[Thyroid echogeneity as a useful tool for the differential diagnosis of hyperthyroidism in the course of Graves...

Hashimoto's thyroiditis (HT) and Graves' disease (GD) constitute a spectrum of autoimmune thyroid diseases (AITD). They share an autoimmune pathogenesis, with a cellular and a humoral response to the thyroid gland. As a consequence, dysfunction of the gland itself may develop, characterized by hyperfunction in the case of GD and hypofunction in the case of HT, however at the onset of HT the hyperthyroidism might be observed as a result of a rapid destruction of thyrocytes. An abnormal thyroid echographic pattern characterized by a diffuse low echogeneity has been described in both AITD. This hypoechogeneity is due to three components: increase of intrathyroidal flow, functional changes in thyroid follicles with increased cellularity and decrease of the colloid content, resulting in the reduction of the cell/colloid interface, variable degree of lymphocytic infiltration. The first two components may be reversible during medical treatment and seem to be characteristic for GD, whereas lymphocytic infiltration may rather represent mostly HT. Here we present a 17-year-old girl with typical clinical signs of hyperthyroidism [firm goiter (II degrees), tachycardia, palpitations, nervousness, excessive sweating and tremor]. Laboratory tests were the following: fT3 - 6.59 pg/ml(increasing), fT4 - 1.99 ng/dl(increasing), TSH - 0.02 micro IU/ml(decreasing); anti-Tg-Ab - 840 IU/ml(increasing), anti-TPO-Ab - 190 IU/ml(increasing) (4 months later antithyroid antibodies were 2200 and 70, respectively). Ultrasound examination showed hypoechogeneity of the whole gland and enhanced vascular flow based on power Doppler analysis. Thyroid scan visualized the generally increased uptake of technetium. The girl was put on beta-blocker (propranolol) and later an antithyroid drug (thiamazole) was added. A course of disease was unstable, therefore the fine-needle aspiration biopsy was performed and showed the presence of single groups of normal thyrocytes and scanty colloid with no features of HT. Power Doppler analysis showed still enhanced blood flow within a gland inspite of euthyroid state. After a very unsteady period of the disease, the euthyroid state is maintained although the medical treatment was given up. The full recovery of normal blood flow and normal echogeneity of the thyroid was documented. The latter supports the diagnosis of GD. Follow-up of the thyroid echogeneity is of great diagnostic and prognostic value if the assay of TSHR-Ab is not available. On the other side, it has to be remembered that TSHR-Ab do not have to be positive in patients with GD and can be positive in patients with HT.