The relationship between overweight and thyroid function in first-episode, untreated Chinese patients with major depressive disorder with different ages of onset

•This is the first study to investigate the relationship between overweight and thyroid function varied with the age of onset and explore the related factors to overweight in first-episode, untreated Chinese patients with major depressive disorder(MDD) with different ages of onset. This study found that the relationship between overweight and thyroid function varied with the age of onset. Thyroid stimulating hormone was a factor related to overweight in both age of onset subgroups, and anti-thyroglobulin was associated with overweight in early adulthood onset MDD patients but not in mid-adulthood onset MDD patients. The influencing factors of overweight, such as cholesterol, systolic blood pressure and fasting blood glucose, also had different effects at different ages of onset. Major depressive disorder (MDD) and obesity are common. There are many differences in many aspects of MDD patients at different ages of onset (AOO); however, there are currently no studies on differences in obesity or overweight. This study aims to evaluate whether thyroid function changes with body weight, and to explore the related factors of overweight in MDD patients with different AOOs. A total of 1716 first-episode, untreated Chinese Han outpatients with MDD were recruited from a general hospital. Hamilton Anxiety Scale (HAMA), Hamilton Depression Scale (HAMD) and Positive Symptom subscale of the Positive and Negative Syndrome Scale (PANSS) were used to evaluate anxiety, depression and psychotic symptoms, respectively. The participants were divided into two groups: early adulthood onset (EAO, =45 years old). Compared with EAO patients, MAO patients scored higher on the HAMD, HAMA, CGI-S and PANSS positive symptoms subscale, and they also had higher systolic and diastolic blood pressure (BP), higher serum levels of thyroid stimulating hormone (TSH), FBG, cholesterol (TC) and low-density lipoprotein, but they had lower serum levels of free triiodothyronine 3 and high-density lipoprotein. TSH, anti-thyroglobulin (TgAb), TC and systolic BP were correlated with overweight in MAO patients, while TSH and FBG were correlated with overweight of EAO patients. The results indicate that TSH is related to overweight in both AOO subgroups, and the influencing factors of overweight related to thyroid function may be different in different AOOs.