Lab Reference Library / Adipsin (Complement Factor D)
Metabolic & Hormonal
Adipsin (Complement Factor D)
Adipsin · Complement Factor D · CFDReference range, optimal functional medicine levels, and why adipsin is an adipokine and complement pathway protease that links adipose tissue immune function to insulin secretion, metabolic syndrome, and beta-cell preservation, and why it is emerging as a sensitive early marker of metabolic and pancreatic dysfunction.
Metabolic MarkerAdipokine
Standard RangeVariable by lab
Low RiskHigher levels protective
Beta-Cell LinkYes
Unitsmcg/mL
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Category: Metabolic & Hormonal | Also known as: Complement Factor D, CFD, Factor D
1. What This Test Measures
Adipsin (complement factor D) is a serine protease produced primarily by adipocytes that serves as the rate-limiting enzyme of the alternative complement pathway. It is classified as an adipokine, joining leptin, adiponectin, and resistin as a fat-derived hormone with systemic metabolic effects. Research has established that adipsin directly stimulates pancreatic beta-cell insulin secretion through complement C3a receptor-mediated signaling on beta cells, links adipose tissue immune function to systemic complement activation, and serves as a sensitive marker of both adipose tissue metabolic health and residual beta-cell function.
Unlike most complement proteins produced by the liver, adipsin is produced predominantly by white adipose tissue, making its circulating levels a reflection of adipose tissue secretory function. Its dual role as complement pathway protease and insulin secretagogue represents a newly recognized adipose-pancreas-immune axis with significant implications for metabolic disease understanding.
2. Clinical Significance
Low Adipsin (Impaired Function)
- Associated with reduced beta-cell insulin secretion capacity: adipsin stimulates beta cells through C3a; low adipsin removes this stimulatory signal
- Predicts earlier progression from prediabetes to type 2 diabetes in multiple longitudinal studies
- Marker of adipose tissue dysfunction and reduced adipokine secretory capacity
- Associated with low adiponectin and high leptin resistance patterns
- Joslin Diabetes Center research identified declining adipsin as an early predictor of beta-cell failure before clinical disease manifestation
High Adipsin (Overactivation)
- Elevated in obesity reflects adipose tissue overproduction of complement factor D and alternative pathway overactivation
- Drives systemic complement-mediated inflammation contributing to insulin resistance and endothelial dysfunction
- Associated with elevated hs-CRP, elevated leptin, and low adiponectin in the metabolic syndrome pattern
- High adipsin with obesity and metabolic syndrome context differs from high adipsin in lean individuals, where it may represent adequate adipokine production
- Complement C3 cleavage products from adipsin activity promote adipocyte lipid storage (lipogenesis), contributing to adipose expansion
3. Adipsin as an Emerging Metabolic Marker
Adipsin testing is most informative when interpreted alongside the complete adipokine and metabolic panel: adiponectin (high is protective), leptin (high with obesity signals resistance), fasting insulin, C-peptide, and HOMA-IR. Together these markers provide a comprehensive picture of adipose tissue endocrine function and beta-cell reserve that standard glucose and HbA1c panels cannot capture. Adipsin specifically adds information about residual beta-cell stimulation capacity and adipose immune pathway activation.
4. Related Lab Tests
C-PeptideBeta-Cell Function Companion Marker
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Fasting InsulinInsulin Resistance and Beta-Cell Context
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LeptinAdipokine Panel Companion
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AdiponectinHigh-Molecular-Weight Adipokine Companion
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HbA1cGlycemic Context for Adipsin Interpretation
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hs-CRPComplement Pathway Inflammation Context
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5. Clinical Perspective
Clinical Perspective
Adipsin is one of the newer markers I have added to my comprehensive metabolic panels because it gives me a window into something that neither fasting insulin nor HbA1c can show: the state of the adipose-pancreas signaling axis. When a patient's adipsin is trending low alongside declining C-peptide and rising HbA1c, I am watching beta-cell reserve erode in real time. That trajectory changes everything about how urgently I prioritize metabolic intervention. Adipsin and the complete adipokine panel, alongside the conventional metabolic markers, give me a far more complete biological picture of where a patient is in the metabolic disease spectrum and how much beta-cell function remains to be preserved.
Brian Lamkin, DO | Founder, The Lamkin Clinic | Edmond, Oklahoma
6. Frequently Asked Questions
What is adipsin and why is it measured?
Adipsin (complement factor D) is produced by fat cells and serves two functions: it activates the alternative complement immune pathway, and it directly stimulates pancreatic beta-cell insulin secretion through C3a signaling. Low adipsin is associated with beta-cell dysfunction and earlier progression to type 2 diabetes; high adipsin in obesity reflects adipose tissue complement overactivation and systemic inflammation.
What does low adipsin indicate?
Low adipsin suggests impaired adipose tissue endocrine function and is associated with reduced beta-cell insulin secretion capacity and accelerated progression from prediabetes to type 2 diabetes. Research demonstrates that adipsin declines before clinical beta-cell failure becomes apparent on standard glucose testing, making it a potentially useful early marker of pancreatic reserve in metabolically at-risk individuals.
Is adipsin testing widely available?
Adipsin testing is available through specialized functional medicine laboratories as part of comprehensive adipokine panels. Reference ranges vary by assay platform and are less standardized than conventional metabolic markers. Clinical interpretation requires context from the complete metabolic and adipokine panel including adiponectin, leptin, C-peptide, fasting insulin, and HOMA-IR.
Content authored and clinically reviewed by Brian Lamkin, DO, founder of The Lamkin Clinic in Edmond, Oklahoma. Brian Lamkin, DO has 25+ years of experience in functional and regenerative medicine. This page reflects current functional medicine practice standards and is updated as new clinical evidence becomes available.
Adipsin connects adipose tissue immune function to beta-cell insulin secretion, revealing a metabolic axis that standard glucose panels cannot measure.
The complete adipokine panel provides a biological picture of metabolic disease trajectory that conventional labs miss. Schedule a consultation for a comprehensive metabolic and adipokine assessment.
Schedule a ConsultationMedical Disclaimer: This content is provided for educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Lab interpretation should always be performed in clinical context by a qualified healthcare provider. Reference ranges and optimal targets may vary based on individual patient history, clinical presentation, and laboratory methodology. Schedule a consultation to discuss your specific results with Dr. Lamkin.