Cortisol is a steroid hormone produced in the cortex of adrenal gland. It belongs to a class of hormones called glucocorticoids and plays an important role in regulating cardiovascular function, blood pressure, glucose metabolism, sugar maintenance, and inflammatory response. Cortisol is best known as the stress hormone. It is released in response to stress, and is part of the fight or flight system.
Under normal conditions the body regulates cortisol levels which are usually high in the morning and low at night. But under stressful conditions more cortisol is secreted. Small increases in cortisol produce positive effects such as increased sustained energy, diminished pain sensitivity or memory enhancement. But a prolonged cortisol increase during chronic stress results in negative side effects: increased blood pressure, sugar imbalance in blood, decreased bone density, cognitive problems, and reduced thyroid function. It also slows down healing processes and suppresses the immune system, perhaps the reason we are more apt to get sick when we are stressed.
Continuously, stress-induced elevated cortisol levels lead to an increase in the level of other hormones (testosterone, estradiol, insulin). High cortisol levels are often linked to insulin resistance (Type 2 Diabetes), weight gain and general inflammatory conditions. High cortisol is toxic to the brain and can cause memory loss and contribute to Alzheimer’s disease or senile dementia. Elevated cortisol levels and lack of diurnal variation have been identified with Cushing’s disease. Low cortisol levels are found in primary adrenal insufficiency (e.g. adrenal hypoplasia, Addison’s disease).
Cortisol and progesterone bind to common receptors in cells. Cortisol blocks progesterone activity, and some suggest, that high levels of cortisol, initiated by chronic stress, dispose one to a condition called estrogen dominance. Estrogen dominance is condition where women cease to ovulate regularly and progesterone concentrations are lower than necessary during the second half of the menstrual cycle. Many suspect estrogen dominance underlies PMS and other cycle related symptoms.