Also called the suprarenal glands, the adrenal glands are important parts of the endocrine system. They produce a variety of hormones that play key roles in the stress response, metabolism and the balance of salt and water in the body. It is also an important member of an endocrine system axis consisting of the hypothalamus and pituitary gland.
Anatomy
The adrenal glands are located on the top of each of the kidneys in the abdominal cavity. They are triangular in shape and approximately 1.5 inches in height and 3 inches in length, according to endocrineweb.com. The adrenal glands are composed of two structures--the cortex and medulla--each of which performs different functions. The adrenal cortex is the outer layer and the adrenal medulla is the inner layer of the adrenal glands.
Adrenal Cortex
The adrenal cortex produces several hormones that play a vital role in the body's metabolism and physiological characteristics. Cortisol and corticosterone, two corticosteroids, and the hormone aldosterone are secreted from the adrenal cortex directly into the bloodstream. Cortisol serves an important role in controlling the metabolism and use of proteins, fats and carbohydrates, according to endocrineweb.com. Corticosterone, along with cortisol, plays a role in protecting the body from tissue damage by suppressing the inflammatory reaction of the immune system. Aldosterone functions in maintaining blood volume and blood pressure by inhibiting salt loss through the urine. Small amounts of sex hormones are also released by the adrenal cortex, but play only a minor role in sex characteristics.
Adrenal Medulla
The adrenal medulla provides an important function in helping the body handle emotional and physical stress. It secretes the hormones epinephrine and norepinephrine, which are sometimes referred to as adrenaline and noradrenaline, respectively. These hormones contribute to the body's "fight or flight" response by increasing blood pressure and blood flow, relaxing smooth muscles and increasing the body's energy supply by converting glycogen to glucose in the liver.
Disorders
A variety of conditions can affect hormone production by the adrenal glands, leading to a variety of symptoms and complications. Cushing's disease is a condition in which the adrenal cortex produces too much cortisol, which can damage body tissues. Addison's disease and congenital adrenal hyperplasia are two conditions in which too little cortisol--and aldosterone in Addison's disease--are secreted by the adrenal cortex. Addison's disease can be caused by an autoimmune reaction, cancer or infections, while congenital adrenal hyperplasia is a genetic disorder present at birth. Adrenal gland function may also be disrupted by tumors of the adrenal gland or pituitary gland, which controls the adrenal glands, according to the National Institute of Child Health and Human Development.
HPA Axis
The hypothalamic-pituitary-adrenal, or HPA, axis is a complex set of interactions and feedback loops between the hypothalamus, pituitary gland and adrenal glands. The primary communication flow of the HPA axis starts with the release of corticotrophin releasing factor (CRF) from the hypothalamus, which binds to the pituitary gland and stimulates the release of adrenocorticotropic hormone (ACTH) into the bloodstream. ACTH travels to and binds the adrenal glands, stimulating the release of cortisol into the bloodstream, where it acts on a variety of body processes. Cortisol completes the feedback loop by communicating with both the hypothalamus and pituitary, according to the Lundbeck Institute.
