Use of color Doppler ultrasonography to measure thyroid blood flow and differentiate graves' disease from painless thyroiditis.

BACKGROUNDS: Color Doppler ultrasonography (CDU) has not yet been established as a method to investigate the pathogenesis of thyrotoxicosis. OBJECTIVES: Our first objective was to determine whether the measurement of peak systolic blood-flow velocity in the superior thyroid artery (STV) and thyroid tissue blood flow (TBF) using CDU could differentiate Graves' disease (GD) from painless thyroiditis (PT). The second objective was to examine the factors mediating increased blood flow to the thyroid gland in GD. METHODS: Recruited patients had untreated GD or PT and visited the Department of Internal Medicine (I), Osaka Medical College, between April 1, 2006 and May 31, 2010. Age, gender, blood pressure, pulse rate, thyroid-stimulating hormone, free thyroxine, tri-iodothyronine, TSH receptor antibody and thyroid volume were evaluated in patients. In addition, bilateral measurements of STV, TBF and peak systolic velocity in the common carotid artery (CCV) were also performed. TBF was quantified by calculating the ratio of blood-flow pixels to total pixels in the region of interest using sagittal section images of the thyroid gland. Receiver-operating characteristic curve analysis was performed to determine the ability of STV and TBF measurements to differentiate GD from PT. RESULTS: For the average of STV measured on both sides, the area under the receiver-operating characteristic curve (AUC) was 0.956. For the average of TBF measured on both sides, the AUC was 0.920. At an average STV cut-off value of 43 cm/s, the sensitivity to discriminate GD from PT was 0.87 and the specificity was 1.00. At an average TBF cut-off value of 3.8%, the sensitivity was 0.71 and the specificity was 1.00. In the GD group, neither blood pressure nor pulse rate correlated with the average STV or TBF. Moreover, there was no correlation between STV and CCV or between TBF and CCV on either side. However, STV was correlated with TBF (right side: R = 0.47; left side: R = 0.52). CONCLUSIONS: The results demonstrate that STV and TBF are useful for differentiating GD from PT. Furthermore, the increased STV and TBF found in GD are not related to hyperthyroidism-induced increases in systolic blood pressure, pulse rate or CCV.

The prevalence of polycystic thyroid disease in hypothyroid patients with negative thyroid autoantibodies.

BACKGROUND: We previously reported that multiple thyroid cysts may be a cause of hypothyroidism in patients with a relatively high iodine intake and we termed it polycystic thyroid disease (PCTD). The aim of this study was to investigate the prevalence of PCTD in patients who visited our thyroid center. We hypothesized that patients with PCTD are not rare in a region with a high iodine intake. METHODS: We retrospectively studied the cause of hypothyroidism based on medical histories and ultrasonography in new patients to our hospital from April 2008 to March 2009 whose serum tests for antithyroglobulin antibodies (TgAb) and thyroid peroxidase antibodies (TPOAb) were negative. Serum thyroid hormones, thyrotropin (TSH), TgAb, and TPOAb were measured in 8243 patients. Patients with four or more thyroid cysts, negative tests for TgAb and TPOAb, no evidence for thyroid diseases other than their thyroid cysts, and no exposure to thyroid-perturbing influences were defined as having PCTD. RESULTS: Three hundred seven patients had overt hypothyroidism (TSH level above 10.0 µU/mL and free thyroxine level below 0.7 ng/dL), of whom 71 patients were both TgAb and TPOAb negative. There were 546 patients with subclinical hypothyroidism (TSH level above 5.0 µU/mL and normal free thyroxine), of whom 193 patients were both TgAb and TPOAb negative. There were 24 patients with overt hypothyroidism and PCTD, accounting for 7.8% (24/307) of all causes of overt hypothyroidism. There were 42 patients with subclinical hypothyroidism and PCTD, accounting for 7.7% (42/543) of all causes of subclinical hypothyroidism. PCTD was more common among elderly people than young people. CONCLUSIONS: PCTD appears to be a minor but not negligible cause of hypothyroidism, at least in iodine-rich regions. PCTD with hypothyroidism may have been misdiagnosed as thyroid antibody-negative Hashimoto's thyroiditis in many reports.

Multiple thyroid cysts may be a cause of hypothyroidism in patients with relatively high iodine intake.

BACKGROUND: Multiple cysts of the thyroid gland have not been recognized as one of the causes of hypothyroidism. Here we present six patients from a region with relatively high iodine intake in whom multiple cysts of the thyroid were associated with hypothyroidism or the development of hypothyroidism. SUMMARY: All patients were women and ranged in age from 49 to 71. Their thyroids were mildly enlarged, tests for thyroid autoantibodies were negative, and multiple cysts were detected in the thyroid by ultrasonography. By dietary questionnaire their iodine intake was estimated to range from 2 to 10 mg of iodine daily. Otherwise, there was no evidence for disorders or factors associated with hypothyroidism. All four patients who agreed to dietary iodine restriction became euthyroid at approximately 1 month after a low-iodine diet (less than 0.5 mg iodine per day) was started. CONCLUSIONS: Although these patients were from a region with high-iodine intake and had a relatively high intake compared with most regions of the world, this amount of iodine intake is not associated with hypothyroidism in otherwise healthy persons. Therefore, we propose that multiple thyroid cysts, which we have termed polycystic goiter, is probably a cause of hypothyroidism in patients with a relatively high iodine intake.