Thyroid echogenicity in manic-depressive patients receiving lithium therapy

Background: Lithium is known to induce subclinical or overt hypothyroidism and changes of thyroid volume in manic-depressive patients. Little is known about alterations of thyroid echogenicity due to drug-induced dysfunction. Methods: Twenty manic-depressive patients receiving lithium therapy for at least 6 months and 20 euthyroid volunteers without any antidepressive medication as control group, matched in age and gender, were investigated by laboratory measurements and thyroid ultrasonography including standardized grey scale analyses in representative regions of interest (ROI). Results: Thyroid function was normal in all patients (mean FT4 1.1±0.2 ng/dl, mean TSH 1.6±0.9 μ U/ml) and controls (mean FT4 1.5±0.4 ng/dl, TSH 1.1±0.3 μ U/ml). Except for two patients, no thyroid autoantibody levels could been detected. Thyroid volumetry revealed significant higher mean values for the lithium treated patients (16.9±11.9 ml) compared with the controls (11.4±4.5 ml, P<0.05) with a considerable number of goiters (six patients vs. one control). Thyroid echogenicities in both groups were similar (patients 23.9±3.7 grey scales, Grauwerteinheiten=GWE, controls 24.2±1.3 GWE) and did not depend on the size of the organs. Conclusion: Lithium treatment contributes to increased thyroid volumes, probably due to inhibition of thyroid function and TSH upregulation, but not to changes of thyroid echo levels in patients with still euthyroid function. Further echogenicity studies on patients with lithium-induced overt hypothyroidism and autoimmune activity will be of special interest.