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.