What is Triiodothyronine Uptake?
Most circulating thyroid hormone is attached or “bound” to carrier proteins like thyroid-binding globulin (TBG) in the blood.
T3 uptake levels are particularly important to check for women because estrogen increases TBG levels. When TBG rises, total T4 and total T3 can increase on lab results even though free (active) hormone levels remain normal. This can make thyroid results appear abnormal despite stable thyroid function.
- If binding proteins are elevated, T3 uptake appears lower.
- If binding proteins are reduced, T3 uptake appears higher.
Why Does T3 Uptake Matter?
T3 uptake improves the accuracy of thyroid interpretation and diagnosis for women. It helps:
- Provide context for Total T4 results by reflecting changes in thyroid-binding protein levels that can falsely raise or lower total hormone measurements
- Identify protein-related shifts caused by pregnancy, estrogen therapy, or liver conditions
- Distinguish true thyroid dysfunction from changes in carrier protein levels by reflecting shifts in TBG.
- Improve estimation of active thyroid hormone by contributing to the calculation of the Free Thyroxine Index (FTI)
Book your test now
Test 40+ biomarkers & meet with a longevity physician, uncover the root cause of symptoms
- HSA/FSA eligible
- Physician reviewed
- 100% satisfaction guaranteed
How to Interpret T3 Uptake?
Without T3 uptake, Total T4 can sometimes appear falsely high or falsely low.
(Ranges may vary slightly by lab)
Standard reference ranges represent the middle 95% of healthy individuals but don’t necessarily reflect levels associated with longevity. Optimal ranges are derived from clinical guidelines, peer-reviewed research, and real-world outcomes data, with an emphasis on levels associated with peak functioning and reduced disease risk.
Benefits of Optimizing T3
- Improved accuracy of thyroid hormone interpretation
- Better clarity around metabolic symptoms
- More precise evaluation of estrogen-related thyroid shifts
- Reduced risk of misdiagnosis
Know your numbers. Own your health.
40+ biomarkers that reflect how your body is functioning — and where there’s room to optimize. Plus a clinical consult and personalized treatment plan. All for $65.
Low T3 Uptake Levels
Low T3 uptake typically reflects increased thyroid-binding globulin (TBG) levels. Low uptake does not automatically mean hypothyroidism in women. It often reflects altered protein binding rather than reduced thyroid hormone production.
Symptoms:
- Fatigue
- Unexplained weight gain
- Cold sensitivity
- Brain fog
- Dry skin
Causes:
- Pregnancy
- Oral contraceptives or estrogen therapy
- Liver disease
- Genetic increases in thyroid-binding globulin
- Hypothyroidism
Healthspan Impacts:
- Slower metabolism
- Elevated cholesterol levels1
- Reduced cognitive function2
- Increased risk of arrhythmias
- Increased fatigue and reduced quality of life
High T3 Uptake Levels
High T3 uptake typically reflects reduced thyroid-binding globulin (TBG) levels. High uptake does not automatically mean hyperthyroidism. It may simply indicate fewer available binding proteins.
Symptoms:
- Anxiety or feeling “wired”
- Heat intolerance
- Unintentional weight loss
- Rapid heartbeat
- Irritability
- Sleep disruption
Causes:
- Hyperthyroidism
- Graves’ disease
- Protein deficiency
- Liver dysfunction
- Androgen therapy
Healthspan Impacts:
- Increased cardiovascular strain and risk of arrhythmias3,4
- Higher risk of bone density loss and osteoporosis
- More sleep disturbances5
- Accelerated metabolic stress
How Hone Treats Out-of-Range T3 Uptake
Hone physicians evaluate T3 uptake levels for our female patients alongside TSH, free T4, free T3, and thyroid antibodies as part of a comprehensive blood panel. Based on these test results, symptoms, and overall health, they create a personalized treatment plan that may include medications, supplements, and lifestyle changes.
Liu H & Peng D. (2002). Update on dyslipidemia in hypothyroidism: the mechanism of dyslipidemia in hypothyroidism. Endocr Connect.
↑Ye, Y., et al. (2022). Association of Hypothyroidism and the Risk of Cognitive Dysfunction: A Meta-Analysis. Journal of Clinical Medicine.
↑Singh, H., et al. (2024). Subclinical thyroid dysfunction and the risk of incident atrial fibrillation: A systematic review and meta-analysis. PLOS ONE.
↑Feldt-Rasmussen U & Klose M (202). Clinical Strategies in the Testing of Thyroid Function. National Library of Medicine.
↑Green, M. E., Bernet, V., & Cheung, J. (2021). Thyroid Dysfunction and Sleep Disorders. Frontiers in Endocrinology.
↑Larsen, C. B., et al. (2024). Selenium supplementation and placebo are equally effective in improving quality of life in patients with hypothyroidism. European Thyroid Journal.
↑Severo JS, et al (2019). The Role of Zinc in Thyroid Hormones Metabolism. Int J Vitam Nutr Res.
↑Pałkowska-Goździk, E., Lachowicz, K., & Rosołowska-Huszcz, D. (2017). Effects of Dietary Protein on Thyroid Axis Activity. Nutrients
↑
Reviewed for Accuracy by Our Medical Review Board
This biomarker information has been reviewed by a member of Hone’s medical review board. As part of the medical review team, physicians fact-check this content against the latest research and their own experience treating their patients.
Ashley Winter, M.D., is a board-certified urogynecologist trained at Weill Cornell and Cleveland Clinic. She specializes in female and male sexual dysfunction, urinary issues, genital pain, and hormone therapy.
James Staheli, D.O., is the Medical Director for Broad Health, Hone Health’s affiliated medical practice and a family medicine doctor in Atlanta, Georgia.
