Although the vast majority of people with depression do not exhibit hypothyroidism, abnormal T4 to T3 ratios, elevated reverse T3 (rT3) levels, blunted TSH responses to TRH, and the presence of antithyroid antibodies are reported to be more common in people with depression than in the general population (Hage and Azar, 2012; Pilhatsch et al., 2014). This evidence concerns the gene TRH and major depressive disorder.