Hormones are messenger chemicals that travel through the bloodstream, communicating between the brain and the body to regulate systems or glands that need to be adjusted frequently. These glands may go out of balance when there are changes in the environment or the internal state of the individual. A feedback system between the glands and the brain acts to maintain the balance. Think of the operation of the thermostat on your furnace. When the temperature goes down, the thermostat signals the furnace to turn up the heat. When the house becomes too hot, the thermostat signals the furnace to stop producing heat. The thermostat is acting like the brain, and the signals are acting like hormones.
Several of these regulatory systems or glands can alter our emotions. The thyroid gland regulates our metabolism and is located in front of the throat. When the thyroid gland is too active, we call the illness hyperthyroidism. When the thyroid gland is underactive, we call that hypothyroidism. Depression can be a symptom of both illnesses.
The parathyroid is a very small gland that sits on the thyroid gland. This gland regulates calcium balance, which in turn regulates muscle firing. When this gland is overactive, the illness is called hyperparathyroidism. The person can experience depression as well as fatigue, nausea, vomiting, and excessive urination.
The adrenal glands, located on top of the kidneys, regulate our response to stress. In stressful situations, the level of cortisone, the hormone produced by the adrenal gland, increases. People with Addison’s disease produce too little cortisone and can develop depression. People with Cushing’s syndrome produce too much cortisone and can also develop depression. They also have an obese upper body, high blood pressure, and a round, red face. (Cushing’s syndrome can also occur when someone is given cortisone or steroids as medication.)
The gonadal glands regulate our reproductive functions. Depression can occur in women when there is an imbalance of the gonadal hormones.
The pancreas is a gland located behind the stomach that produces insulin, which regulates sugar metabolism. People who are diabetic produce too little insulin. Twenty-five per cent of people with diabetes develop depression. The direct cause is unknown.
The pituitary gland, located at the base of the brain, coordinates the feedback between all these glands and the brain. Interactions between the limbic system of the brain (which is concerned with automatic functions such as temperature and sleep regulation, as well as emotional reactions), the frontal lobe of the brain, and the pituitary gland can alter our emotions and cause depressive illness.