Ultrasonically determined thyroid volume and thyroid functions in lithium-naïve and lithium-treated patients with bipolar disorder: a cross-sectional and longitudinal study.

Objective: This study investigated thyroid volume, hormone levels and antibodies in long-term lithium-treated and lithium-naïve bipolar patients, some of whom underwent prospective follow-up evaluations.

Methods: Fourteen lithium-naïve patients, 13 long-term lithium-treated patients diagnosed with bipolar disorder and 12 healthy controls were included. Seven lithium-naïve patients were followed-up during their lithium receiving period (range 6-9 months). Thyroid volume and serum levels of thyroid hormones and antibodies were measured once in the long-term lithium-treated patients and controls, and twice in the lithium-naïve patients, i.e. before and after lithium treatment.

Results: Mean thyroid volumes in the lithium-naïve patients were significantly higher than those in the controls. Long-term lithium-treated patients had significantly higher total thyroid volume than the lithium-naïve patients and the controls. Total thyroid volume in the patients after the lithium treatment was significantly higher than that before. Serum free thyroxine (fT4) levels in the long-term lithium-treated patients were lower than those in the lithium-naïve patients and the controls. In the lithium-naïve patients, after lithium treatment, free triiodothyronine (fT3) levels were lower, and thyroid stimulating hormone (TSH) levels were higher compared to those before lithium treatment.

Conclusions: The results suggest that thyroid enlargement and some alterations in thyroid hormones in bipolar patients may present even before lithium treatment and increase further with lithium treatment.