VALUE OF THYROID ECHOGRAPHY IN THE LONG-TERM FOLLOW-UP OF LITHIUM-TREATED PATIENTS

Psychiatric patients on long-term lithium (Li) therapy frequently deve lop goiter and/or hypothyroidism. It has also been suggested that Li m ay trigger/exacerbate thyroid autoimmunity. Previous studies provided evidence that underlying thyroid diseases represent important predispo sing factors for the development of Li-induced thyroid dysfunction. Th e aim of the present paper was to assess the value of thyroid ultrasou nd - a simple and reliable tool to detect subtle thyroid abnormalities - in the longitudinal evaluation of 23 Li-treated psychiatric patient s without evidence of biochemical thyroid abnormalities before therapy . For this purpose, thyroid ultrasound was associated with a clinical and laboratory (serum thyroxine, serum triiodothyronine, serum TSH, an tithyroglobulin (AbTg), antithyroid microsomal (AbM) and antithyroid p eroxidase autoantibodies) evaluation prior to and at 6- to 12-month in tervals during Li treatment. On the basis of thyroid ultrasound before Li, patients were subdivided into two groups: group A (n = 15, 7 male s, 8 females) with a normal echography and group B (n = 8, 5 males, 3 females) with mild ultrasound abnormalities. In group A the developmen t of a small diffuse goiter was confirmed by physical examination duri ng Li therapy; 2 patients displayed a transient increase of serum TSH concentration and none developed detectable serum antithyroid autoanti bodies. Beside the small volumetric increase, no other ultrasound abno rmalities were observed during the entire follow-up. In all group B pa tients a mild diffuse goiter was clinically detected before and on Li administration and no significant Volumetric changes were observed dur ing follow-up. Two patients developed high titers of AbM and AbTg 12 a nd 1 s months after the beginning of Li, respectively; in 1 a persiste nt increase of serum TSH concentration was also observed. Thyroid echo graphy before Li displayed different degrees of scattered or diffuse h ypoechogenicity and a further decrease in echogenicity was detected du ring Li therapy in 2 patients. In conclusion, we provided further evid ence that longterm Li administration is not associated with de novo ap pearance of thyroid autoimmune phenomena in humans, but rather with an exacerbation of underlying thyroid autoimmunity. In addition to thyro id autoantibody and TSH measurements, thyroid echography appears to be a sensitive tool in the identification of patients at risk of develop ing autoimmune hypothyroidism during long-term Li therapy.