The Athlete Biological Passport for Peptide Detection
WADA and Peptide Doping
99% specificity
The ABP's endocrine module flagged 20 of 27 growth hormone users at 99% specificity, including 17 who had already stopped treatment.
Holt et al., Journal of Clinical Endocrinology & Metabolism, 2021
Holt et al., Journal of Clinical Endocrinology & Metabolism, 2021
View as imageGrowth hormone releasing peptides like GHRP-2, GHRP-6, and ipamorelin are nearly identical to molecules your body already produces. They clear the bloodstream in hours. Traditional drug testing, built to find foreign chemicals in a single urine sample, was never designed to catch them. That gap is why WADA bans peptides and why the Athlete Biological Passport exists: instead of searching for the drug itself, it watches what the drug does to the body over time.
The Athlete Biological Passport (ABP) is WADA's longitudinal monitoring program that builds an individual biomarker profile for each athlete. When a peptide like a growth hormone secretagogue pushes IGF-1 or other markers outside that athlete's personal range, the passport flags it. The approach does not depend on catching the substance in a sample. It catches the biological fingerprint the substance leaves behind.
Key Takeaways
- The ABP's endocrine module, launched in 2023, tracks IGF-1 and P-III-NP to detect growth hormone peptide abuse at 99% specificity (Holt et al., J Clin Endocrinol Metab, 2021)
- At that specificity level, the endocrine module flagged 74% of growth hormone users, including 63% who had already stopped treatment
- Bayesian statistical models build individual reference ranges for each athlete, making population-level masking strategies ineffective
- Growth hormone releasing peptides like GHRP-2 and GHRP-6 have half-lives under 60 minutes, making direct detection windows extremely narrow[1]
- Dried blood spot technology may enable remote self-sampling, allowing longitudinal monitoring between formal tests[2]
- Novel glycine-modified peptide analogs found in seized doping materials are designed to evade both direct tests and established biomarker panels[3]
What Is the Athlete Biological Passport?
The ABP is an individual electronic record that collects biological variables from each athlete over months or years. WADA introduced it in 2008 and made it operational in 2009. Rather than testing whether a specific banned substance is present in a single sample, the ABP uses repeated measurements to build a statistical profile of what is normal for that specific person.
The system relies on Bayesian inference. Each new sample updates the athlete's expected range. The first few samples establish a baseline. Every subsequent sample either confirms that baseline or triggers a flag. The mathematical model sets individual upper and lower limits that narrow over time as more data accumulates. A deviation that would be normal for the general population might be highly abnormal for a specific athlete whose values have been stable across 15 previous samples.
When a value falls outside the expected range, the system generates a sequence of atypical passport findings (ATPFs). These go to a panel of three independent experts: typically an endocrinologist, a hematologist, and a laboratory scientist. The panel reviews the profile, considers confounders like altitude training or illness, and determines whether the abnormality is consistent with doping.
Why Peptide Doping Is Hard to Detect Directly
Peptide hormones create a specific problem for anti-doping laboratories. Many banned peptides are structurally identical or nearly identical to endogenous molecules. Growth hormone releasing peptides stimulate the pituitary to produce more of the athlete's own growth hormone. The GH that enters the bloodstream is genuine, endogenous GH. No amount of mass spectrometry testing can distinguish it from GH produced during normal sleep or exercise.
The peptides themselves are detectable, but the window is narrow. Barroso et al. (2012) documented that peptide hormones pose persistent analytical challenges for WADA-accredited laboratories because of their low circulating concentrations, rapid clearance, and structural similarity to endogenous molecules.[4] Thomas et al. (2011) showed that GHRP-2, GHRP-6, and their metabolites could be detected in urine, but only within hours of administration.[5]
This is where the ABP fills the gap. An athlete using GHRPs several times per week may have a vanishingly small window where the peptide itself is detectable in any single test. But the downstream effects on IGF-1, P-III-NP, and other biomarkers persist for days or weeks. The ABP catches the footprint, not the footstep.
The Three Modules of the ABP
Haematological module (2009)
The first module tracks blood variables that indicate manipulation of oxygen-carrying capacity: hemoglobin, hematocrit, reticulocyte percentage, and the OFF-score (a ratio of hemoglobin to reticulocyte percentage). It was built to catch EPO doping and blood transfusions. The haematological module has generated hundreds of anti-doping rule violations since its launch and has been upheld repeatedly by the Court of Arbitration for Sport (CAS).
Steroidal module (2014)
The second module monitors urinary steroid ratios, particularly the testosterone-to-epitestosterone (T/E) ratio and related metabolites. Individual longitudinal profiling replaced the old population-based 4:1 T/E threshold, which missed athletes with naturally low ratios who were doping and falsely flagged athletes with naturally elevated ratios.
Endocrine module (2023)
The third and newest module targets growth hormone doping, including peptide-based approaches. WADA formally introduced it in August 2023, ahead of the Paris 2024 Olympics. The International Testing Agency (ITA) spearheaded its implementation in collaboration with the Paris WADA-accredited laboratory.
This module is the one most directly relevant to peptide doping detection, and it represents the culmination of over a decade of development work on growth hormone biomarkers. Thevis et al. (2011) had already demonstrated that LC-MS methods could detect selected peptide hormones in anti-doping samples, but the ABP approach goes beyond direct detection by tracking downstream biomarker changes.[6]
How the Endocrine Module Catches Growth Hormone Peptide Users
The endocrine module tracks two primary biomarkers: insulin-like growth factor 1 (IGF-1) and the N-terminal propeptide of type III procollagen (P-III-NP). Both rise when growth hormone levels increase, whether from exogenous GH injection or from peptide secretagogues that stimulate endogenous GH release.
These two markers are combined into a composite score called the GH-2000 score, adjusted for age and sex. The name comes from the GH-2000 project, a European research initiative that validated these biomarkers for anti-doping use in the early 2000s.
Holt et al. published the key validation data in the Journal of Clinical Endocrinology & Metabolism (2021). At 99% specificity (meaning only a 1% false positive rate), the ABP-based approach flagged 20 of 27 individuals receiving growth hormone treatment. That is a 74% sensitivity rate. Among those 27 subjects, 17 were detected even after they had stopped GH treatment, a 63% post-cessation detection rate.
Sensitivity varied with dose and duration. After 7 days of treatment, sensitivity ranged from 12.5% to 71.4% depending on the GH concentration. After 21 days, it peaked at 57.1% to 100%. One week after cessation of treatment, sensitivity remained between 37.5% and 71.4% for the low and high dose groups respectively.
These numbers represent a major advance over the previous population-based hGH Biomarkers Test, which required a single sample to exceed a fixed threshold. The ABP approach can flag smaller deviations because it compares each athlete to their own baseline, not to the general population.
For peptide secretagogues specifically, the detection window is wider through the ABP than through direct testing. Thevis et al. (2014) noted that while the peptides themselves clear rapidly, the biomarker perturbations they cause persist long enough to be captured in longitudinal monitoring.[7]
Dried Blood Spots: The Next Evolution in Longitudinal Monitoring
A major limitation of the current ABP is sample collection logistics. Athletes must report their whereabouts and be available for out-of-competition testing, but visits are expensive and infrequent. An athlete might be tested 6 to 12 times per year. A peptide user who times their cycles around the testing windows can potentially evade detection.
Dried blood spot (DBS) technology could change this. WADA acknowledged DBS samples for routine doping control purposes, and researchers have proposed using DBS for remotely supervised self-sampling.[2]
Lange et al. (2020) developed a fully automated DBS sample preparation method that detected lower molecular mass peptide and non-peptide doping agents using LC-HRMS. The robotic-assisted system measured hematocrit from the dried spot via near-infrared spectroscopy before automated extraction.[8]
Brockbals et al. (2024) advanced this further by developing LC-MS/MS-based peptide analysis for DBS that could estimate when the blood sample was collected, addressing a key chain-of-custody concern with self-sampling. If an athlete provides weekly DBS samples from home, the temporal data creates a much denser longitudinal profile than quarterly in-person testing.[2]
For peptide detection specifically, Gorgens et al. (2018) showed that improvements in LC-MS sample preparation and mass spectrometric detection had already expanded the number of peptidic drugs detectable in initial testing procedures, covering GHRPs, GnRH analogs, and other sub-2-kDa peptides.[9] Combined with DBS-based longitudinal biomarker tracking, the net tightens considerably.
Legal Challenges and the Burden of Proof
The ABP's reliance on statistical inference rather than direct substance identification has created legal complications. Anti-doping rule violations based on passport abnormalities are prosecuted under WADA Code Article 2.2 (use of a prohibited substance or method), and the burden of proof requires "comfortable satisfaction" of the hearing panel, a standard between balance of probabilities and beyond reasonable doubt.
Several athletes have challenged ABP findings at the Court of Arbitration for Sport. CAS has generally upheld ABP-based sanctions when the expert panel process was properly followed, but has overturned cases where procedural irregularities existed or where medical explanations were not adequately considered.
Cost is a barrier to defense. The CAS appeal process is expensive, and not all athletes can afford it. French cyclist Franck Bonnamour retired under an ABP-based violation while maintaining his innocence, stating publicly that the cost of a legal defense was prohibitive. Tennis player Simona Halep successfully appealed a four-year ban to CAS in 2024, having it reduced to nine months, but her case involved both an ABP abnormality and a direct positive test for Roxadustat.
Beumer et al. (2025) published data on biological variation of cardiac biomarkers in athletes across an entire sport season, demonstrating that even well-validated biomarkers show meaningful within-individual variation that must be accounted for in longitudinal monitoring programs.[10] This kind of variation data is what defense attorneys scrutinize when challenging ABP findings.
What the ABP Cannot Catch
The endocrine module was designed around known GH and IGF-1 physiology. Athletes and suppliers adapt.
Gajda et al. (2019) analyzed pharmaceutical preparations seized by Danish customs and identified glycine-modified analogs of GHRP-2, GHRP-6, and ipamorelin. These designer peptide variants are structurally distinct enough to evade direct detection assays calibrated for the parent compounds. Whether they produce the same biomarker perturbations detectable by the ABP's endocrine module is unknown.[3]
Gomez-Guerrero et al. (2022) reviewed the broader challenge: peptides appear on WADA prohibited list sections S2, S4, and S5, and many have very short half-lives that make direct detection extremely difficult. Synthetic reference standards are essential for laboratories but are not always available for novel analogs entering the black market.[11]
The emerging threats landscape includes novel peptide sequences that may not trigger established biomarker pathways. A secretagogue that stimulates GH release through a pathway that does not proportionally elevate IGF-1 or P-III-NP could theoretically evade the endocrine module entirely.
Oral secretagogues like MK-677 (ibutamoren) present additional detection challenges. Philip et al. (2022) characterized MK-677 and its metabolites for doping control in thoroughbred horses, but the small molecule's pharmacokinetics differ substantially from injectable peptides, and its biomarker signature in the ABP context remains under study.[12]
Thomas et al. (2021) demonstrated that ghrelin and desacyl ghrelin could be measured in human plasma and urine for doping controls. Ghrelin, classified as a prohibited substance by WADA due to its growth hormone releasing properties, could be quantified at meaningful levels. Distinguishing exogenous ghrelin administration from endogenous fluctuations driven by fasting, exercise, or circadian rhythm remains a challenge that longitudinal monitoring only partially resolves.[13]
Where This Is Heading
The ABP will likely expand. Judak et al. (2021) documented a decade of progress in small peptide doping control analysis, noting that LC-MS methodologies had matured substantially but that the field continues to evolve with new analytes and new evasion strategies.[1] Integration of direct detection data with ABP longitudinal profiles, combined with more frequent sampling via DBS, creates a multilayered system that is progressively harder to beat.
The fundamental physics of the ABP cannot be evaded by any single strategy. An athlete can cycle off before a test, use a novel analog, or micro-dose below direct detection thresholds. But if the peptide does what the athlete wants it to do (raise GH, build muscle, improve recovery), it will leave biomarker traces. The ABP is designed to find those traces in the patterns that accumulate over time.
The Bottom Line
The Athlete Biological Passport represents a fundamental shift in anti-doping strategy for peptide detection. Instead of trying to find substances that clear the body in hours, the ABP tracks what those substances do to an athlete's biomarker profile over months and years. The endocrine module, launched in 2023, has demonstrated strong performance against growth hormone doping at clinically relevant specificity levels. Gaps remain, particularly around novel peptide analogs and the cost of athlete defense, but the direction is clear: longitudinal monitoring is replacing single-sample testing as the primary tool for catching peptide doping.