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Journals / Journal of Health Sciences and Medicine / 2026 / Volume: 5 Issue: 2

fT3 index/TSH index ratio and free thyroid hormone index in the differential diagnosis of thyrotoxicosis

Davut Sakız(Mardin Training and Research Hospital, Department of Endocrinology and Metabolism)0000-0003-1480-888X
Murat Çalapkulu(University of Health Sciences, Diskapi Yildirim Beyazit Training and Research Hospital, Department of Endocrinology and Metabolism)0000-0002-7445-2275
Muhammed Erkam Sencar(University of Health Sciences, Diskapi Yildirim Beyazit Training and Research Hospital, Department of Endocrinology and Metabolism)0000-0001-5581-4886
Bekir Ucan(University of Health Sciences, Diskapi Yildirim Beyazit Training and Research Hospital, Department of Endocrinology and Metabolism,)0000-0002-0810-5224
İlknur Öztürk Ünsal(University of Health Sciences, Diskapi Yildirim Beyazit Training and Research Hospital, Department of Endocrinology and Metabolism)0000-0003-3999-6426
Mustafa Özbek(University of Health Sciences, Diskapi Yildirim Beyazit Training and Research Hospital, Department of Endocrinology and Metabolism)0000-0003-1125-3823
Erman Çakal(University of Health Sciences, Diskapi Yildirim Beyazit Training and Research Hospital, Department of Endocrinology and Metabolism)0000-0003-4455-7276
Pages
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Publication Date
2022-03-15
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AI Summary & Key Takeaways

AI Insight
⚡ TL;DR(Too Long; Didn't Read)

The combination of FTHI and sT3I/TSHI methods can increase diagnostic accuracy.

📌 3 Key Takeaways

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Objective & Hypothesis:Aim: Common causes of thyrotoxicosis are hyperthyroidism and destructive thyroiditis.
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Key Findings & Data:The aim of this study was to analyze whether it is possible to make a differential diagnosis for these conditions by examining free thyroid hormones, fT3/fT4 ratio, fT3 index/TSH index (fT3I/TSHI) ratio and Free Thyroid Hormone Index (FTHI).
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Conclusion & Impact:The combination of FTHI and sT3I/TSHI methods can increase diagnostic accuracy.
🔬Design:Research Article
📍Scope:Comprehensive Sample
⚙️Variables:Hyperthyroidism · Free T4 · T3/T4 ratio

Abstract

Aim: Common causes of thyrotoxicosis are hyperthyroidism and destructive thyroiditis. Hyperthyroidism is a condition characterized by high serum thyroid hormone levels as a result of over-synthesis of thyroid hormones, the most common causes of which are Graves' disease (GD) and toxic nodular goiter (TNG). Subacute thyroiditis (SAT) causes thyrotoxicosis due to the circulating thyroid hormones of destructive thyroiditis. Differential diagnosis is important because GD, TNG and SAT treatment approaches are different. The aim of this study was to analyze whether it is possible to make a differential diagnosis for these conditions by examining free thyroid hormones, fT3/fT4 ratio, fT3 index/TSH index (fT3I/TSHI) ratio and Free Thyroid Hormone Index (FTHI). Material and Method: This retrospective study included 150 patients who were diagnosed with GD, TNG and SAT. The fT3 index (fT3I) was calculated as the ratio between the fT3 value and the fT3 upper limit of normal value (fT3I=fT3/4 pg/ml). The fT4 index (fT4I) was calculated as the ratio between the fT4 value and the fT4 upper limit of normal value (fT4I=fT4/1.23 mg/dl). The TSH index (TSHI) was calculated as the ratio between TSH value and the TSH lower limit of normal limit (TSHI=TSH/0.38 mIU/L). The FTHI index was calculated using the formula of (fT3 level/fT3 upper limit of normal) / (fT4 level/fT4 upper limit of normal). Results: The fT3, fT3/fT4 ratio and FTHI were found to be higher in hyperthyroid patients compared to subacute thyroiditis patients. fT4 and fT3I/TSHI levels were similar in hyperthyroid patients and SAT patients (p=0.49, p=0.11, respectively ). The cut-off level of FTHI for hyperthyroidism was determined as 0.97 with sensitivity of 75% and specificity of 76.3% (AUC=0.833, p 324.58. Conclusion: FTHI is useful in differentiating hyperthyroid conditions such as GD and TNG from SAT. FTHI is insufficient in the differential diagnosis of Graves disease and TNG. The fT3I/TSHI ratio is higher in Graves' disease than in TNG and SAT. The combination of FTHI and sT3I/TSHI methods can increase diagnostic accuracy.

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Cite This Article

Sakız, D., Çalapkulu, M., Sencar, M. E., Ucan, B., Ünsal, İ. Ö., Özbek, M., Çakal, E. (2022). fT3 index/TSH index ratio and free thyroid hormone index in the differential diagnosis of thyrotoxicosis. Journal of Health Sciences and Medicine, Volume: 5 Issue: 2. https://doi.org/10.32322/jhsm.1058324

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References (20)

  1. Sharma A, Stan MN. Thyrotoxicosis: diagnosis and management. Mayo Clin Proc 2019; 94: 1048-64.
  2. Kravets I. Hyperthyroidism: diagnosis and treatment. Am Fam Physician 2016; 93: 363-70.
  3. Sarkar SD. Benign thyroid disease: what is the role of nuclear medicine? Semin Nucl Med 2006; 36: 185-93.
  4. Pearce EN, Farwell AP, Braverman LE. Thyroiditis. New Engl J Med 2003; 348: 2646-55.
  5. De Leo S, Lee SY, Braverman LE. Hyperthyroidism. Lancet 2016; 388: 906-18.
  6. Alexander EK, Pearce EN, Brent GA, et al. 2017 Guidelines Of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and the postpartum. Thyroid 2017; 27: 315-89.
  7. Ross DS, Burch HB, Cooper DS, et al. 2016 American Thyroid Association Guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosis. Thyroid 2016; 26: 1343-421.
  8. Sencar ME, Çalapkulu M, Sakiz D, et al. Frequency of thyroid antibodies at the diagnosis of subacute thyroiditis. Turkish J Endocrinol Metab 2020; 24: 144-8.
  9. Barbesino G, Tomer Y. Clinical review: clinical utility of tsh receptor antibodies. J Clin Endocrinol Metab 2013; 98: 2247.
  10. Yoshimura Noh J, Momotani N, Fukada S, Ito K, Miyauchi A, Amino N. Ratio of serum free triiodothyronine to free thyroxine in graves’ hyperthyroidism and thyrotoxicosis caused by painless thyroiditis. Endocr J 2005; 52: 537-42.
  11. Izumi Y, Hidaka Y, Tada H, et al. Simple and practical parameters for differentiation between destruction-induced thyrotoxicosis and Graves’ thyrotoxicosis. Clin Endocrinol (Oxf) 2002; 57: 51-8.
  12. Shıgemasa C, Abe K, Tanıguchı S-I, et al. Lower serum free thyroxine (T4) levels in painless thyroiditis compared with Graves’ disease despite similar serum total T4 levels. J Clin Endocrinol Metab 1987; 65: 359-63.
  13. Tura Bahadır Ç, Yılmaz M, Kılıçkan E. Free triiodothyronine to free thyroxine ratio in the differential diagnosis of thyrotoxicosis and hyperthyroidism: a retrospective study. Int J Clin Pract 2021; 75: E14003.
  14. Narkar R, Mishra I, Baliarsinha A, Choudhury A. Rapid differential diagnosis of thyrotoxicosis using T3/T4 ratio, Ft3/Ft4 ratio and color doppler of thyroid gland. Indian J Endocrinol Metab 2021; 25: 193.
  15. Sriphrapradang C, Bhasipol A. Differentiating Graves’ disease from subacute thyroiditis using ratio of serum free triiodothyronine to free thyroxine. Ann Med Surg 2016; 10: 69-72.
  16. Wu Z, Zhu Y, Zhang M, et al. Serum ratio of free triiodothyronine to thyroid-stimulating hormone: a novel index for distinguishing Graves’ disease from autoimmune thyroiditis. Front Endocrinol (Lausanne) 2021; 11: 1-7.
  17. Sümbül HE, Acıbucu F. Graves’ disease and thyroiditis can be differentiated using only free thyroid hormone levels. Eur Res J 2019; 6: 314-8.
  18. Yanagisawa T, Sato K, Kato Y, Shimizu S, Takano K. rapid differential diagnosis of Graves’ disease and painless thyroiditis using total T3/T4 ratio, TSH, and total alkaline phosphatase activity. Endocr J 2005; 52: 29-36.
  19. Gilbert J. Thyrotoxicosis – investigation and management. Clin Med (Northfield Il) 2017; 17: 274-7.
  20. Chen X, Zhou Y, Zhou M, Yin Q, Wang S. Diagnostic values of free triiodothyronine and free thyroxine and the ratio of free triiodothyronine to free thyroxine in thyrotoxicosis. Int J Endocrinol 2018; 2018: 1-8.