Growth factors are the biological rationale underneath almost every orthobiologic, and they are also the point at which orthobiologics collide most directly with anti-doping rules. The distinction that matters is between a preparation that contains growth factors as part of an autologous product, such as platelet-rich plasma, and a purified or separately administered growth factor given as a drug, which is a different proposition both clinically and in anti-doping terms. This page also covers the blood-derived products beyond platelet-rich plasma that a sport and exercise medicine (SEM) clinician may be asked about, principally autologous conditioned serum (ACS), and it sets out how these preparations are regulated. The general orthobiologics regulatory framework is covered in the related material and is not repeated here.
What are growth factors, and which preparations contain them?
Growth factors are signalling proteins that regulate cell recruitment, proliferation, differentiation and matrix production, and the ones repeatedly named in this field are platelet-derived growth factor, transforming growth factor beta, vascular endothelial growth factor, insulin-like growth factor and fibroblast growth factor. In an autologous preparation they arrive as a mixture at whatever concentrations the patient's own tissue provides. In platelet-rich plasma they are released from platelet alpha granules once the platelets are activated. Autologous conditioned serum is produced differently: some proprietary systems incubate whole blood in treated glass-bead syringes, which stimulates leucocytes to produce anti-inflammatory mediators, most notably interleukin-1 receptor antagonist, before the serum is separated and injected, usually as a course. Protocols are not identical across products. It is best understood as a cytokine-enriched blood-derived preparation rather than a growth factor concentrate, and it is offered mainly for osteoarthritis, where the evidence is insufficient and conflicting.
Blood-derived mediator preparations differ in what they deliver: platelet-rich plasma releases growth factors from platelets, autologous conditioned serum is cytokine-enriched, and a purified or recombinant growth factor is a laboratory-produced medicinal product.
The third route is entirely different. A purified or recombinant growth factor is a laboratory-produced pharmaceutical agent given to achieve a specific biological effect, and it is not an autologous product at all. This is where the field intersects with doping, because such agents can influence tissue growth, repair and, in some cases, performance. Clinicians should also be aware of the broader use of the word biologics, which in rheumatology covers monoclonal antibodies, receptor proteins and other targeted biological agents, given systemically for inflammatory disease. These are a different class of medicine again, prescribed within specialist pathways, and the term should not be allowed to blur into the orthobiologics conversation, where it is sometimes used loosely to make an unlicensed injectable sound established.
What are the anti-doping and regulatory implications?
The anti-doping position is the most examinable content on this page and is best learned as a contrast. The World Anti-Doping Agency explicitly states that platelet-derived preparations such as platelet-rich plasma are not prohibited, and this remains the case despite their growth factor content. Specific growth factors, growth-factor modulators and substances with similar biological effects that are covered by the relevant section of the Prohibited List are prohibited at all times. That exemption for platelet-derived preparations should not be extrapolated to every autologous serum or cell product, and not every protein that is described biologically as a growth factor should be assumed prohibited without checking the list. The practical consequence is that the clinician must know exactly what is being injected: adding a growth factor or modulator that is covered by the Prohibited List, or administering one alongside, may convert a permitted procedure into an anti-doping rule violation. Autologous conditioned serum in particular should be checked specifically with the relevant anti-doping organisation, especially given recent changes concerning blood withdrawal. Athletes are sometimes offered proprietary preparations abroad with contents that are not fully disclosed, and the correct response is that a preparation whose contents cannot be established cannot be assumed to be permitted. The current list and the relevant checking tools should always be consulted rather than relying on memory, since the classification of these agents has changed over time.
Platelet-derived preparations are not prohibited, but adding a growth factor or modulator covered by the Prohibited List makes the treatment prohibited. Correct at the time of writing; always check the current list.
The regulatory position follows the same logic. Medicines classification depends on the extent of manipulation and on whether the cells or tissues are intended to perform the same essential function, and same-day autologous use does not by itself determine status. A purified or recombinant growth factor is a medicinal product subject to licensing, and a culture-expanded cell product will generally meet advanced therapy medicinal product criteria. Autologous conditioned serum occupies an intermediate position that depends on the specific processing involved and should not be assumed to be exempt. Clinically, the honest summary is that the evidence for autologous conditioned serum in osteoarthritis is insufficient and conflicting, that purified growth factors have no established role in routine musculoskeletal practice in the UK, and that the word biologic is doing a great deal of persuasive work in marketing without a corresponding weight of evidence behind it. Where a patient asks, the discussion should establish what the product actually is, its regulatory status, what evidence exists for that specific preparation in that specific condition, what it costs, and, for a competing athlete, what its anti-doping status is.
Exam Tips
•Growth factors named repeatedly in this field include platelet-derived growth factor, transforming growth factor beta, vascular endothelial growth factor, insulin-like growth factor and fibroblast growth factor.
•In platelet-rich plasma, growth factors are released from platelet alpha granules once platelets are activated, at whatever concentrations the patient's own blood provides.
•Autologous conditioned serum (ACS) is a cytokine-enriched blood-derived preparation; some proprietary systems incubate whole blood in treated glass-bead syringes to stimulate mediators including interleukin-1 receptor antagonist, and the evidence in osteoarthritis is insufficient and conflicting.
•The World Anti-Doping Agency explicitly states that platelet-derived preparations are not prohibited, while growth factors and modulators covered by the relevant section of the Prohibited List are prohibited at all times; that exemption does not extend automatically to every autologous serum or cell product.
•A preparation whose contents cannot be established cannot be assumed to be permitted, so always establish exactly what is being injected.
•In rheumatology, biologic medicines include monoclonal antibodies, receptor proteins and other targeted biological agents given systemically for inflammatory disease, which is a different class from anything in this subcategory.