Dose-responses association of acute phase quetiapine treatment with risk of new onset hypothyroidism in schizophrenia patients.

Zhao, Ying; Wen, Shi Wu; Li, Mengzhe; Sun, Zhongyu; Yuan, Xiang; Retnakaran, Ravi; Zhang, Ruiling; Zhai, Desheng

AIM To assess association between quetiapine treatment and risk of new onset hypothyroidism in schizophrenia patients. METHODS We conducted a retrospective cohort study in a tertiary hospital in China between January 2016 and December 2018. Schizophrenia patients with normal thyroid tests at admission were included. Hypothyroidism, which was defined as TSH>4.20 mU/L and free T4<12.00 pmol/L, or on L- thyroxine prescriptions, was the outcome measure, and quetiapine treatment between admission and subsequent thyroid test was the exposure measure of this study. Adjusted relative risks and 95% confidence intervals were used to assess the independent association of quetiapine treatment with risk of new onset hypothyroidism. The dose-response association was further analyzed by three quetiapine doses: low (<=0.2 g/d), medium (0.2-0.6 g/d), and high (>0.6 g/d). RESULTS A total of 2,022 eligible patients were included in the final analysis. Sixty patients (15.0%) in the quetiapine group developed hypothyroidism, while 56 patients (3.5%) in non-quetiapine group developed hypothyroidism. Relative risk (95% confidence interval) of developing hypothyroidism for quetiapine use was 4.01 (2.86-5.64) after adjusting for a number of potential confounding factors. A strong dose-response association between quetiapine use and risk of developing hypothyroidism was observed: adjusted relative risks (95% confidence intervals) were 1.00 (0.25-2.59), 4.22 (2.80-6.25), and 5.62 (3.66-8.38), respectively, for low-, medium-, and high-dose quetiapine, as compared with no quetiapine. CONCLUSION Acute phase quetiapine treatment for schizophrenia patients was strongly associated with increased risk of developing new onset hypothyroidism, with a clear dose-response association.