The effect of long-term lithium administration on thyroid function and structure as compared with monotherapy by other mood stabilising drugs – a preliminary study
Aims: Long-term treatment with lithium in patients with bipolar disorder (BD) exerts a significant effect on thyroid structure and function. Previously, it was found that adding to lithium other mood stabilising or antidepressant drugs can also be important. The aim of this preliminary study was to compare thyroid structure and function in patients with BD receiving long-term lithium monotherapy with monotherapy using other mood stabilising drugs, such as carbamazepine, valproates or quetiapine.
Method: Forty-one BD patients were studied (13 male, 28 female) aged 28–80 years. In 15, monotherapy with lithium was given; in 10 – with carbamazepine; and in 8 – with valproate and quetiapine. In all patients, the thyroid-stimulating hormone (TSH), free thyroxine (fT3) free triiodothyronine (fT4), and the antibodies against thyroid peroxidase (TPOAb), thyroglobulin (TGAb) and TSH receptors (TSHRAb) were estimated. Goiter was diagnosed when the thyroid volume exceeded 18 cm3 in women and 25 cm3 in men.
Results: The groups were of similar age; however, the duration of quetiapine therapy was shorter than lithium or carbamazepine. Comparing to patients on lithium monotherapy, the median of TSH concentration was lower in patients on quetiapine, and the median of TPOAB lower in patients on valproates. The highest frequency of goiter (47%) was observed in patients receiving lithium.
Conclusions: The results obtained may suggest that among the studied mood stabilisers, lithium exerts the biggest goiter-inducing effect. The differences between groups as to thyroid hormones and antibodies were not significant. The limitation of the study was a small number of studied patients.