The most honest answer to the question about the long-term risks of hexarelin is this: no one has systematically studied them. However, this does not mean that nothing can be said about them. There are data on long-term stimulation of the growth hormone axis by other means, epidemiology of IGF-1, experience with excess growth hormone in acromegaly. The editors have compiled this knowledge to show where the reasonable fears lie and where the gaps lie.
Why there are no long-term data
The long-term safety of a drug is evaluated in large clinical trials lasting a year or more, followed by post-marketing follow-up of thousands of patients. Hexarelin did not reach this stage: its development as a drug stopped at the level of phase I–II studies and physiological experiments.
The longest human studies, as far as the editors know, lasted several months. They focused on the hormonal response and noted, in particular, the development of tachyphylaxis. Scientific literature is silent about the consequences of long-term use - even with breaks.
Lack of data is often misinterpreted as “lack of risk”. In reality, it only means that the risks are unknown. Rare or delayed complications, such as cancer or cardiovascular disease, may take years to manifest and be seen only in large groups of people.
Therefore, to assess long-term risks, one has to rely on indirect sources: knowledge about the physiology of growth hormone and IGF-1, research on other ghrelin receptor agonists, and states of natural growth hormone excess. Such an approach does not provide precise answers, but outlines areas of reasonable concern.
Glucose metabolism and insulin resistance
Growth hormone is a counterinsular hormone: it increases the production of glucose by the liver and reduces its assimilation by muscles. With a short increase, this is a physiological response, but chronic stimulation can impair insulin sensitivity.
This risk is best illustrated by a study of another ghrelin receptor agonist, oral ibutamoren (MK-677). In a two-year randomized study by Nass et al (2008) in healthy older adults, the drug increased growth hormone and IGF-1 and increased lean body mass, but at the same time modestly increased fasting glucose and decreased insulin sensitivity.
Hexarelin is a different molecule with different pharmacokinetics, and it is incorrect to directly transfer these results to it. However, a common mechanism—stimulation of the ghrelin receptor and the growth hormone axis—makes a similar effect on glucose metabolism biologically plausible.
For people who are overweight, have prediabetes, or have a genetic predisposition to type 2 diabetes, this is potentially the most significant long-term risk. Paradoxically, these are the people who often look for "fat burning peptides."
IGF-1 and the issue of cancer risk
IGF-1 is a powerful growth factor that stimulates cell division and inhibits cell death. These properties are necessary for normal growth and regeneration of tissues, but in theory they can contribute to the development of neoplasms.
Epidemiological data support this hypothesis. A meta-analysis by Renehan et al. (2004) published in The Lancet showed an association of higher IGF-1 blood concentrations with an increased risk of certain types of cancer, particularly prostate cancer and breast cancer in premenopausal women. This is an association, not a proven causal relationship, but it is taken into account in clinical practice.
Another landmark is acromegaly, a condition of chronic excess growth hormone due to a pituitary tumor. Patients with acromegaly have been described to have an increased incidence of colonic polyps, as well as cardiovascular and metabolic complications. Of course, growth hormone levels in acromegaly are usually much higher and more stable than would be expected from secretagogues.
| Data source | What it shows | Relevance to hexarelin |
|---|---|---|
| Epidemiology of IGF-1 | Association of high IGF-1 with certain types of cancer | Indirect: the peptide raises IGF-1 less strongly and less consistently |
| Acromegaly | Consequences of long-term growth hormone excess | Extreme scenario model |
| Long-term studies of ibutamoren | Effect of ghrelin receptor agonist on glucose | Shared mechanism, different molecule |
| Studies of hexarelin itself | Hormonal changes, tachyphylaxis | Direct, but lasting up to several months |
Practical conclusion: for people with a history of oncological diseases, precancerous conditions, or burdened heredity, any artificial increase in growth hormone and IGF-1 without medical indications is particularly unreasonable. For recombinant growth hormone, an active malignant tumor is a contraindication in the official instructions.
Heart, blood vessels and hormonal axes
The effect of hexarelin on the heart is the most controversial topic. On the one hand, in experiments on animals, it protected the myocardium during ischemia, and in humans, with a single injection, it increased the ejection fraction. On the other hand, no one has tested how the heart reacts to long-term exposure to the peptide through the CD36 receptor.
Experience with other ghrelin receptor agonists adds caution. A study of ibutamoren in elderly patients after hip fracture (Adunsky et al., 2011) was stopped early, and the authors cited a congestive heart failure signal among the reasons. This result concerns a different molecule and a vulnerable group, but shows that the effect on the cardiovascular system cannot be considered a priori beneficial.
Prolonged elevations of prolactin, ACTH, and cortisol are also potential sources of problems. Chronic hyperprolactinemia is associated with suppression of sexual function and decreased bone mineral density, while chronically elevated cortisol is associated with hypertension, visceral obesity, and sleep disturbances.
- Known: acute increase of prolactin, ACTH, cortisol; tachyphylaxis with prolonged administration.
- Biologically plausible: impaired insulin sensitivity, fluid retention, effect on blood pressure.
- Unknown: cancer risk, long-term effects on the heart, immunogenicity, effects on fertility.
It is worth mentioning separately the issue of restoring own regulation. In a study by Rahim et al. (1998) response to hexarelin partially recovered after a break, which is encouraging. However, how the growth hormone axis behaves after years of intermittent stimulation is unknown.
What should be monitored and what should be avoided
The editors do not give recommendations on the use of unregistered peptides. However, people who already have such experience should know what health indicators are associated with the described risks, so that they can be discussed with the doctor openly and without judgment.
The basic list that can be prescribed by a doctor usually includes fasting glucose and glycated hemoglobin, IGF-1, prolactin, lipid profile, blood pressure, as indicated — ECG and echocardiography. These indicators should be interpreted by a specialist, taking into account age and concomitant conditions.
It is important not to hide the fact of using peptides from the doctor. Openness allows you to correctly explain changes in analyzes and identify problems in time. The doctor is obliged to maintain confidentiality, and his goal is to help, not to punish.
Finally, the most effective way to reduce long-term risks is to avoid exposure without medical indications. There are safe and proven factors to maintain a healthy growth hormone axis: adequate sleep, regular exercise, weight control, and a balanced diet.
Editorial conclusions
The long-term safety of hexarelin has not been studied: the longest studies in humans lasted several months and primarily evaluated hormonal response.
Indirect evidence points to several plausible risk areas: impairment of glucose metabolism, potential association of elevated IGF-1 with cancer risk, chronic effects on prolactin and cortisol, and unexplored effects on the heart.
Experience with another ghrelin receptor agonist, ibutamoren, suggests that even in randomized trials, such substances have shown undesirable metabolic effects.
We recommend that you also read our materials on the side effects of hexarelin, its mechanism of action in simple words and the status of the peptide on the WADA list and legislation.
List of used literature
- Rahim A, O'Neill PA, Shalet SM. Growth hormone status during long-term hexarelin therapy. J Clin Endocrinol Metab. 1998;83(5):1644â1649.
- Nass R, Pezzoli SS, Oliveri MC, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med. 2008;149(9):601â611.
- Renehan AG, Zwahlen M, Minder C, et al. Insulin-like growth factor (IGF)-I, IGF binding protein-3, and cancer risk: systematic review and meta-regression analysis. Lancet. 2004;363(9418):1346â1353.
- Melmed S. Acromegaly pathogenesis and treatment. J Clin Invest. 2009;119(11):3189â3202.
- Adunsky A, Chandler J, Heyden N, et al. MK-0677 (ibutamoren mesylate) for the treatment of patients recovering from hip fracture: a multicenter, randomized, placebo-controlled phase IIb study. Arch Gerontol Geriatr. 2011.
- Mao Y, Tokudome T, Kishimoto I. The cardiovascular action of hexarelin. J Geriatr Cardiol. 2014;11(3):253â258.
- Holt RIG, Ho KKY. The use and abuse of growth hormone in sports. Endocr Rev. 2019;40(4):1163â1185.
