What Do We Really Know About Risks and Benefits of Growth Hormone & IGF-1?: Injections, Secretagogues, and Testing

What Do We Really Know About Risks and Benefits of Growth Hormone & IGF-1?: Injections, Secretagogues, and Testing

Insulin-like growth factor type I (IGF-1), also called somatomedin C, is thought to be the best known indicator of growth hormone release from the pituitary gland. With a half-life of about 20 hours, compared to the 20-minute half-life of human growth hormone (hGH), IGF-1, which is stimulated by the release of hGH, provides an assessment of daily growth hormone release. Upon investigating the variety of clinical aspects of IGF-1, one of four known somatomedins, the consensus among clinicians and testing experts seems to be that IGF-1 assessment is not as straightforward as it was once thought to be. Although hGH acts on cells directly, most of its growth promoting effects are elicited through IGF-1, which has a mitogenic effect on prostate and other cells, making it the subject of studies to examine its role in the development of prostate and other cancers. The inherent increase in IGF-1 that occurs with the use of recently popularized hGH injection and secretagogue therapies, warrants a closer look at the role of IGF-1 in the management of prostate specific antigen (PSA) and other cancer markers, hormone replacement therapy, and general symptoms associated with aging.


A study published recently in the journal Science, suggests a relationship between high levels of IGF-1 and prostate cancer, based on IGF-1 measurements taken an average of seven years before the diagnosis of prostate cancer and not at the time of diagnosis. In order to draw definitive conclusions about the role of growth hormone and IGF-1 in prostate cancer, it is important to look at the effects of hGH therapy on prostate cancer patients as well as the relationship between changes in IGF-1 and PSA. In a paper titled Insulin-Like Growth Factor-1 Blood Levels Are Not Associated with Prostate Specific Antigen Levels or Prostate Cancer: A Study of 749 Patients, L. Cass Terry, MD, PhD, PharmD, points out that the incidence of prostate cancer increases with age, at the same time that IGF-1 levels are significantly declining. Dr. Terry goes on to demonstrate the lack of correlation between IGF-1 levels and PSA in this sample of 749 men, many of whom were receiving recombinant human g rowth hormone (rhGH) replacement therapy. Of the patients who exhibited high PSA levels (median = 6 times higher than controls) there was no significant difference in IGF-1, and in six cases of known prostate cancer, patients exhibited IGF-1 levels in the lowest quartile. In addition, Dr. Terry points out that there was no increase in prostate cancer, or other malignancy, in 3,000 patients who were treated with long-term rhGH.

Dr. L.E. Dorman, co-author of Growth Hormone: Reversing Human Aging Naturally, notes that IGF-1 is produced by cancer cells as well as cells of the immune system, which are stimulated in the presence of cancer,"all of the evidence that we have indicates that IGF-1 is supportive to the immune system. In treatment with oral hGH secretagogue therapy I have observed a consistent lowering of PSA."


When asked whether IGF-1 testing could be used as an independent marker for breast or prostate cancer risk, Allan Broughton, MD, Director of Antibody Assay Laboratories (AAL), responds, "I think that's nonsense." Dr. Broughton, who developed the first commercially available IGF- 1 test nearly two decades ago, points out that monitoring IGF-1 levels during the course of growth hormone therapy may be important in avoiding excess levels of IGF-1 and suggests an upper limit of 250 ng/dl. "We have to realize that there may be a reason that IGF-1 levels decline with age...there is a lot that we don't know about the effects of excess IGF-1."

Arnold Segredo, MD, PhD, of the Life Xtension Institute, points out that "IGF-1 may not be a true marker for aging or cancer, but it appears to be an important variable in interpreting a larger spectrum of tests. We perform an entire hormone panel, including PSA in men. Depending on the initial values, we look for changes in IGF-1 and other hormones over the course of hormone therapy." Dr. Segredo, who promotes the use of rhGH as well as Symbiotropin, an hGH secretagogue, offers guidelines for testing, treatment and monitoring that have demonstrated effectiveness in maintaining IGF-1 levels within a physiologic range, pointing out that the secretagogue, "seems to modulate IGF-1 levels, keeping them from becoming too high. An effective protocol involves modulation of IGF-1 and concurrent monitoring of other co-factors, such as PSA." Dr. Segredo points out the importance of more frequent monitoring in patients with initially high (>200 ng/dl) IGF-1 levels, suggesting that IGF-1 le vels may fluctuate dramatically at the onset of therapy, then stabilize after three months. Once target IGF-1 levels are reached, Segredo recommends monitoring IGF-1 levels every six months. (Table 1)

Table 1

Initial IGF-1






30 days



60 days



90 days

rhGH &


Dr. Dorman, who has been involved in clinical research on Symbiotropin notes the lack of correlation between IGF-1 levels and symptomatic improvement, "Initially we see a general rise in IGF-1, an average of 33% in the first 90 days, then we frequently see decreases and fluctuations in the following months. At first, we tried to drive the IGF-1 levels back up by increasing the dose, but we quickly realized that symptoms continued to dramatically improve, despite the drop in IGF-1." Dr. Dorman reports the following results:

% Reported Improvement after

3 months of Symbiotropin

(39 Patients)

Endurance and Body Composition

Muscle Strength


Muscle Size


Fat Reduction


Overall Energy


Exercise Tolerance


Exercise Endurance


Hair and Skin

Skin Texture


Skin Thickness


Skin Elasticity


Wrinkle Disappearance


New Hair Growth


Healing and Immunity

Healing of Old Injuries


Healing of other Injuries


Healing Capacity


Back & Joint Flexibility


Resistance to common Illness


Sexual Function

Sexual Potency/Frequency


Duration of Penile Erection


Frequency of Nighttime Urination


Mental Function

Mental Energy and Clarity


Emotional Stability


Attitude Toward Life




hGH Interaction With Other Hormones

Growth hormone interacts with all other hormones, which requires us to generally broaden the scope of our approach to hormone replacement therapy. There are concerns about interaction with insulin, thyroid hormone, and sex hormones. Specifically, rhGH therapy is regarded as a contraindication in diabetic patients, while data points to Symbiotropin as a profound modulator of insulin -- consistently lowering insulin requirements in diabetics. Dr. Segredo points out the similarity of IGF-1 to insulin with respect to transport of glucose: "There seems to be a threshold of IGF-1 where insulin requirements drop significantly." He refers to a patient whose insulin requirements did not change throughout the initial four months of treatment, during which time his IGF-1 levels were raised from 123 to 189, but in the fifth month when his levels reached 211, insulin requirements dropped significantly. Notably, the patient's insulin requirements have continued to drop while his IGF-1 levels have stabilized around 200.

Dr. Daniel Rudman, a pioneer in growth hormone research, concluded that the decrease in one hormone, causes its target gland(s) to decrease the production of its own hormone(s). According to Dr. Segredo, "the greatest thing about our experience with hGH therapy, is that we now know that the reverse is true. The increase in the release of one hormone [growth hormone] signals the increase in the production of all other hormones accordingly. In every, patient we have observed a rise in all hormones, which is directly proportionate to the rise in IGF-1. This does not occur with exogenous hGH."


It seems that the best approach to hGH therapy is a conservative one that does not provoke excess levels of IGF-1. This may be accomplished with secretagogues that serve to modulate IGF-1, the discretionary use of rhGH, and through the sharing of clinical data. In order to support the growth of our knowledge base in a way that is proportionate to the demand for hGH therapy, Michael Walerstien of Anti-Aging Associates, notes the important role of his organization in "centralizing our independent associate physicians' data from around the country in order to develop and disseminate anti-aging protocols so that the individual physician and patient can directly benefit from the knowledge of the whole."

Physicians may request an application for affiliation with Anti-Aging Associates by calling 1-888-381-3858, or writing Anti-Aging Associates 4699 N. Federal Hwy. Ste 105-C, Pompano Beach, FL 33064.

Pharmacologist James Jamieson is the co-author of Growth Hormone: Reversing Human Aging Naturally, The Methuselah Factor (published by LNN, $12.95)

Townsend Letter for Doctors & Patients.


By James Jamieson

Share this with your friends