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.
Keywords: mirtazapine, thyroid function, hypothyroxinemia,
major depressive disorder, acute episode