Figure 1.

Sex chromosomes (XX=female; XY=male) determine which gonads will form and which sex hormones (mainly testosterone, estradiol, and progesterone) they will produce. Fetal testosterone is important for permanent masculinization of the male brain and body during the organizational period (late gestation/birth, in rodents). This is the proposed period for vulnerability to ND. Sex hormones then surge during the activational period (puberty) for more transient effects; males have relatively stable testosterone levels, and females have variable hormone levels over the 4–5 day estrous cycle. Modified from [54].