Cortisol is a hormone produced by the adrenal glands. Production and secretion of cortisol is stimulated by ACTH (adrenocorticotropic hormone), a hormone produced by the pituitary gland – a tiny organ located inside the head below the brain. Cortisol has a range of roles in the body. It helps break down protein, glucose, and lipids, maintain blood pressure, and regulate the immune system. Heat, cold, infection, trauma, stress, exercise, obesity, and debilitating disease can influence cortisol concentrations. The hormone is secreted in a daily pattern, rising in the early morning, peaking around 8 am, and declining in the evening. This pattern, which is sometimes called the “diurnal variation” or “circadian rhythm,” changes if you work irregular shifts (such as the night shift) and sleep at different times of the day.

Inadequate amounts of cortisol can cause nonspecific symptoms such as weight loss, muscle weakness, fatigue, low blood pressure, and abdominal pain. Sometimes decreased production combined with a stressor can cause an adrenal crisis that requires immediate medical attention.

Too much cortisol can cause increased blood pressure, high blood sugar, obesity, fragile skin, purple streaks on the abdomen, muscle weakness, and osteoporosis. Women may have irregular menstrual periods and increased facial hair; children may have delayed development and a short stature.