Adrenal Glands: Functions, Characteristics And Diseases

These glands are responsible for producing hormones that fulfill a series of fundamental functions.

Kidney glands

Our endocrine system is made up of a set of organs and tissues that are responsible for regulating vital functions for our body through the release of 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 such as cortisol, adrenaline or noradrenaline into the bloodstream.

In this article we explain what the adrenal glands are, what their structure is, what functions they perform in our body and what are the most common diseases and disorders related to a malfunction of these glands.

Adrenal glands: definition and structure

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

Each person has two adrenal glands, which can be divided into two parts: the outer portion, called the adrenal cortex; and the internal portion, which is called the adrenal medulla. The adrenal cortex is responsible for creating three different types of hormones: mineralocorticoids that conserve sodium in the body, glucocorticoids that increase blood glucose levels, and gonadocorticoids that regulate sex hormones like estrogen.

The adrenal cortex and adrenal medulla are enclosed in an adipose capsule that forms a protective layer around the adrenal gland. The adrenal cortex is essential for our survival; If it were to stop working properly, collapse and death would most likely occur, as it controls the basic metabolic processes for life.

For its part, the adrenal medulla, which is located within the adrenal cortex in the center of the gland, is in charge of secreting “stress hormones” such as adrenaline and norepinephrine. Let’s see in more detail what they consist of and what are the functions of these and other hormones produced in the adrenal glands.

Hormones of the adrenal glands

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 discussed earlier, some are vital for survival.

Both 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 zona fasciculata that 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 it can also decrease bone formation. This hormone also controls the sleep-wake cycle, and is released during times of stress to help the body get an energy boost and better handle an emergency situation.

The adrenal glands produce hormones in response to signals from the pituitary gland in the brain, which reacts to signals from the hypothalamus. This is known as the hypothalamic-pituitary-adrenal axis. For the adrenal gland to produce cortisol, the following occurs: First, the hypothalamus produces corticotropin-releasing hormone (CRH) that stimulates the pituitary gland to secrete adrenocorticotropic hormone (ACTH).

The hormone ACTH then stimulates the adrenal glands to produce and release cortisol into the blood (if there is too much or too little cortisol, these glands respectively change the amount of CRH and ACTH that is released, in what is known as a negative feedback loop. ). Excess cortisol production can occur from nodules in the adrenal gland or excess ACTH production from a tumor in the pituitary gland or other source.

2. Aldosterone

Aldosterone is a mineralocorticoid hormone produced by the zona glomerularis 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 the kidneys to absorb more sodium into the bloodstream and release potassium into 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 zone of the adrenal cortex, and are precursor hormones that are converted to female hormones (estrogens) in the ovaries and male hormones (androgens) in the testes.

However, the ovaries and testes produce estrogens and androgens in much greater amounts.

4. Adrenaline and noradrenaline

The adrenal medulla controls the hormones that initiate 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 the force of cardiac contractions, increase blood flow to the muscles and the brain, relax the smooth muscles of the airways and help the metabolism of glucose (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.

Features

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

It connects directly to the pituitary gland, which essentially picks up orders from the hypothalamus and sends signals to various organs and glands, including the adrenal glands, to carry out these orders.

A wide range of hormones, including estrogens, 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 central nervous system.

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

Another of the most important functions of the adrenal glands is the fight or flight response. When a person is stressed or scared, the adrenal gland releases a flood of hormones, such as adrenaline and cortisol, and these increase heart rate, raise blood pressure, increase energy supplies, sharpen concentration, and slow down other bodily processes so the body can escape or fight a threat.

However, an excessive response to stress can be counterproductive. Over-exposure to adrenal gland stress hormones can cause anxiety, depression, digestive problems, headaches, heart disease, trouble sleeping, weight gain, and impaired memory and concentration. The following are the most common disorders related to overproduction of adrenal hormones.

Related disorders

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

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

1. Adrenal insufficiency

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

Causes of primary adrenal insufficiency can include autoimmune disorders, fungal and other infections, cancer (rarely), and genetic factors. Although adrenal insufficiency usually develops over time, it can also appear suddenly as acute adrenal insufficiency (adrenal crisis). It has similar symptoms, but the consequences are more serious, including 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 make cortisol, aldosterone, or both. At the same time, they often experience an excess of androgens, which can lead to masculine characteristics in girls and precocious puberty in boys.

Congenital adrenal hyperplasia can remain 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 occurs due to excessive cortisol production in the adrenal glands.

Symptoms can include weight gain and fat deposits in certain areas of the body, such as the face, below the back of the neck (called a buffalo hump), and in the abdomen; thinning of arms and legs; purple stretch marks on the abdomen; facial hair; fatigue; muscular weakness; easily bruised skin; high blood pressure; diabetes; and other health problems.

Overproduction of cortisol can also be triggered by overproduction of adrenocorticotropic hormone (ACTH), by a benign tumor in the pituitary gland, 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 diseases.

4. Hyperaldosteronism

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

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

5. Pheochromocytoma

Pheochromocytoma is a tumor that produces excess production of adrenaline or norepinephrine in the adrenal medulla. Occasionally, neural crest tissue (a few-cell structure that transiently exists early in embryonic development), which has tissue similar to the adrenal medulla, may be the cause of overproduction of these hormones, resulting in known by the name of paraganglioma.

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

Bibliographic references:

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

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

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

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