How Do You Want to Grow?
Growth hormone supplementation has been widely publicized lately due to recent allegations against Jason Grimsley and David Segui of Major League Baseball fame. People choose to take the supplement for a promise of augmented athletic performance or to turn back the clock on life, without chance of detection by governing agencies. Before jumping on the bandwagon, you should know what growth hormone is and what its effects are.
What is Growth Hormone?
The polypeptide human growth hormone, hGH, is one of the most important naturally occurring hormones for normal growth to adult size. It is normally secreted in a pulsatile fashion 6-12 times per day1, meaning concentrations fluctuate throughout the day. Growth hormone secretion peaks during puberty and decreases with age. Secretion is increased by sleep, stress, starvation, puberty, exercise, hypoglycemia (low blood sugar), and other hormones (ie growth hormone releasing hormone).
hGH secretion is inhibited by somatostatin (from the hypothalamus), somatomedins (hormones released by the hGH target organs in response to a rise in hGH), obesity, hyperglycemia (high blood sugar) and pregnancy. It is important to understand that like many other hormone systems in the body, hGH and GHRH inhibit their own secretion as part of a negative feedback system.
What is the effect of Growth Hormone?
hGH is taken up by skeletal muscle6 and has many effects. It acts directly to decrease glucose uptake into cells, increase hepatic gluconeogenisis10, increase lipolysis (fat release from adipose cells)11, increase protein synthesis in muscle cells7,8,9, increase lean body mass and increase release of insulin like growth factor (IGF-1) from the liver and locally in skeletal muscle. IGF-1 increases bone length in children, increases protein synthesis in muscle and increases lean body mass. Both growth hormone and IGF-1 are anabolic, non-androgenic compounds. This means that it promotes protein synthesis without stimulating male secondary sex characteristics.
Are there diseases of Growth Hormone secretion?
Yes. A deficiency in hGH can result in failure to grow and mild obesity. Currently the FDA has approved growth hormone therapy in the treatment of childhood growth deficiencies and wasting diseases such as AIDS24.
There are also diseases of excess growth hormone secretion. Excess hGH before puberty can cause gigantism and after puberty causes an increase in bone growth, organ size and glucose intolerance2.
How can I increase my levels of hGH?
As already mentioned, exercise can naturally increase growth hormone secretion. Research has shown that exercise counteracts the negative feedback mechanisms of GHRH and hGH allowing levels to rise unchecked by this feedback system5. Research has also shown that repeated exercise sessions led to an increase in hGH after each session and over a 24 hour period. Results suggest that load and frequency of the resistance exercise are important determinants of hGH concentration while length of the work out is not13,14.
Over the short term, endurance exercise also increases growth hormone release. Significant increases in plasma growth hormone was noted after 10 minutes of exercise above the lactic acid threshold (ie high intensity). Multiple exercise sessions further increased the amount of growth hormone released per pulse rather than leading to feedback inhibition17. However, in response to chronic endurance exercise (greater than 3 weeks), some studies found a decreased growth hormone response to additional exercise bouts18,19,20. This suggests that the hGH response to endurance exercise is adaptive and may plateau with time.
Can growth hormone supplementation help me as an athlete?
Athletes have taken interest in exercise induced growth hormone release since it has been suggested that hGH mediates muscle growth. In addition, hGH may affect energy utilization and oxygen use during exercise. To start, hGH administration has improved exercise capacity in individuals with the diseases of cardiomyopathy and cystic fibrosis3,4. It is possible that this effect is due to the inability of these ill individuals to exceed exercise thresholds for exercise induced hGH.
Evidence for growth hormone supplementation to augment skeletal muscle strength and size is inconclusive at this point. Basically, research has arrived at two opposing points. That hGH supplementation may give an anabolic advantage, but without any increase in power or metabolic advantage for athletes. This is saying that at the molecular level, they have found that hGH has shown a benefit, but when put to the test, no increase in strength was found.
In a double blind study with 15 healthy men and 15 women over a 28 day period, researches found no benefit of growth hormone supplementation on power output or oxygen consumption on endurance bicycle exercise21. The author suggests that administration of supra-physiologic growth hormone may suppress endogenous exercise stimulated growth hormone secretion. This may be able to explain why growth hormone administration in deficient individuals can augment exercise performance and growth without a similar benefit for athletes. Similarly inconclusive results have been found in studies focusing on resistance training25,26,27.
On the other hand, it has been shown that growth hormone supplementation in endurance trained athletes has a net anabolic effect28. The amount of growth hormone administered was 4.7 mg per day for an approximately 150lb man. The IGF-I blood concentration was found to increase approximately four times normal levels. Although they found an anabolic effect, the results were not correlated with improvements in strength or performance.
What Are Manufacturers Trying to Sell Me?
This is about as clear as the current research on the subject. Many supplements marketed as “growth hormone” are actually substances that theoretically stimulate secretion of growth hormone. Examples include levodopa (prescription to treat parkinson's disease), clonidine (prescription anti-hypertensive) and the amino acids arginine, ornithine, lysine and tryptophan. Large doses of these amino acids must be administered intravenously to elucidate any significant increase in growth hormone however. However, nutrition supplement stores tend to sell these as oral supplements. Digestive system absorption isn't capable of achieving blood levels necessary to produce an effective increase in GH levels. And the natural negative feedback system will likely counteract this effect making a long term increase in growth hormone unlikely22.
Furthermore, of the supplements that are actually supposed to contain growth hormone, no regulations or standards exist to verify quantity and purity of product. Regulated growth hormone can be obtained through a physician, with a cost in the range of a thousand dollars per month. This makes me wonder why companies selling growth hormone as nutritional supplements are content charging $40 per month for unverified contents when they could be making thousands of dollars per month for product with verified contents. This leads me to believe that an independent lab would find the nutritional supplement bottles don't contain what they say they do.
Growth hormone effect on aging.
Current research presents conflicting information on the use of growth hormone for its anti-aging effects. Also some of the strongest supporting evidence comes from studies that are not peer reviewed, double blinded or randomized, making its support questionable.
As already mentioned, growth hormone concentrations naturally decline with age. As a result some doctors are currently using growth hormone regimens off label, for a use not approved by the FDA. With a price tag of between $1,000 and $2,000 per month, you must carefully weigh the possible benefits of enrolling in one of these anti-aging programs against price24. Often, the amount of growth hormone administered in these programs is lower than the amount found efficacious by even the poor quality studies24.
What are the possible side effects?
Growth hormone supplements, even if pure, aren't going to have just the one or two positive effects that you want, there will be many effects throughout the body. The abuse of growth hormone has been associated with arthralgia, arthritis, cardiomegaly, muscle weakness, hyperlipidemia, impaired glucose regulation, risk of type I diabetes and impotence12. As you have already read, growth hormone stimulates the secretion of IGF-1. High levels of this hormone have been correlated with an elevated cancer risk23. So at this point you should be weighing the unsubstantiated benefit of growth hormone supplementation in athletes against the substantiated serious health risk associated with its use. After rationally looking at the data, I don't think anyone would recommend its use unless to treat a serious medical condition diagnosed and followed by a medical doctor. I do not suggest you using this product yourself.
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