Thyroid structure and function in long-term lithium-treated and lithium-naïve bipolar patients.

OBJECTIVE: The aim of the study was to compare the structure and function of the thyroid in patients with bipolar disorder (BD) receiving long-term lithium treatment, with BD patients never receiving lithium.

METHODS: Ninety-eight patients (68 female and 30 male), aged 62 ± 13 years, receiving lithium for 3-47 years (mean 19 ± 10 years), and 39 patients (27 female and 12 male), aged 57 ± 10 years, receiving other mood-stabilizing drugs but never treated with lithium, were included. The thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), and free thyroxine (fT4) were estimated, and the ultrasonographic study of the thyroid gland was performed.

RESULTS: Compared with patients not receiving lithium, lithium-treated patients had significantly higher concentrations of TSH and fT4 and the lower concentration of fT3. However, the percentage of hypothyroidism was not different in both groups. Lithium-treated patients also had significantly higher thyroid volume, the higher number of focal changes >1 cm, and more frequent goiter. The structural changes were not related to the hormones' concentrations.

CONCLUSIONS: The results show a significant association between long-term lithium treatment and the increase of TSH and fT4, the decrease of fT3, higher thyroid volume, and more frequent goiter and nodular goiter. The effect of lithium on thyroid structure was not associated with its effect on thyroid hormones.