Grey-scale analysis allows a quantitative evaluation of thyroid echogenicity in the patients with Hashimoto's thyroiditis.

OBJECTIVE

In the present study we have performed a grey-scale quantitative analysis of thyroid echogenicity in the patients affected by Hashimoto's thyroiditis (HT), obtaining a numerical estimate of the degree of hypoechogenicity associated with the appearance of thyroid dysfunction.

MATERIALS AND METHODS

The study group included 89 patients with serum positivity for thyroglobulin (TgAb) and/or peroxidase (TPOAb) antibodies. Ultrasound (US) evaluation of thyroid gland and biochemical assay of serum thyrotropin (TSH), free-thyroxine (FT4) and free-triiodiothyronyne (FT3) were performed in all patients, and in 40 healthy subjects enrolled as control group. Thyroid echogenicity was compared with that of the surrounding neck muscles, using the grey-scale histogram analysis. The echogenicity was expressed in grey-scales (GWE).

RESULTS

In HT patients, the mean of thyroid echogenicity was lower when compared to the normal thyroid (61.9 +/- 8.3 GWE vs. 71.9 +/- 3.1 GWE; P = 0.01). In all HT patients the lowest limit of thyroid echo distribution was in the echogenicity range of the surrounding muscle, the overlapping ranging between 3.4% and 95.0% (mean +/- SD 48.4 +/- 20.9%). The extension of like-muscle hypoechogenicity into the thyroid gland was significantly correlated with serum TSH values (r = 0.37; P < 0.001), serum FT4 values (r = -0.60; P < 0.001), and serum TPOAb values (r = 0.31; P = 0.004). Nobody was hypothyroid when the hypoechogenicity was less than 38.0%, whereas hypothyroidism occurred in all cases with hypoechogenicity of more than 68.9%. The receiving operating characteristic curve demonstrated that 48.3% was the best cut-off for identifying hypothyroid patients with sensitivity, specificity and diagnostic accuracy of 88.9%, 86.3% and 87.6%, respectively.

CONCLUSIONS

In conclusion, the grey-scale quantitative analysis has provided a measure of thyroid hypoechogenicity associated with the appearance of hypothyroidism during the course of HT. The results of the present study would encourage the application of the computerized grey-scale analysis as complementary tool to US evaluation in the patients affected by HT.