IGF-1 Side Effects: What Studies Report

Why IGF-1 safety appears in several different literatures

Insulin-like growth factor 1 (IGF-1) is a hormone produced largely in the liver in response to growth hormone (GH) signalling and carried in blood bound to binding proteins. Because it sits on the same endocrine axis as growth hormone and overlaps functionally with insulin signalling, safety information about IGF-1 does not come from one tidy body of trials. It is scattered across endocrinology, sports medicine, ophthalmology, oncology-adjacent receptor research and animal physiology. A 2018 review of hormones in muscle hypertrophy described IGF-1 among the anabolic hormones studied in relation to skeletal muscle adaptation and cautioned that the hormonal story is more complex than single-hormone models suggest (PMID 29172848). That complexity matters for safety, because a signal that drives tissue growth in one context is also implicated in metabolic and cardiovascular regulation in another.

This page is for educational purposes only and is not medical advice; consult a licensed physician about any hormone, medication or health decision. Nothing here describes a protocol, and no dose is presented as appropriate for any person.

Where the safety evidence comes from

Cardiovascular Findings: What Studies Report

The most consistently discussed safety theme in the IGF-1 literature is cardiovascular. A 2019 review in Growth Hormone & IGF Research examined the relationship between IGF-1 and cardiovascular disease, and the authors discussed evidence that deviations from mid-range IGF-1 — both lower and higher circulating concentrations — have been associated with cardiovascular outcomes rather than a simple linear "more is better" pattern (PMID 30735831). Researchers in that review framed IGF-1 as both a possible mediator and a possible marker, which is an important distinction: an association between a hormone level and an outcome does not establish that changing the hormone changes the outcome.

Sports-endocrinology reviews have approached the same tissue from the misuse angle. The 2023 review of doping with growth hormone, IGF-1, insulin and erythropoietin described the endocrine and systemic consequences that clinicians have associated with non-medical use of these agents in athletes, and noted the detection and regulatory context in which they are banned (PMID 36736729). That review is one of the few sources that addresses IGF-1 specifically as something used outside clinical supervision.

Why heart and vessel tissue is a plausible target

IGF-1 receptors are expressed widely, including in cardiac and vascular tissue, which is part of why the 2019 cardiovascular review treated the IGF-1 axis as physiologically relevant to the heart rather than an incidental laboratory value (PMID 30735831). The review did not present an interventional safety profile for administered IGF-1 in healthy adults, and no verified paper summarised here does.

Metabolic and Glucose-Related Signals: What Studies Report

IGF-1 shares structural and signalling overlap with insulin, and the sports-endocrinology literature treats that overlap as central to risk. The 2023 doping review grouped growth hormone, IGF-1 and insulin together precisely because their misuse in sport raises overlapping metabolic concerns, and the authors discussed the endocrine hazards attached to that class of agents (PMID 36736729). The 2018 hypertrophy review likewise placed IGF-1 within an interacting hormonal network rather than treating it as an isolated growth switch (PMID 29172848).

Chronic GH and IGF-1 excess is also studied as a disease state. Reviews of pregnancy in acromegaly — a condition defined by GH and IGF-1 excess — described the clinical monitoring, comorbidity assessment and treatment decisions that clinicians reported managing in these patients, including the interpretation of GH and IGF-1 measurements during pregnancy (PMID 26623004). A second review of pregnancy and acromegaly covered maternal and fetal considerations and the follow-up that specialists reported using in this population (PMID 27568329). Disease-state literature is not a model of short-term administration, but it is the main human window into what sustained elevation of the axis looks like clinically.

IGF-1 Receptor Blockade: What Studies Report

A useful mirror image comes from drugs that block, rather than supply, IGF-1 signalling. The THRIVE trial was a phase 3, randomised, double-masked, placebo-controlled study of veligrotug, an IGF-1 receptor–directed antibody, in active thyroid eye disease, and researchers reported both efficacy endpoints and treatment-emergent adverse events in that design (PMID 42223386). Separately, a 2026 report in Orbit described menstrual changes associated with teprotumumab, another IGF-1 receptor–blocking antibody, in patients treated for thyroid eye disease (PMID 41528831).

Two things follow from that literature. First, IGF-1 receptor signalling is not confined to muscle or bone; the reported menstrual changes with teprotumumab indicate reproductive-axis involvement (PMID 41528831). Second, systemic modulation of this pathway in either direction has measurable off-target consequences, which is why receptor-blocking agents are studied in controlled trials with formal safety reporting (PMID 42223386).

Animal and Preclinical Findings: What Studies Report

Animal work is where the growth-axis mechanism is most directly manipulated. A 2023 Science study reported that microbe-mediated intestinal NOD2 stimulation improved linear growth in undernourished infant mice, linking gut signals to the somatotropic growth axis in a controlled animal model (PMID 36821686). Findings of that kind describe mechanism in juvenile, undernourished animals; researchers did not present them as evidence for hormone administration in adults.

On the human physiology side, a 2020 review in Redox Biology examined physical activity and exercise as strategies to manage frailty and discussed the biological pathways that exercise engages in ageing populations (PMID 32234291). That review is relevant context because much of the interest in the GH/IGF-1 axis concerns muscle preservation, and the review's focus was on exercise rather than hormonal intervention (PMID 32234291).

Product Quality, Immunogenicity and Unregulated Material: What Studies Report

Safety discussion in the peptide and growth-axis literature is not only about pharmacology; it is also about what is in the vial. A review of biosimilar growth hormone discussed comparability exercises, immunogenicity assessment and the regulatory expectations applied to growth-axis biologics, noting that apparently similar products are not automatically interchangeable (PMID 22108957). A 2026 review of therapeutic peptides in orthopaedics described the applications, challenges and evidence gaps in this field, including the regulatory and quality questions that surround peptide products used outside approved indications (PMID 41490200).

Regulatory framing, stated as fact rather than advice: recombinant IGF-1 exists as a prescription pharmaceutical in some jurisdictions and is dispensed under physician supervision, while peptide material sold with "research use only" labelling is not authorised for human administration and is not manufactured to pharmaceutical standards. IGF-1 is also on prohibited-substance lists in sport, a point the 2023 doping review addressed alongside detection methods (PMID 36736729).

What the literature does not establish

• No dose-response safety profile for healthy adults. None of the verified papers summarised here reported an administered IGF-1 dose range in healthy people, so no such figures appear on this page.
• Association is not causation. The 2019 cardiovascular review discussed IGF-1 concentrations as associated with outcomes, and researchers were explicit that mechanistic and marker interpretations both remain in play (PMID 30735831).
• Receptor-blockade adverse events are not a reverse map. Menstrual changes reported with an IGF-1 receptor–blocking antibody describe that drug in that patient population (PMID 41528831); they do not predict what supplying IGF-1 would do.
• Animal results are animal results. The growth-axis improvement reported in undernourished infant mice was observed in that model (PMID 36821686).
• Evidence gaps are acknowledged in the field. The 2026 orthopaedic peptide review listed challenges and future directions rather than settled safety conclusions (PMID 41490200).

How researchers frame monitoring in published work

Across these papers, the monitoring themes that recur are metabolic (glucose handling, given the insulin overlap discussed in the doping review), cardiovascular (given the associations reviewed in 2019), and structural or endocrine follow-up in states of chronic axis elevation such as acromegaly (PMID 36736729, PMID 30735831, PMID 27568329). In trial settings, safety is captured through predefined adverse-event reporting in blinded, placebo-controlled designs, as in the phase 3 IGF-1 receptor antibody study (PMID 42223386). Case reports and post-marketing series then add signals that trials were too small or too short to detect, as with the reported menstrual changes on teprotumumab (PMID 41528831).

For readers wanting the underlying biology — what IGF-1 is, how the GH/IGF-1 axis is regulated, and how binding proteins change interpretation of a blood level — that material is covered in PeptideU's IGF-1 course rather than repeated here; this page stays on the safety and adverse-event literature.

References

• IGF-1 and cardiovascular disease (Growth Hormone & IGF Research, 2019)
• Doping and sports endocrinology: growth hormone, IGF-1, insulin, and erythropoietin (Revista Clinica Espanola, 2023)
• The role of hormones in muscle hypertrophy (The Physician and Sportsmedicine, 2018)
• Pregnancy in acromegaly (Therapeutic Advances in Endocrinology and Metabolism, 2015)
• Pregnancy and acromegaly (Pituitary, 2017)
• THRIVE: A Phase 3, Randomized, Double-Masked, Placebo-Controlled Study of Veligrotug for Active Thyroid Eye Disease (Ophthalmology, 2026)
• Teprotumumab associated menstrual changes (Orbit, 2026)
• Biosimilar growth hormone (Indian Journal of Pediatrics, 2012)
• Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions (JAAOS Global Research & Reviews, 2026)
• Microbe-mediated intestinal NOD2 stimulation improves linear growth of undernourished infant mice (Science, 2023)
• Physical activity and exercise: Strategies to manage frailty (Redox Biology, 2020)