormone deficiency is being increasingly recognized as a result as a cause of premature mortality. Over the last decade, much of the understanding of clinical presentations of the growth hormone deficiency had improved. The documented benefits of growth hormone replacement therapy have helped improve the quality of life of many patients that live with adult growth hormone deficiency. Growth hormone deficiency replacement is well tolerated by many patients. The long-term fears of tumor reoccurrence or re-growth have not been confirmed by most observational studies and until proven otherwise. The growth hormone therapy should be routinely prescribed and titrated to reap clinical benefits.