Mirtazapine use may increase the risk of hypothyroxinemia in patients
affected by major depressive disorder
Abstract
Background Hypothyroxinemia, i.e. Low free T4 with normal TSH level,
which overlaps, to a great extent, with the laboratory criteria of
central hypothyroidism, could be easily neglected, if attention is paid
only to patients with elevated TSH. We aimed to assess the association
between mirtazapine use and hypothyroxinemia in patients affected by
major depressive disorder. Methods We conducted a retrospective cohort
study in the Second Affiliated Hospital of Xinxiang Medical University
between January 2016 and December 2018. Patients affected by major
depression disorder and admitted to the hospital for treatment during
the study period and had thyroid tests at admission and after treatment
were included. Patients with abnormal thyroid function at baseline or
received mood stabilizers or quetiapine during hospitalization were
excluded. Mirtazapine use was the exposure measure, and hypothyroxinemia
was as the primary outcome of this study. Log-binomial model was used to
estimate the association between mirtazapine use and hypothyroxinemia,
after adjusting for potential confounding factors. Results A total of
220 eligible patients were included in the final analysis. Of them, 88
used mirtazapine. The incidence of hypothyroxinemia in patients who used
mirtazapine was higher (37.5%) than those patients who did not use
(19.7%). The relative risk of developing hypothyroxinemia was 1.64
(95% confidence interval: 1.31-1.78) for mirtazapine use, after
adjusting for confounding factors. Conclusion Mirtazapine use was
associated with the risk of developing hypothyroxinemia. Clinicians
should be aware that hypothyroxinemia may be neglected in patients
treated by mirtazapine due to attention paid only to those with elevated
TSH.