By Dr. Dimitar Marinov

medical reviewed by Best HGH Doctors and Clinics dedicated team.

Evidence basedThis article is reviewed by medical professionals for the relevancy and accuracy of the content. Every article is evidence-based and contains references to peer-reviewed studies and academic research.

The human growth hormone (HGH) is essential for the regulation of your metabolism, body composition, and even the function of your heart. Despite its levels naturally declining in adults, HGH deficiency can have serious health consequences for your health.

We will reveal all about the current scientific understanding of adult growth hormone deficiency, how to test it, and what are the main symptoms and causes.

Get your hormones tested

What is growth hormone deficiency?

HGH (also called somatotropin) has a well-known role in stimulating growth and development in children. It is produced by a small gland located at the base of the brain that is responsible for the production of several other hormones as well.

The levels of HGH peak during puberty and then progressively decline. However, even after a person’s growth is complete it has a major role in optimal wellbeing. Here is a comparison table of the normal growth hormone levels by age.

Normal growth hormone levels by age

Growth hormone deficiency (GHD) in adults is a well-known condition that affects about 1-3 people per 10 000 according to scientists. This is a rare deficit caused by inadequate production of somatotropin by the pituitary gland.

Despite its rarity, GHD can lead to serious complications in adults. The hormonal balance in the human body is a delicate equilibrium, and affecting one of its elements can disturb multiple metabolic processes.

If the condition is left untreated, GHD can lead to severe health problems in adults such as osteoporosis, increased risk of atherosclerosis, diabetes, heart disease, and eventually premature death

How to test and diagnose growth hormone deficiency in adults?

Unfortunately, the diagnosis of adult-onset GHD is not as simple as taking a blood sample and testing it for GH levels. A single measurement of GH levels is not informative because the hormone has an episodic (pulsatile) secretion.

This means that the growth hormone levels fluctuate throughout the day and go through various stages of peaks and falls. Growth hormone levels can be undetectable in adults during periods when they naturally plummet and this is still not an indicator of GHD.

How to test adult growth hormone deficiency

Instead, multiple sampling of HGH levels throughout the day would be ideal for the diagnosis but it is not practical at all. This is why the diagnosis of adult-onset GHD involves stimulation tests that provoke a peak HGH release. Various drugs and hormones can be used for the procedure but the gold standard is performing an insulin tolerance test (ITT).

The hypoglycemia caused by ITT results in the stress response of the organism and an increased synthesis of the insulin’s counterregulatory hormones. The human growth hormone is one of them.
The growth hormone deficiency test has certain risks, which is why there are specific contraindications against it, including:

  • Age above 60 years
  • Ischemic heart disease
  • Epilepsy
  • Severe panhypopituitarism or adrenal insufficiency
  • Hypothyroidism

If the patient has some of the contraindications, then there are other options for diagnosis such as glucagon and Growth hormone-releasing hormone (GHRH) tests.

Growth hormone stimulation test protocol

The tests should be performed only in experienced endocrine units where such procedures are frequently performed and a strict protocol is followed.

Here is an example of such a protocol.

First of all, you need to prepare for the procedure by fasting (water is permitted) overnight and skipping breakfast in the morning. Right before the test, you have to undergo an ECG procedure and weight measurements. The doctor will carefully explain to you the side effects which you will experience, such as sweating and palpitations.

They are caused by the injection of insulin which induces hypoglycemia by lowering blood glucose levels under 2.2 mmol/l (40 mg/dl). You will have to be recumbent during the test. One stimulation with ITT is sufficient for the diagnosis of adult GHD.

During the test, you will be repeatedly drawn blood for GH levels monitoring and the normal peak value should be above 7 ng/ml. However, if your HGH response is below 3  ng/ml, this indicates that you have GHD.

What are the symptoms of growth hormone deficiency?

Low GH levels in adults have typical but nonspecific symptoms which significantly complicates the diagnostic process. GHD affects multiple organs and metabolic processes and the following symptoms are quite common:

Weight gain

Increased body fat is the most common physical symptom of growth hormone deficiency. Adult-onset GHD is associated with a typical pattern of weight gain called a central type of obesity. Central means that fat accumulation is mainly focused around the abdominal area.

Central obesity always involves the accumulation of fat around the internal organs, called visceral fat

This type of fat releases high levels of free fatty acids and inflammatory molecules in the bloodstream which leads to multiple metabolic problems, including diabetes and atherosclerosis.

Decreased muscle mass and strength

HGH is an anabolic hormone for protein metabolism with a protective effect against muscle loss. This is why its deficiency leads to a negative change in body composition and the decrease in muscle mass and strength is well documented in studies with GHD patients.

While fat tissue increases and accumulates around the abdomen, muscle tissue slowly wastes away.

Some trials have suggested that even respiratory muscles become weakened and lung function is often impaired in patients with HGH deficiency.


Multiple studies have revealed that the lack of growth hormone leads to lower bone mineral density and results in osteoporosis. The reduction in bone density is also related to the reduction in skeletal muscle mass.

This leads to an increased risk of broken bones including vertebral fractures in adult patients with growth hormone deficiency.

Low energy levels and fatigue

The levels of fatigue in GHD are often so elevated that they impair the patient’s wellbeing and quality of life. This is related to the effects of GH on thyroid hormones and overall metabolism. Usually, these physical symptoms are coupled with physiological ones such as depression and anxiety.

Increase in LDL-cholesterol and related heart problems

Studies report elevated levels of bad cholesterol (LDL) and a decrease in good cholesterol (HDL) in 26–45% of GH-deficient adults. The disturbed lipid profile in combination with the worsened body composition and insulin sensitivity leads to an increased risk of atherosclerosis and heart problems in patients with GHD.

What causes growth hormone deficiency in adults?

Several causes can lead to growth hormone deficiency. Depending on these factors we can classify the condition into three main types:

Congenital growth hormone deficiency

This is a type of GHD that is present since a child’s birth. It results from either birth defects in the brain or genetic mutations. This condition does not affect the growth of the fetus or the newborn but after the baby is a few months old, the most evident symptom is poor growth and short height for the age of the child.

Idiopathic growth hormone deficiency

This type of GHD usually has its onset in childhood. The term idiopathic means that the cause is unknown. Once again it results in poor growth and maturation of the affected child. Adult-onset idiopathic GHD is extremely rare.

Acquired growth hormone deficiency

Acquired deficiency is common in both cases of childhood and adult-onset GHD. It always has a specific identifiable cause that has occurred after birth. The growth hormone deficiency causes include pituitary tumors, severe head trauma, radiation or surgical treatment, infection, or infarction of the pituitary gland.

Almost all cases of GHD with adult-onset are acquired. The most common cause is benign pituitary tumors such as adenomas or craniopharyngiomas. They contribute to about 57% of all cases of GHD in adults according to data from KIMS – the multinational, pharmaco-epidemiological surveillance database for adult hypopituitary patients.

What is the best treatment for GHD?

The best treatment for growth hormone deficiency in both children and adults is HGH replacement therapy. The treatment requires subcutaneous HGH injections once a day. You can inject them on your own or with the help of a family member.

Doctor shows how to inject HGH

If you have the indications for starting a growth hormone deficiency treatment the initial dose will be as low as 0.2 mg of HGH. Thanks to the low dose approach the side effects of modern HGH therapies are rare.

If the initial dose is bigger, then there is a risk of rapid correction of the sodium and water balance in the body. This can lead to edemas, pain in muscles and joints, and persistent severe headache due to raised intracranial pressure.

There have been concerns that HGH therapy and IGF-I might increase the risk of tumor formation related to either new tumors or regrowth of pituitary adenomas. IGF-I is also a hormone and its secretion depends on the HGH levels.

However, extensive studies with hundreds of patients on HGH therapy do not indicate an increased risk of neoplasia or pituitary and parasellar tumor regrowth.

According to the effects on IGF-I and the improvement in GHD symptoms, your doctor will review the dosage every couple of weeks and increase it if necessary until you can achieve IGF-I levels typical for your current age.

One of the first benefits you will notice from HGH therapy is more muscle mass and less abdominal fat. The effects of HGH therapy also involve lowering LDL cholesterol, improving bone mineral density, and reversing osteoporosis. The quality of life is also significantly improved in all patients according to trials.

How growth hormone deficiency affects life expectancy?

If a growth hormone deficiency is left untreated, it can shorten the patient’s life. Nationwide studies performed in Denmark have revealed that people suffering from GHD have significantly increased mortality compared to the healthy population.

The main causes of death were heart problems and cancer. A significant contributor to their occurrence is the increased amount of visceral fat related to GHD. On the other hand, scientists have further investigated the mortality in people after HGH replacement therapy and they have found that it is significantly reduced compared to mortality in those left untreated.

Growth hormone deficiency is a serious condition that can lead to reduced quality of life and premature death. It affects your mood, body composition, energy levels, heart, and bone health.
This is why we at Best HGH Doctors and Clinics have a team of highly experienced doctors and endocrinologists and we will treat you with exceptional care and dedication.