Assessment of Serum Tri-Iodothyronine (T3), Thyroxin (T4) and Thyroid-Stimulating Hormone (TSH) Levels Among Patients With Major Depressive Disorder (MDD) in Hamedan, Northwestern Iran

Depression is one of the most common psychiatric disorders. Over the last few years, the relationship between the hypothalamic-pituitary-thyroid (HPT) axis and depression has been the focus of increasing attention.
In this study, the serum levels of T3, T4, and TSH in patients with major depressive disorder have been compared to the healthy adults in Hamedan, northwestern Iran.
Patients and In this case-control study, serum levels of T3, T4, and TSH were measured in 32 patients with major depression, diagnosed according to the beck depression inventory (BDI), who were referred to the Hamedan psychiatric hospital and were age- and sex-matched normal adults. Sampling was conducted through convenience sampling in a completely randomized design. Data were analyzed using an independent t-test and a one-way analysis of variance (ANOVA) test. A logistic regression model was used for depression occurrence probability prediction.
Serum T4 and TSH levels were significantly higher in depressive patients than in the control group (P = 0.01), whereas there was no significant difference in T3 serum levels between the two groups (P = 0.08). The serum TSH level was significantly higher in depressive patients compared to non-depressive patients (P = 0.001). According to logistic regression analysis, a one unit increase in serum T4 or TSH levels may enhance non-clinical depression probability by 1.3 or 1.7 times and clinical depression probability by 1.2 or 2.9 times, respectively.
Serum T4 and TSH levels in depressive patients were found to be significantly higher than those of the control group, indicating the association between serum T4 and TSH levels and depression in the subjects in 2010 - 2011 in Hamedan, northwestern Iran.