GDF15 and depressive symptom measurement: As shown in Table 3 and Figure 2, after an adjustment for family history of depression, smoking, age, and traumatic life events, HAMD-24 scores were positively correlated with GDF-15 serum levels (β-coefficient = 0.248, p < 0.01) but not with T levels (β-coefficient = −0.141), E2 levels (β-coefficient = −0.023), and the T/E2 ratio (β-coefficient = −0.125) (all p > 0.05).