Color-flow doppler sonography in patients with subclinical thyroid dysfunction.

OBJECTIVE

To assess the value of color-flow Doppler sonography (CFDS) in evaluating intrathyroidal blood flow and velocity in patients with subclinical thyroid dysfunction.

METHODS

In this prospective study, patients with subclinical hypothyroidism, patients with subclinical hyperthyroidism, and euthyroid patients without known thyroid autoimmune disease who served as controls were included. Subclinical thyroid dysfunction was defined as normal se-rum free thyroxine (FT4) and free triiodothyronine (FT3) in the presence of high (subclinical hypothyroidism), or low-suppressed (subclinical hyperthyroidism) serum thyrotropin (TSH) levels. Serum FT4, FT3, TSH, and antibodies to thyroid peroxidase and thyroglobulin were measured in all participants. In addition, TSH receptor antibody levels were determined in patients with subclinical hyperthyroid-ism. All participants underwent conventional sonography and CFDS. Mean peak systolic velocity (PSV) and resistive index were obtained from multiple extranodular thyroid parenchyma samplings and inferior thyroid artery measurements.

RESULTS

The study population included 27 patients with subclinical hypothyroidism, 15 patients with subclinical hyperthyroidism, and 20 euthyroid patients. Patients with subclinical hypothyroidism had significantly higher mean intrathyroidal PSV values than control patients (19.9 +/- 5.6 cm/s vs 15.7 +/- 4.4 cm/s; P = .008), whereas patients with subclinical hyperthyroidism had significantly higher mean PSV values than control patients at the inferior thyroid artery level (29.7 +/- 10.7 cm/s vs 21.9 +/- 6.8 cm/s; P = .014). Compared with control patients, a greater proportion of patients with subclinical hypothyroidism and patients with subclinical hyperthyroidism had marked CFDS patterns (78% vs 15% [P<.001] and 53% vs 15%; [P<.001], respectively). A significant association was found between positivity for thyroid autoantibodies and intense CFDS patterns. No correlation was found between TSH or thyroid hormone levels and CFDS pattern or blood flow velocity.

CONCLUSION

We have demonstrated that significantly increased thyroid blood flow velocity and vascularity are already present in patients with mild thyroid dysfunction.