Regulation of Cortisol
Posted by Dr. James Wilson on Tue, Aug 25, 2009
The level of the adrenal stress hormone cortisol is a common measure of stress. Although cortisol is secreted by the zona fasciculate in the adrenal glands, it is regulated primarily from the brain.
Cortisol is responsible for many of the life sustaining functions attributed to the adrenal glands. The Hypothalamus/Pituitary/Adrenal Axis (HPA Axis) regulates the amount of cortisol circulating in your body at any particular time through a complex interaction between the hypothalamus (a regulatory part of the brain) the pituitary gland at the base of the brain and the adrenal glands. The regulatory trio operates through a negative feedback system and is referred to as the HPA Axis.
A negative feedback system works like the thermostat in a house or apartment. The thermostat senses the heat in the room and compares it with the desired temperature it has been set to. When the heat gets too low, the thermostat signals the relay switch to tell the furnace to ignite, sending hot air out into the room and raising the heat. When the heat has risen to the desired level, the thermostat signals the furnace off until more heat is needed.
In your body, your hypothalamus is analogous to the thermostat, your pituitary to the relay switch, your adrenals the furnace and your body is the room. The amount of cortisol that is released in comparable to the heat released from the furnace. To a large extent, you control the thermostat through the demands you place on your body. These demands arise from the physical and mental situations and your reactions to them.
No matter what the source of stress, most challenges to homeostasis (internal body balance) stimulate the HPA axis, resulting in increased secretion of cortisol. It is important to remember that all stresses are additive and cumulative. As stress increases, progressively higher levels of cortisol are required. Too much physical, emotional, environmental and/or psychological stress can deplete your adrenals, causing a decrease in the output of adrenal hormones, particularly cortisol. When higher levels of cortisol cannot be produced, as in adrenal fatigue, the person cannot fully or appropriately respond to stress.
Although it is impossible to exactly quantify the total stress load, your body does it every day, minute by minute, making instantaneous adjustments as these stresses change. It is when the body becomes unable to make the appropriate changes to these stresses that
adrenal fatigue begins. The more extreme the difference between the level of stress and the lack of cortisol, the more significant the consequences.