Research

The Science Behind
Your Markers.

Every interpretation in MarkerX is grounded in peer-reviewed research. Here are the key studies and references behind our reference ranges and recommendations.

Hormones

JCEM
Harmonized Reference Ranges for Circulating Testosterone Levels in Men
Travison TG, Vesper HW, Orwoll E, et al. · 2017
Establishes population-based reference ranges for total testosterone across multiple large cohort studies, forming the scientific foundation for the standard male testosterone reference intervals used in clinical practice.
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Endocrine Society
Testosterone Therapy in Men with Hypogonadism: An Endocrine Society Clinical Practice Guideline
Bhasin S, Brito JP, Cunningham GR, et al. · 2018
Comprehensive clinical guideline covering testosterone deficiency diagnosis thresholds, treatment targets, health outcomes, and monitoring — the reference standard for testosterone interpretation worldwide.
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JCEM
A Critical Evaluation of Simple Methods for the Estimation of Free Testosterone in Serum
Vermeulen A, Verdonck L, Kaufman JM. · 1999
Validates the Vermeulen equation for calculating bioavailable free testosterone from total testosterone and SHBG — the method underpinning "Calculated Free Testosterone" on modern lab reports.
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JCEM
Age Trends in the Level of Serum Testosterone and Other Hormones in Middle-Aged Men
Harman SM, Metter EJ, Tobin JD, et al. · 2001
Longitudinal data showing that testosterone declines ~1% per year in men from age 30, with free testosterone declining faster due to rising SHBG — supporting age-adjusted interpretation of results.
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Vitamins

JCEM
Evaluation, Treatment, and Prevention of Vitamin D Deficiency: An Endocrine Society Clinical Practice Guideline
Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. · 2011
Defines vitamin D sufficiency (≥30 ng/mL), insufficiency (20–29 ng/mL), and deficiency (<20 ng/mL), and provides evidence-based supplementation protocols that inform the optimal ranges used in MarkerX.
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Dermato-Endocrinology
Sunlight and Vitamin D: A Global Perspective for Health
Wacker M, Holick MF. · 2013
Reviews the role of vitamin D in musculoskeletal health, immune function, and athletic performance, supporting higher optimal targets of 40–60 ng/mL for active individuals.
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NEJM
Vitamin D Deficiency
Holick MF. · 2007
Landmark review establishing the global prevalence of vitamin D deficiency and its systemic consequences including bone loss, immune dysfunction, and increased cardiovascular risk.
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Lipids

Circ Cardiovasc Qual Outcomes
A Meta-Analysis of LDL-C, Non-HDL-C, and Apolipoprotein B as Markers of Cardiovascular Risk
Sniderman AD, Williams K, Contois JH, et al. · 2011
Demonstrates that apolipoprotein B is a superior predictor of cardiovascular events compared to LDL-C and non-HDL-C, underpinning why MarkerX flags ApoB as the primary atherogenic particle marker.
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JACC
2018 AHA/ACC Guideline on the Management of Blood Cholesterol
Grundy SM, Stone NJ, Bailey AL, et al. · 2018
The current US standard for cholesterol management, defining risk categories, LDL-C treatment thresholds, and the role of coronary artery calcium scoring in borderline-risk patients.
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European Heart Journal
Low-Density Lipoproteins Cause Atherosclerotic Cardiovascular Disease: Evidence from Genetic, Epidemiologic, and Clinical Studies
Ference BA, Ginsberg HN, Graham I, et al. · 2017
EAS Consensus Panel statement establishing the causal relationship between LDL-C and atherosclerosis, supporting aggressive LDL-C lowering in high-risk individuals.
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Inflammation

NEJM
Comparison of C-Reactive Protein and LDL Cholesterol Levels in the Prediction of First Cardiovascular Events
Ridker PM, Rifai N, Rose L, Buring JE, Cook NR. · 2002
Landmark study showing hsCRP is at least as powerful as LDL-C for predicting first cardiovascular events in apparently healthy women, establishing CRP as a primary inflammatory biomarker.
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NEJM
Rosuvastatin to Prevent Vascular Events in Men and Women with Elevated C-Reactive Protein (JUPITER)
Ridker PM, Danielson E, Fonseca FA, et al. · 2008
Demonstrates that lowering hsCRP through statin therapy reduces cardiovascular events even in individuals with normal LDL-C, cementing hsCRP as an independent cardiovascular risk marker.
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Liver

British Journal of Clinical Pharmacology
Muscular Exercise Can Cause Highly Pathological Liver Function Tests in Healthy Men
Pettersson J, Hindorf U, Persson P, et al. · 2008
Shows that intense resistance training can raise ALT, AST, and GGT into the "pathological" range in healthy athletes — establishing that elevated liver enzymes after exercise likely reflect muscle rather than liver damage.
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Hepatology
Nonalcoholic Fatty Liver Disease: A Systematic Review
Bellentani S, Scaglioni F, Marino M, Bedogni G. · 2010
Comprehensive review of NAFLD prevalence, risk factors, and progression, providing the clinical context for interpreting persistently elevated ALT and AST in the absence of acute exercise.
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Kidney

Annals of Internal Medicine
A New Equation to Estimate Glomerular Filtration Rate
Levey AS, Stevens LA, Schmid CH, et al. (CKD-EPI Collaboration) · 2009
Introduces the CKD-EPI equation for estimating GFR from serum creatinine — the current gold-standard formula used to calculate eGFR on lab reports and stage chronic kidney disease.
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NEJM
Chronic Kidney Disease
Levey AS, Coresh J. · 2012
Definitive review of CKD staging, progression risk factors, and the clinical significance of eGFR and albuminuria — the framework underpinning MarkerX's kidney marker interpretation.
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Blood Count

NEJM
Iron-Deficiency Anaemia
Camaschella C. · 2015
Comprehensive review of iron-deficiency aetiology, ferritin as the primary storage marker, and the distinction between iron-deficiency anaemia and anaemia of chronic disease — directly informing ferritin reference ranges in MarkerX.
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Blood
Hepcidin Regulates Cellular Iron Efflux by Binding to Ferroportin and Inducing Its Internalization
Nemeth E, Tuttle MS, Powelson J, et al. · 2004
Identifies hepcidin as the master regulator of systemic iron homeostasis, explaining why inflammation suppresses iron absorption and why ferritin can be falsely elevated during acute illness.
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Disclaimer · MarkerX references peer-reviewed research to inform its interpretations. This is not medical advice. Always consult a qualified healthcare professional before making changes to your health, medication, or supplementation.