The GH/IGF-1 axis is a major hormonal system in the human body. It is responsible for stimulating growth in children, as the levels of HGH and IGF-1 gradually increase in childhood and peak during puberty.
This coincides with the pubertal growth spurt.
As adults, IGF-1 levels decrease over time, but they are still produced when needed in response to the hormone HGH. This is important for the maintenance of bone mass, muscle mass, and tissue hypertrophy, as well as for the healing process.
Optimal IGF-1 Levels by Age and Gender
Maintaining balanced IGF-1 levels is key for good health and a long life. If IGF-1 levels drop too low, it can cause a range of health issues such as bone loss, slower healing after injuries, muscle weakness, and decreased performance.
On the other hand, an overabundance of IGF-1 can lead to acromegaly, a condition characterized by abnormal growth of the hands, feet, and face, and a shortened life expectancy. Therefore, it is important to ensure that your IGF-1 levels are in the normal range to maintain optimal health and wellbeing.
The amount of IGF-1, in adults varies depending on their age. Studies of children, adolescents and adults have determined optimal IGF-1 levels for each age group. Generally speaking, the levels of IGF-1 will increase with age, but the exact amount can vary.
For instance, in children, the optimal IGF-1 level is between 80 ng/ml and 400 ng/ml, while in adults, the optimal IGF-1 level is between 70 ng/ml and 300 ng/ml. There is no single cut-off point for normal IGF-1 levels in adults, as the ideal level of the hormone can vary from person to person.
How to test IGF-1
A blood sample is necessary to accurately measure your IGF-1 levels. This involves visiting a lab, where a healthcare professional will use a needle to draw a small amount of blood from your arm. The whole process is usually quick and painless, but it is important to inform the healthcare professional if you have a history of fainting during such procedures or if you have any problems with your coagulation.
There is no need for any special preparation for the test, except for avoiding biotin supplementation as it can interfere with the results. For more precise measurements, mass spectrometry can be used, although it is more expensive.
A doctor may order an IGF-1 test to check for growth hormone deficiency (GHD). This test is used because IGF-1 levels in the body correspond to the average HGH levels.
Testing HGH directly is not very helpful because it can fluctuate a lot, whereas IGF-1 levels tend to stay stable. It is important to note that normal IGF-1 levels do not necessarily rule out GHD.
Low IGF-1 levels can also be caused by growth hormone insensitivity (Laron’s syndrome) or liver cirrhosis. The liver is the main organ that releases IGF-1 into the blood in response to HGH, so if the liver is damaged, IGF-1 levels will be low.
Normal IGF-1 levels by age
It is evident from the table that gender has no significant impact on IGF-1 levels. During puberty, these levels reach their peak and then gradually decline as an individual advances into adulthood.
This is in line with the Human Growth Hormone (HGH) levels in the body. The surge in GH/IGF-1 levels also corresponds to the fast growth and development which occurs during puberty.
For children and adolescents, having adequate GH and IGF-1 levels is essential for achieving their final height. Aside from this, other factors such as genetics, diet, physical activity, body weight, and body composition can influence IGF-1 levels in adults. All of these variables can affect the amount of IGF-1 present in the body, which in turn affects the individual’s overall health and wellbeing.
Growth is generally considered to be complete after puberty, but optimal IGF-1 levels still play an important role in adult life, helping to support muscle hypertrophy, tissue regeneration and bone mineral density.
Aside from age, various other factors can affect IGF-1 levels in adults, such as genetics, diet, physical activity, body weight and composition.
Studies have shown that Caucasian and African-American people tend to have higher IGF-1 levels than Mexican-American individuals.
Additionally, being overweight or obese can lead to reduced IGF-1 levels, with a 35% decrease observed in obese individuals compared to those of normal weight. Moreover, losing a substantial amount of weight can also result in a 40% increase in IGF-1.
Fasting or inadequate protein intake can also cause a decrease in IGF-1 levels, as the hormone FGF21 is released, which reduces the stimulation of HGH on IGF-1 production.
How can low or high IGF-1 affect your life?
An imbalance of IGF-1 can have different effects depending on a person’s age. In children, low IGF-1 levels can lead to stunted growth and short stature, usually due to a deficiency or insensitivity to growth hormone.
In adults, low IGF-1 levels can cause muscle wasting, reduced bone mineral density, slower healing of injuries, and an increased risk of fractures.
An excess of IGF-1, usually caused by a pituitary tumor, can lead to an overproduction of growth hormones, which can cause excessive body fat gain, reduced energy levels, and an increased risk of cardiovascular diseases.
In children, an excess of growth hormones and insulin-like growth factors (GH/IGF-1) is a very rare occurrence and can result in gigantism, a condition that is characterized by excessive growth and body height much higher than the average. People with gigantism typically have long limbs and torsos.
In adults, an overabundance of GH/IGF-1 leads to acromegaly, a condition that does not affect the height of the patient, but instead causes an increase in the thickness of bones and cartilage. This leads to physical changes in the face and skeleton, such as a larger nose, lips, and tongue; protruding brows and lower jaw; and wider feet, hands, and fingers.
Patients who suffer from an excess of growth hormone (GH) and insulin-like growth factor 1 (IGF-1) may experience a range of health issues including high blood pressure, arthritis, insulin resistance, and a shorter life expectancy.
Diagnosing IGF-1 deficiency and Treatments
To accurately diagnose and treat the condition, a provocation test such as an insulin tolerance test is required. When GHD is confirmed, the patient can be prescribed daily injections of recombinant HGH which can be successful in managing the symptoms.
Additionally, lifestyle adjustments may be recommended, such as dietary changes and regular exercise, to further help manage the condition and improve overall health.
If you suffer from Laron syndrome which has caused low IGF-1 levels, then HGH therapy is not the best option for treatment. Instead, recombinant IGF-1 and IGFBP3 injections are prescribed to manage the condition.
For those who are healthy, the best way to increase IGF-1 levels is to maintain a healthy weight, avoid fasting or protein restriction, and exercise regularly.
If abnormally high IGF-1 levels are detected, then an HGH test and MRI will be ordered to look for a hormone-secreting pituitary tumor. If a tumor is found, it can be treated through surgery, radiation, or medications. However, this treatment can cause hypopituitarism, which may require HGH therapy to manage the symptoms of growth hormone deficiency.