A pair of glands located one above each kidney in the central abdomen. They are sometimes called the suprarenal (above the kidneys) glands. The adrenal glands are part of the body’s endocrine system, a network of structures that produce hormones (chemicals secreted directly into the bloodstream). Each adrenal gland is actually two distinct structures, the adrenal cortex and the adrenal medulla.
The adrenal cortex is the outer portion of the adrenal gland’s structure and wraps around the adrenal medulla. The adrenal cortex is key to the body’s metabolic functions. The hormones it produces, called corticosteroids, include
• Aldosterone, which regulates blood pressure and blood volume by controlling the amount of sodium that the kidneys filter from the blood.
• cortisol, which regulates the way the body metabolizes energy (uses fats, carbohydrates, and proteins) and suppresses inflammation. cortisol plays a key role in immune functions and also is known as the body’s stress hormone; the adrenal cortex releases more cortisol when the body experiences stress.
• Small amounts of androgen, the male sex hormone (in men and women alike).
The adrenal medulla, which lies within the adrenal cortex, is actually made of nerve tissue. it produces epinephrine and norepinephrine. These hormones have numerous functions within the body, particularly in the cardiovascular system. They affect the constriction and relaxation of smooth muscle tissue in the arteries and veins, the force and rate of the heartbeat, and blood pressure. Because other tissues in the body produce these hormones, the adrenal medulla is considered nonessential for life: That is, it is possible to live without the functions it fulfills and experience no life-threatening complications as a result.
Adrenal Medulla and Parkinson’s Disease
The adrenal medulla has no direct correlation to Parkinson’s disease. However, because the brain produces epinephrine and norepinephrine, it has drawn the attention of researchers as a potential source for replacing these substances in the brain through allograft. The adrenal medulla produces and releases epinephrine and norepinephrine into the blood. This makes them hormones. When the neurons in the brain produce and release epineph-rine and norepinephrine during synapses, these substances are considered neurotransmitters. They are catecholamines, the same chemical family to which dopamine belongs. chemically, these substances are identical wherever in the body they are produced. in the body, some norepinephrine converts to dopamine that body systems other than the brain, such as the cardiovascular system, use. This dopamine cannot cross the blood-brain barrier, however, so it cannot affect the brain. But what if there was a way to circumvent the blood-brain barrier? The prospect intrigued researchers studying Parkinson’s disease, arousing speculation that adrenal medulla cells, if transplanted into the brain of a person with Parkinson’s disease, might be able to replace dying substantia nigra cells and continue to provide the brain with an adequate supply of dopamine. Although this is a solution that seems sound on its surface, so far adrenal medullary transplant has not succeeded as a treatment for Parkinson’s disease.