Graves’ disease and thyroiditis can be differentiated using only free thyroid hormone levels

Objectives: As the treatment approaches of Graves’ disease and thyroiditis are different, differential diagnosis is important. In this study, we analyzed whether it is possible to perform a differential diagnosis for these two conditions by checking the increase ratio of free thyroid hormones.Methods: In total 156 patients were taken into this study of which 29 were thyroiditis (17 had subacute thyroiditis, 6 had post-partum and 6 had silent thyroiditis) and 127 were Graves patients. The age, free T3 (FT3), free T4 (FT4), thyroid stimulating hormone (TSH) levels, FT3 index (FT3/FT3 upper limit of normal (ULN)), FT4 index (FT4/FT4 ULN) and free thyroid hormone index (FTHI) (FT3 index/FT4 index) of all patients were determined.Results: A significant difference was found between the mean TSH, FT3 and FT3 index between Graves’ disease and thyroiditis (p = 0.036, p = 0.001 and p =0.001, respectively). When the groups were compared in terms of FTHI, the difference was found statistically significant (p = 0.001). FTHI was above 1 in all patients with Graves’ disease whereas it was found below 1 in all patients with thyroiditis. There were no statistically significant difference between the Graves’ disease and the thyroiditis in terms of age, FT4 and FT4 index (p = 0.748, p = 0.389 and p = 0.392, respectively).Conclusion: Based on these results, considering the increases in free thyroid hormone values we can say that it is possible to perform a differential diagnosis of Graves’ disease and thyroiditis, and that this may be used as a practical method to differentiate these two conditions.

Keywords:

Graves’ disease thyroiditis, free thyroid hormone index,

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1. Devereaux D, Tewelde SZ. Hyperthyroidism and thyrotoxicosis. Emerg Med Clin N Am 2014;32:277-92.
2. Franklyn JA, Boelaert K. Thyrotoxicosis. Lancet 2012;379:1155-66.
3. Grigoriu C, Cezar C, Grigoras M, Horhoianu I, Parau C, Vîrtej P, et al. Management of hyperthyroidism in pregnancy. J Med Life 2008;1:390-6.
4. Cooper DS, Laurberg P. Hyperthyroidism in pregnancy. Lancet Diabetes Endocrinol 2013;1:238-49.
5. Menconi F, Marcocci C, Marinò M. Diagnosis and classification of Graves' disease. Autoimmun Rev 2014;13:398-402.
6. Bahn Chair RS, Burch HB, Cooper DS, Garber JR, Greenlee MC, Klein I, et al.;American Thyroid Association; American Association of Clinical Endocrinologists. Hyperthyroidism and other causes of thyrotoxicosis: management guidelines of the American Thyroid Association and American Association of Clinical Endocrinologists. Thyroid. 2011;21:593-646.
7. Samuels MH. Subacute, silent, and postpartum thyroiditis. Med Clin North Am 2012;96:223-33.
8. Woolf PD. Transient painless thyroiditis with hyperthyroidism: a variant of lymphocytic thyroiditis? Endocr Rev 1980;1:411-20.
9. Bogazzi F, Vitti P. Could improved ultrasound and power Doppler replace thyroidal radioiodine uptake to assess thyroid disease? Nat Clin Pract Endocrinol Metab 2008;4:70-1.
10. Gorman CA. Radioiodine and pregnancy. Thyroid 1999;9:721-6.
11. Shigemasa C, Abe K, Taniguchi S, Mitani Y, Ueda Y, Adachi T, 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.
12. Dufour DR. Laboratory tests of thyroid function: uses and limitations. Endocrinol Metab Clin N Am 2008;36:579-94.