Sex differences in prevalence and clinical correlates of subclinical hypothyroidism in Chinese patients with first-episode untreated major depressive disorder.

Background: Previous studies showed sex differences in the prevalences of both major depressive disorder (MDD) and subclinical hypothyroidism (SCH). This study aimed to further compare the prevalence and correlates of moderate-to-severe SCH between male and female Chinese MDD patients.

Methods: A total of 1706 first-episode drug naïve Chinese patients with MDD were recruited. Depressive symptoms were assessed by the 17-item Hamilton Depression Rating Scale, psychotic symptoms by the Positive and Negative Syndrome Scale and anxiety symptoms by the Hamilton Anxiety Rating Scale. Serum thyroid stimulating hormone (TSH), free triiodothyronine (fT3) and free thyroxine (fT4) concentrations were measured by chemiluminescence immunoassay. Moderate-to-severe SCH was defined as serum TSH > 8 mIU/L with normal fT4.

Results: The prevalence of moderate-to-severe SCH was 10.4% in male patients and 15.1% in female patients (χ2 = 7.22, p < 0.01). In female patients, binary logistic regression showed that systolic blood pressure (SBP), suicide attempts and psychotic symptoms (all p < 0.001) were associated with moderate-to-severe SCH. In male patients, SBP and psychotic symptoms were associated with moderate-to-severe SCH (both p < 0.001), while suicide attempts and severe anxiety were not (p > 0.05).

Conclusions: Our findings reveal a higher prevalence rate of moderate-to-severe SCH in female untreated first-episode MDD patients compared with males. Moreover, there is a positive association between suicide attempts and moderate-to-severe SCH only in female MDD patients.