Adrenal glands: functions, features and diseases

Our endocrine system is made up of a collection of organs and tissues responsible for regulating the vital functions of our body by releasing different hormones.

Aspects as important for survival as the proper functioning of the metabolism or the immune system depend to a large extent on the adrenal glands, two small organs responsible for secreting hormones into the bloodstream such as cortisol, adrenaline or noradrenaline.

In this article we tell you what the adrenal glands are, What is its structure, what functions it performs in our body and what are the most common diseases and disorders linked to a dysfunction of these glands.

The adrenal glands: definition and structure

The adrenal glands are small triangular-shaped endocrine organs located at the top of both kidneys.. These glands are responsible for the production of hormones that help regulate metabolism, the immune system, blood pressure, the stress response, and other essential functions.

Every person has two adrenal glands, which can be divided into two parts: the outer part, called the adrenal cortex; and the inner part, which is called the adrenal medulla. The adrenal cortex is responsible for creating three different types of hormones: mineralocorticoids which retain sodium in the body, glucocorticoids which increase blood sugar levels, and gonadocorticoids which regulate sex hormones such as estrogen.

The adrenal cortex and adrenal medulla are enveloped in a fat capsule that forms a protective layer around the adrenal gland. The adrenal cortex is essential for our survival; if it stopped working, it is very likely that collapse and death would occur as it controls basic metabolic processes for life.

For its part, the adrenal medulla, located in the adrenal cortex at the center of the gland, is responsible for the secretion of “stress hormones” such as adrenaline and noradrenaline. Let’s see in more detail what they are and what are the functions of these and other hormones produced in the adrenal glands.

Adrenal gland hormones

The role of the adrenal glands in our body is to release certain hormones directly into the bloodstream.Many of which have to do with how the body responds to stress, and as we mentioned above, some are essential for survival.

The two parts of the adrenal glands, the adrenal cortex and the adrenal medulla, perform different and separate functions, and each area of ​​the adrenal cortex secretes a specific hormone. Let’s see below what are the key hormones produced by the adrenal cortex:

1. Cortisol

Cortisol is a glucocorticoid hormone produced by the fasciculated area which plays several important roles in the body.. Helps control the body’s use of fats, proteins and carbohydrates; suppresses inflammation; regulates blood pressure; increases blood sugar; and can also decrease bone formation. This hormone also controls the sleep and wake cycle and is released during times of stress to help the body gain energy and better manage an emergency.

The adrenal glands produce hormones in response to signals from the pituitary gland to the brain, which responds to signals from the hypothalamus. This is known as the hypothalamic-pituitary-adrenal axis. In order for the adrenal gland to produce cortisol, the following happens: First, the hypothalamus produces corticotropin releasing hormone (CRH) which stimulates the pituitary to secrete corticotropin (ACTH).

Then, the hormone ACTH stimulates the adrenal glands to produce and release cortisol in the blood (if there is too much or not enough cortisol, these glands respectively change the amount of CRH and ACTH that is released, in this is called a negative feedback circuit). Excess production of cortisol can come from nodules in the adrenal gland or from excessive ACTH production from a pituitary gland tumor or other source.

2. Aldosterone

Aldosterone is a mineralocorticoid hormone produced by the glomerular area of ​​the adrenal cortex. and plays a central role in the regulation of blood pressure and certain electrolytes (sodium and potassium).

This hormone sends signals to the kidneys, causing them to absorb more sodium into the bloodstream and release potassium in the urine. This means that aldosterone also helps regulate blood pH by controlling electrolyte levels in the blood.

3. DHEA and androgenic steroids

DHEA and androgenic steroids are produced by the reticular area of ​​the adrenal cortex, And are precursor hormones that convert the ovaries into female hormones (estrogen) and the testes into male hormones (androgens).

However, the ovaries and testes produce estrogen and androgens in much larger amounts.

4. Adrenaline and noradrenaline

The adrenal medulla controls the hormones that trigger the fight-or-flight response. The main hormones secreted by the adrenal medulla include epinephrine (adrenaline) and norepinephrine (norepinephrine), which have similar functions.

Among other functions, these hormones are able to increase the heart rate and strength of heart contractions, increase blood flow to muscles and the brain, relax smooth muscles in the airways, and aid glucose metabolism. (sugar).).

They also control the compression of blood vessels (vasoconstriction), which helps maintain blood pressure and increase it in response to stress. Like other hormones produced by the adrenal glands, adrenaline and norepinephrine are often activated in situations of physical and emotional stress when the body needs additional resources and energy to withstand unusual stress.

the functions

The adrenal glands are an integral part of the hypothalamic-pituitary-adrenal axis. The hypothalamus acts as the body’s thermostat and senses most of the important physiological elements involved in homeostasis, sending signals to correct for perceived harmful variations.

It connects directly to the pituitary gland, which essentially takes commands from the hypothalamus and sends signals to various organs and glands, including the adrenal glands, to carry out those commands.

A wide range of hormones, including estrogen, adrenaline, and cortisol, are produced by the adrenal glands. One of the main activities of cortisol is to increase the glucose available to the nervous system by breaking down proteins and fats into glucose in the liver, helping to block the absorption of glucose in other tissues besides the nervous system. central.

Cortisol also has potent anti-inflammatory and anti-allergic actions and decreases the activities of the immune system to reduce inflammatory conditions.

Another of the most important functions of the adrenal glands is the fight or flight response. When a person is stressed or frightened, the adrenal gland releases a torrent of hormones, Such as adrenaline and cortisol, and these increase heart rate, increase blood pressure, increase energy supplies, increase focus, and slow other bodily processes so that the body can escape or fight a threat.

However, an excessive stress response can be counterproductive. Excessive exposure to stress hormones from the adrenal glands can cause anxiety, depression, digestive problems, headaches, heart disease, sleep disturbances, weight gain and memory impairment and of concentration. The most common disorders related to the overproduction of adrenal hormones are described below.

related disorders

The two most common ways in which the adrenal glands cause health problems are by producing too much or too little of certain hormones, which leads to hormonal imbalances.

These adrenal abnormalities can be caused by various diseases of the adrenal glands or pituitary gland. Let’s look at the main disorders related to abnormal functioning of the adrenal glands.

1. Adrenal insufficiency

Adrenal insufficiency is a rare disease. It can be caused by disease of the adrenal glands (primary adrenal insufficiency or Addison’s disease) or by diseases of the hypothalamus or pituitary gland (secondary adrenal insufficiency). This condition is characterized by low levels of adrenal hormones and symptoms include: weight loss, loss of appetite, nausea and vomiting, fatigue, darkening of the skin (only in primary adrenal insufficiency) and abdominal pain, among others.

The causes of primary adrenal insufficiency can include autoimmune diseases, fungal and other infections, cancer (rarely), and genetic factors. Although adrenal insufficiency usually develops over time, it can also suddenly appear as acute adrenal insufficiency (adrenal crisis). He has similar symptoms, but the consequences are more serious and include life-threatening seizures and coma.

2. Congenital adrenal hyperplasia

Adrenal insufficiency can also be the result of a genetic disorder called congenital adrenal hyperplasia. Children born with this disease lack an essential enzyme needed to produce cortisol, aldosterone, or both. At the same time, they often suffer from an excess of androgens, which can lead to masculine characteristics in girls and precocious puberty in boys.

Congenital adrenal hyperplasia can go undiagnosed for years, depending on the severity of the enzyme deficiency. In more severe cases, babies can suffer from ambiguous genitalia, dehydration, vomiting, and lack of growth.

3. Cushing’s syndrome

Cushing’s syndrome is caused by excess production of cortisol in the adrenal glands.

Symptoms may include weight gain and fat deposits in certain areas of the body, such as the face, under the neck (called a buffalo hump) and in the abdomen; thinning of the arms and legs; purple streaks on the abdomen; Fur; tired; muscular weakness; easily massaged skin; arterial hypertension; Diabetes; and other health problems.

Excess production of cortisol can also be triggered by overproduction of corticotropin (ACTH), a benign pituitary tumor, or a tumor in another part of the body. This is known as Cushing’s disease. Another common cause of Cushing’s syndrome is the excessive and prolonged use of external steroids, such as prednisone or dexamethasone, which are prescribed to treat many autoimmune or inflammatory conditions.

4. hyperaldosteronism

Hyperaldosteronism is a disorder caused by an overproduction of aldosterone in one or both adrenal glands.

This causes an increase in blood pressure which often requires many medications to be able to be controlled. Some people can develop low levels of potassium in the blood, which can cause muscle pain, weakness, and spasms.

5. Pheochromocytoma

Pheochromocytoma is a tumor that produces excess production of adrenaline or norepinephrine in the adrenal medulla. Sometimes neural crest tissue (a structure of a few cells that is transiently there in the early stages of embryonic development), which has tissue similar to the adrenal medulla, can be the cause of the overproduction of these hormones, which the we call the paraganglioma.

Pheochromocytomas can cause persistent or sporadic high blood pressure which can be difficult to control with common medications. Other symptoms include: headache, sweating, tremors, anxiety, and rapid heartbeat. Some people are genetically predisposed to develop this type of tumor.

Bibliographical references:

  • Fardella, B. (2001). Congenital adrenal hyperplasia. Chilean Journal of Pediatrics, 72 (5), 408-415.

  • Rosol, TJ, Yarrington, JT, Latendresse, J. and Capen, CC (2001). Adrenal gland: structure, function and mechanisms of toxicity. Toxicological pathology, 29 (1), 41-48.

  • Tsigos, C. and Chrousos, GP (2002). Hypothalamic-pituitary-adrenal axis, neuroendocrine factors and stress. Journal of Psychosomatic Research, 53 (4), 865-871.

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