An adrenal gland is found on the upper edge of each kidney, where it is attached to the kidney. Composed of two parts, the inner part of the gland is called the adrenal medulla. The outer part is the adrenal cortex. There are three areas, or zones, within the cortex. Each zone has the responsibility of making and releasing a particular hormone.
Making Mineralocorticoids
Mineralocorticoids are steroid hormones that have the responsibility of affecting the metabolism of sodium and potassium. According to Kim Barrett, Ph.D., writing in "Ganong's Review of Medical Physiology," aldosterone is the only mineralocorticoid that is secreted in significant amounts by the adrenal cortex. Aldosterone is made from cholesterol in the area of the adrenal cortex called the zona glomerulosa. It tells the kidneys to hold onto sodium and release potassium. It is important for increasing the volume of blood and blood pressure. When the kidneys hold onto sodium, more water is reabsorbed. This increases the volume of blood, which makes the blood pressure go up. Addison's disease is a disorder where the adrenal cortex is destroyed. In people with Addison's, the adrenal glands do not make and secrete enough aldosterone. They feel very weak because they have hyponatremia, or low levels of sodium in the bloodstream. Conn's syndrome is a disease in which too much aldosterone is released. People with Conn's have hypernatremia, or high levels of sodium in the blood, and hypertension.
Making Glucocorticoids
Glucocorticoids are steroid hormones which, like mineralocorticoids, are made from cholesterol. But glucocorticoids are made in the part of the adrenal cortex called the zona fasciculata. The main ones secreted by the adrenal gland are cortisol, also called hydrocortisone, and corticosterone. These hormones have several important functions. They make the liver make glucose and glycogen faster. Glycogen is the stored form of glucose; it is reserve energy for the body. The hormones make adipose, or fat, tissue release lipids and fatty acids into the bloodstream. They make the skeletal muscle release amino acids--proteins--into the blood. The hormones are anti-inflammatory; they decrease the activities of the cells that are part of the inflammatory response. This will decrease any irritation and swelling. In Addison's disease, the adrenal glands cannot release enough aldosterone or glucocorticoids. This is an additional reason why people are weak, because they have hypoglycemia, or low levels of glucose in their bloodstream. Hypercortisolism, or high levels of cortisol in the blood, causes Cushing's syndrome, as explained by Tobias Else, M.D., in "Pathophysiology of Disease."
Making Androgens
The adrenal gland makes androgens from cholesterol in the zona reticularis. As Dr. Barrett writes in "Ganong's Review of Medical Physiology," the main androgens that are made are called androstenedione and dehydroepiandrosterone, or DHEA.
References
- "Ganong's Review of Medical Physiology"; Kim Barrett, Ph.D., Susan Barman, Ph.D. et al.; 2010
- "Pathophysiology of Disease: An Introduction to Clinical Medicine"; Stephen McPhee, M.D., Gary Hammer, M.D., Ph.D.; 2010
