Your thalamus is like the manager of your brain. All the signals from your body route through your thalamus to your cerebral cortex, where you actually do your thinking, and all of your thoughts route through your thalamus before affecting other parts of your body.
Your hypothalamus sits right below the thalamus (hypo means below or beneath, just like hypothyroid means your thyroid is underactive). The hypothalamus is responsible for the body’s homeostasis, or balance with the outside world. It regulates a number of functions, including body temperature, thirst (and thus, fluid balance and blood pressure), hunger, sleep, sex drive, bonding, “fight or flight” responses to threats, and mood.
The hypothalamus is one of several structures included in what is considered the brain’s limbic system, considered to be the seat of emotions in the brain. Depression, whether organic or caused by an outside event, is associated with an overactive hypothalamus.