What is ACTH and why is it important?
ACTH, or adrenocorticotropic hormone, is a hormone produced by the pituitary gland, a small gland at the base of the brain. ACTH controls the production of another hormone called cortisol, which is made by the adrenal glands, two small glands located above the kidneys. Cortisol is widely known as the “stress hormone” because it helps the body cope with physical and emotional stress. However, cortisol also has many other functions in the body, such as regulating metabolism, inflammation, blood pressure, blood sugar and sleep cycle.
ACTH is part of a feedback system that involves the hypothalamus, the pituitary gland, the adrenal glands and certain hormones. This system is called the hypothalamic-pituitary-adrenal (HPA) axis. The hypothalamus is a part of the brain that controls many functions such as blood pressure, heart rate, body temperature and digestion. The hypothalamus sends signals to the pituitary gland to release ACTH when the body needs more cortisol. ACTH then stimulates the adrenal glands to produce cortisol and other hormones such as androgens (sex hormones) and adrenaline. When the cortisol level in the blood reaches a certain point, it signals back to the hypothalamus and the pituitary gland to stop producing ACTH. This way, the body maintains a balance of cortisol and other hormones.
ACTH levels can be measured by a blood test to check how well the HPA axis is working and to diagnose certain conditions that affect the adrenal glands or the pituitary gland. Abnormal ACTH levels can indicate either too much or too little cortisol production. Too much cortisol can cause Cushing’s syndrome, a condition that causes weight gain, high blood pressure, diabetes and other problems. Too little cortisol can cause Addison’s disease, a condition that causes fatigue, low blood pressure, low blood sugar and other problems. ACTH levels can also be affected by other factors such as stress, infection, pregnancy and medications.
What are the effects of cortisol on the body?
Cortisol has a wide range of effects on different organs and tissues in the body. Some of the main effects of cortisol are:
- Metabolism: Cortisol increases the breakdown of fats, proteins and carbohydrates to provide energy for the body. It also increases blood sugar levels by stimulating the liver to produce glucose and inhibiting the uptake of glucose by other cells. This helps the body cope with stress and maintain normal blood sugar levels.
- Inflammation: Cortisol suppresses the immune system and reduces inflammation by inhibiting the production and release of inflammatory mediators such as cytokines and prostaglandins. This helps prevent excessive tissue damage and promote healing.
- Blood pressure: Cortisol increases blood pressure by constricting the blood vessels and increasing the sensitivity of the heart to adrenaline. This helps the body maintain adequate blood flow to vital organs during stress.
- Sleep-wake cycle: Cortisol follows a circadian rhythm, meaning it has a daily pattern of secretion that is influenced by light and dark cycles. Cortisol levels are highest in the morning and lowest at night. This helps regulate the sleep-wake cycle and alertness.
Cortisol is essential for normal functioning of the body, but too much or too little cortisol can cause problems. High cortisol levels can result from chronic stress, pituitary tumors, adrenal tumors or steroid medications. High cortisol levels can cause Cushing syndrome, a condition that is characterized by weight gain, especially around the face and abdomen, thinning of the skin, bruising, muscle weakness, high blood pressure, diabetes, osteoporosis and mood changes. Low cortisol levels can result from autoimmune diseases, infections, genetic disorders or steroid withdrawal. Low cortisol levels can cause Addison disease, a condition that is characterized by fatigue, low blood pressure, low blood sugar, weight loss, nausea, vomiting, abdominal pain and skin darkening.