We used a latent variable model to evaluate the association between estradiol and testosterone, and cerebral 5-HT4R binding based on [11C]SB207145 Positron Emission Tomography (PET) data from 25 males with MDD from the Neuropharm trial and 52 healthy males (aged 18–49), which included 38 healthy males from our previous study. The gene discussed is HTR4; the disease is major depressive disorder.