A case of
hyperthyroidism occurring in a 68 year old man receiving
lithium carbonate (1 g/day) for 5 years is reported. The clinical history of the patient, treated for bipolar
affective disorder, was remarkable for transient
hypothyroidism followed several months later by
tremor, increased free
thyroxine and
triiodothyronine, and decreased TSH levels which led to
lithium withdrawal. Two months later, clinical and
biological signs were unchanged, Tc99m-scan displayed a homogeneous and increased
isotope uptake. In this setting, high levels of
autoantibodies against
TSH-receptor, and grade I
exophthalmos and slightly ocular muscle enlargement at CT-scan favored the diagnosis of
Graves' disease (perhaps facilitated by
lithium therapy).
Carbimazole treatment was effective in controlling
hyperthyroidism. Review of the literature disclosed 44 cases of
hyperthyroidism occurring in
lithium-treated patients. Most of these cases concerned specific
thyroid diseases, particularly with an autoimmune mechanism. There is also evidence for an actual role of
lithium in increasing intrathyroid
iodide pool and for an impact of
lithium on the immune system. Thus, the hypothesis that
lithium may trigger the development of an autoimmune
thyroid disease in predisposed patients deserves further investigation.