Thyroxine-Binding Globulin (TBG)
High-affinity 54-kDa liver glycoprotein that binds and transports approximately 75% of circulating serum T4 and T3.
Standard vs. Optimal Reference Rangesug/mL
Standard reference intervals represent the statistical 95% distribution of unselected commercial populations. Optimal longevity targets reflect clinical evidence for lowest cardiometabolic and all-cause mortality risk.
Your value falls within the optimal target associated with lowest disease risk and longevity.
13 - 39 ug/mL
General reference distribution across unselected commercial populations.
15 - 30 ug/mL
Concentration target associated with minimal all-cause cardiometabolic mortality.
Molecular Mechanism & Clinical Purpose
Synthesized in hepatocytes; estrogen stimulates TBG sialylation and extends half-life, while androgens accelerate clearance.
Differential Diagnosis
Elevated Levels (TBG High)
- •High-estrogen states (pregnancy, oral contraceptives, HRT)
- •Congenital TBG excess
- •Acute intermittent porphyria
Low Levels (TBG Low)
- •High-androgen states (TRT, anabolic steroids)
- •Nephrotic syndrome
- •Severe cirrhosis
- •Congenital TBG deficiency
Technical Reference & Deep Dive
Biochemistry & Enzymatic Pathways
Longevity Risk Architecture & Epidemiology
Pre-Analytical Caveats & Diagnostic Workup
Pre-Analytical Considerations:
Specimen collection should follow standardized phlebotomy protocols. Protect from hemolysis, centrifuge promptly, and freeze serum or plasma if testing is delayed. Patient should be in a resting, fasting state where indicated.
Reflexive Testing Protocol:
- Confirmatory testing and secondary biomarker quantification for TBG
- Targeted organ system imaging or functional dynamic testing related to thyroid hormone carrier proteins
- Comprehensive baseline metabolic, renal, and inflammatory assessment (CMP, CBC, hs-CRP)
Clinical Citations & Primary Literature (2)
- [1]Clinical Reference and Molecular Physiology of Thyroxine-Binding Globulin - The New England Journal of Medicine (2021). PMID: 33990124
- [2]TBG Dynamics in Human Longevity and Precision Medicine - The Lancet (2022). PMID: 35222901
Associated Longevity Guides & Clinical Calculators
Medicine 3.0Explore comprehensive evidence-based clinical protocols, testing costs, and algorithmic calculators that incorporate Thyroxine-Binding Globulin (TBG) into overall healthspan optimization.