Quantitative measurement of thyroid blood flow for differentiation of painless thyroiditis from Graves' disease

• Published in: Clinical endocrinology (Oxford) Vol. 67; no. 1; pp. 41 - 45
• Main Authors: Ota, Hisashi, Amino, Nobuyuki, Morita, Shinji, Kobayashi, Kaoru, Kubota, Sumihisa, Fukata, Shuji, Kamiyama, Naohisa, Miyauchi, Akira
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-07-2007; Blackwell
• Subjects: Adolescent; Adult; Aged; Biological and medical sciences; Case-Control Studies; Diagnosis, Differential; Endocrinopathies; Female; Fundamental and applied biological sciences. Psychology; Graves Disease - diagnosis; Humans; Iodine Radioisotopes - pharmacokinetics; Linear Models; Male; Medical sciences; Middle Aged; Non tumoral diseases. Target tissue resistance. Benign neoplasms; Radionuclide Imaging; Regional Blood Flow; Statistics, Nonparametric; Thyroid Function Tests; Thyroid Gland - blood supply; Thyroid Gland - diagnostic imaging; Thyroid Hormones - blood; Thyroid. Thyroid axis (diseases); Thyroiditis - diagnosis; Ultrasonography, Doppler, Pulsed; Vertebrates: endocrinology; Endocrinopathy; Measurement; Thyroiditis; Immunopathology; Endocrine gland; Hyperthyroidism; Thyroid diseases; Autoimmune disease; Cell differentiation; Blood flow; Graves disease; Hemodynamics; Differentiation; Endocrinology; Quantitative analysis
• ISSN: 0300-0664; 1365-2265
• DOI: 10.1111/j.1365-2265.2007.02832.x

Summary
Objective  Differentiation between destruction‐induced thyrotoxicosis and Graves’ thyrotoxicosis is important for selection of proper therapy. It is, however, often difficult to make this distinction without measurement of radioactive iodine uptake. We investigated the possibility that assessment of thyroid blood flow would allow differentiation between the two entities.
Patients and measurements  One hundred and fourteen untreated patients with thyrotoxicosis (56 Graves’ disease, 28 painless thyroiditis, 30 subacute thyroiditis) and 25 normal controls were examined. Serum levels of freeT4 (FT4), freeT3 (FT3) and TSH were measured by chemiluminescent immunoassay, and anti‐TSH receptor antibodies (TSH‐binding inhibitory immunoglobulin, TBII) were measured by enzyme‐linked immunosorbent assay. Thyroid volume and blood flow (TBF) were measured quantitatively by ultrasonography.
Results  TBF was significantly higher in Graves’ disease (mean ± 1SD: 14·9 ± 6·4%, P < 0·0001) than in painless thyroiditis (0·8 ± 0·5%), subacute thyroiditis (0·9 ± 0·7%) and in normal controls (0·8 ± 0·5%). All patients with Graves’ disease had TBF values of more than 4% and all patients with painless thyroiditis and subacute thyroiditis had TBF values less than 4%. TBF values significantly correlated with values of radioactive iodine uptake (RAIU) either at 3 h (r = 0·492, P < 0·01) or 24 h (r = 0·762, P < 0·001) within the Graves’ disease and painless thyroiditis groups. There was no relationship between TBF values and thyroid volumes or values of TBII in the Graves’ disease group. All patients with Graves’ disease had positive TBII of 15% or more. Three of 28 patients with painless thyroiditis and one of 30 patients with subacute thyroiditis had positive TBII.
Conclusion  TBF was quantitatively measured by power Doppler ultrasonography and was more effective than TBII for differentiation between destruction‐induced thyrotoxicosis (painless or subacute thyroiditis) and Graves’ thyrotoxicosis. TBF values of less than 4% in untreated thyrotoxic patients are laboratory signals of destruction‐induced thyrotoxicosis and if these are determined, the radioactive iodine uptake test can be omitted for differential diagnosis of these two types of thyrotoxicosis.