Endocrinol Metab.  2012 Jun;27(2):121-125. 10.3803/EnM.2012.27.2.121.

Differential Diagnostic Value of Total T3/Free T4 Ratio in Graves' Disease and Painless Thyroiditis Presenting Thyrotoxicosis

• Lee SM
• Kim SK
• Hahm JR
• Jung JH
• Kim HS
• Kim S
• Chung SI
• Choi BH
• Jung TS

• KMID: 1497650
• DOI: http://doi.org/10.3803/EnM.2012.27.2.121

Abstract

BACKGROUND
It is important to differentiate Graves' disease from that of painless thyroiditis in patients with thyrotoxicosis. In this study, we evaluated the usefulness of total T3 to free T4 ratio in making a differential diagnosis between Graves' disease and painless thyroiditis.
METHODS
We reviewed medical records of thyrotoxic patients, who had been diagnosed with Graves' disease or painless thyroiditis, from October 2009 to July 2011. We assessed clinical characteristics, serum levels of total T3, free T4, thyroid stimulating hormone, thyrotropin-binding inhibitory immunoglobulin, and findings of 99mTechnetium thyroid scan. We analyzed the total T3/free T4 ratios between Graves' disease and painless thyroiditis patients.
RESULTS
A total of 76 untreated thyrotoxic patients "49 Graves' disease and 27 painless thyroiditis" were examined. The total T3, free T4 levels and the total T3/free T4 ratios were significantly higher in patients with Graves' disease than in those with painless thyroiditis (P < 0.001). In the total T3/free T4 ratio > 73, the possibility of Graves' disease was significantly higher than in painless thyroiditis (sensitivity, 75.5%; specificity, 70.3%). The sensitivity and specificity of the total T3/free T4 ratio in patients with free T4 < 3.6 ng/dL have been increased (sensitivity, 100%; specificity, 71.4%).
CONCLUSION
The total T3/free T4 ratios was useful for making a differential diagnosis between Graves' disease and painless thyroiditis.

Keyword

Graves' disease; Painless thyroiditis; Thyrotoxicosis; Total T3/free T4 ratio

MeSH Terms

Diagnosis, Differential
Graves Disease
Humans
Immunoglobulins
Immunoglobulins, Thyroid-Stimulating
Medical Records
Sensitivity and Specificity
Thyroid Gland
Thyroiditis
Thyrotoxicosis
Thyrotropin
Immunoglobulins
Immunoglobulins, Thyroid-Stimulating
Thyrotropin

Figure

• 

  Fig. 1 Individual serum total T3/free T4 ratios in Graves' disease and painless thyroiditis. Total T3/free T4 ratio in patients with Graves' disease was significantly (P < 0.001) higher than that in patients with painless thyroiditis.

• 

  Fig. 2 Relationship between total T3/free T4 ratio and free T4 value in patients with Graves' disease and painless thyroiditis. Upper-left areas above the line represent the total T3/free T4 ratio of > 73. The ratios in the Graves' disease groups increased as the free T4 values decreased.

• 

  Fig. 3 Individual serum total T3/free T4 ratios of free T4 < 3.6 ng/dL group and free T4 > 3.6 ng/dL group with Graves' disease and painless thyroiditis. The total T3/free T4 ratios were significantly higher in free T4 < 3.6 ng/dL group with Graves' disease. Upper areas above the line represent the total T3/free T4 ratio of > 73.

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