I have to admit I was impressed with Sylvester Stallone's appearance in his recent interview with Joe Rogan. The 61-year old actor is currently promoting his new Rambo film. His notable muscular appearance seemed less impressive to me when Mr. Stallone told Time Magazine of his use of hormonal supplements as a performance enhancer. "HGH (human growth hormone) is nothing?Anyone who calls it a steroid is grossly misinformed." Stallone further went on to comment that he believes use of HGH will soon be available over the counter.
Recently, celebrities like 50 Cent and Mary J. Blige have also reported HGH use.
The truth of the matter is that while human growth hormone is not a steroid, that fact does NOT mean that it comes free of risks. Serious side effects of HGH use include an increased risk of developing diabetes, heart problems and cancer.
In clinical environments, synthetically made growth hormone is used to treat both children and adults with severe growth hormone deficiencies. HGH functions by stimulating the release of insulin-like growth factor-1 (IGF-1). The main metabolic effects observed from HGH use include an increase of uptake of glucose (the major carbohydrate used by our bodies), and increase in the creation of proteins. This enhancement of protein building is one of the reasons why this supplement is used to try to promote muscle growth and development. 
Nowadays, HGH is the main doping agent of choice in the sports world. It attracts use because of its availability and because of the fact that it is not a steroid. Various side effects have been observed in both HGH treated patients and athletes. The following is a list of major risks associated with this hormonal supplement. 
* Intracranial hypertension (elevated pressure in the skull)
* Visual changes
* Myalgia (muscular pain)
* Peripheral edema (swelling of lower limbs)
* Carpal tunnel syndrome
* Arthralgia (joint pain)
* Increased growth of nose and jaw
* High blood pressure
* Increased diabetes risk
* Increased cardiovascular risk
* Increased cancer risk (colon cancer, breast cancer, prostate cancer)
Even clinical patients using prescribed hormones and growth factors as replacement therapy have an increased cancer risk. This risk is likely to be much higher in casual users of HGH since to see the desired performance enhancing effects, high doses over longer periods of time need to be injected.
Animal studies have shown that high doses of HGH can induce tumor formation in rats. Clinical studies have revealed that patients who have high levels of IFG-1 have an increase in diagnosis of malignant colon tumors. Women with breast cancer also have elevated growth hormone levels.
Long-term studies have been conducted on patients treated with growth hormone in childhood and early adulthood. The studies clearly show that these individuals with hormonal treatment had a greater incidence of colorectal cancer and Hodgkin lymphoma.
Even patients treated with hormones as replacement therapy to rebuild normal levels showed an increased risk of colorectal cancer.
There is also an overall increase in death rates for patients who are prescribed hormones as treatment. 
Both laboratory and clinical studies ultimately support the theory that both growth hormones and IGF-1 increase cancer risks. Evidence is not conclusive about whether or not these supplements influence cancer that has already developed.
In addition to the cancer risks, the potential cardiovascular side effects need to be addressed. Premature coronary artery disease has also been reported with HGH use.  All of the side effects mentioned above may contribute to the occurrence of different types of abnormal heart rhythms.
Because of the fact that HGH causes the liver to produce IFG-1, taking synthetic IGF-1 will have similar adverse side effects to taking HGH.
Any additional questions about hormonal therapies should be discussed with your own personal physician.
1. Tentori, L., & Graziani, G. (2007). Doping with growth hormone/IGF-1, anabolic steroids or erythropoietin: is there a cancer risk? [Review]. Pharmacological Research, 55(5), 359-369.
2. Takala J, Ruokonen E, Webster NR, Nielsen MS, Zandstra DF, Vundelinckx G, Hinds CJ. Increased mortality associated with growth hormone treatment in critically ill adults. N Engl J Med 1999; 341:785?792
3. Furlanello, F., Serdoz, L. V., Cappato, R., & De Ambroggi, L. (2007). Illicit drugs and cardiac arrhythmias in athletes. [Review]. European Journal of Cardiovascular Prevention & Rehabilitation, 14(4), 487-494.