The adrenal glands are a significant part of human endocrine system, which is an intricate network of glands that produce interacting hormones. Those hormones are responsible for regulating a plethora of body functions, and can even affect other endocrine organs. For example,  the adrenal glands are influenced by hormones that are produced by the hypophysis and the hypothalamus in the central nervous system.

In the body, there are two adrenal glands, one at the top of each kidney in the retroperitoneal area, held in the position by vascular attachments and fibrous bands. Their main function is to produce hormones: the outer layer (also known as the adrenal cortex) produces the corticosteroids cortisol, aldosterone, and androgens (or male sex hormones), while the inner layer (also known as the adrenal medulla) produces epinephrine and norepinephrine.

Adrenal glands sit atop the kidneys and are composed of an outer cortex and an inner medulla, which produce different types of hormones. Human endocrine system - Image Copyright: Designua / Shutterstock

Cortisol has an indispensable role in the metabolism of proteins, carbohydrates, and lipids, preserving the adequate functioning of the immune system, but it also helps the body to cope with stress. Aldosterone aids in the regulation of sodium and potassium levels, whereas androgens influence the development of secondary sexual characteristics. On the other hand, epinephrine and norepinephrine play a pivotal role in the organism’s immediate reaction to stress.

Causes and Main Types of Adrenal Disorders

Among the main causes of adrenal disorders are benign tumors known as adrenal adenomas. They arise due to presumptive genetic mutations and can occur at any age, although they are more frequently observed in older individuals. Symptoms are usually caused by the growing tumor pressing on surrounding organs, but also affecting the normal production of adrenal hormones. If the tumor itself hyper-produces hormones, it is usually known as functioning tumor.

Overproduction of cortisol is an established condition known as Cushing’s syndrome that stems from the aforementioned functioning tumor, but also from overstimulation of the adrenal gland from excess pituitary hormones. This condition can also develop due to the long-term treatment with corticosteroid medication such as prednisone.
 

Similar conditions are hyperaldosteronism that is caused by overproduction of aldosterone (most often by a functioning tumor), virilization caused by the overproduction of adrenal androgens, as well as pheochromocytomas caused by the functioning tumors of the adrenal medulla that produce excess quantities of epinephrine and norepinephrine.

On the other hand, insufficient production of the adrenal hormones is known as primary or secondary adrenal insufficiency. Adrenal insufficiency in which the adrenal cortex produces inadequate amounts of corticosteroids is known as Addison’s disease, and it is caused by an autoimmune disorder, by infections (mostly tuberculosis) or by metastatic cancers. Sudden halt in the administration of corticosteroid medications can result in a rapid fall in the body’s natural level of corticosteroids and provoke potentially lethal Addisonian crisis.

Dominant Symptoms and Signs

Even though a majority of adrenal adenomas do not present with any symptoms, their growth may press other organs and result in abdominal pain and weight loss. Symptoms are also noticeable when hormone production is affected – either due to a functioning tumor or other causes.

Cushing’s syndrome manifests with weight gain around the chest and abdomen, stretch marks, acne, facial changes such as moon face, excessive hair growth, deposits of fat between the shoulder blades, muscle weakness, hypertension, and diabetes mellitus. The most distinguishing features that help to differentiate Cushing’s syndrome from simple obesity are signs of protein catabolism.

Hyperaldosteronism is characterized by high blood pressure with headaches and facial flushing, low levels of potassium that result in constipation and weakness, suppressed plasma-renin activity and increased aldosterone excretion. As already mentioned, the overproduction of adrenal androgens results in exaggerated secondary male sexual characteristics, whereas overproduction of epinephrine and norepinephrine leads to hypertension, excessive sweating, palpitations, and headaches.

Adrenal insufficiency usually manifests with fatigue, weakness, thirst, anorexia, salt cravings, low blood pressure, postural dizziness, and occasional salt cravings, but the disease is usually diagnosed after a significant illness or stress that unmasks cortisol and mineralocorticoid deficiency in an alarming and hazardous adrenal crisis.

How to Diagnose and Treat Adrenal Disorders?

Most adrenal disorders are diagnosed based on medical history and clinical presentation; in addition, a vast majority of adrenal adenomas are incidental findings on scans pursued for other reasons. Nevertheless, blood and urine tests that measure the levels of hormones (but also sodium and potassium), as well as imaging techniques such as computed tomography (CT) or magnetic resonance imaging (MRI) can aid in establishing a correct diagnosis.

The treatment primarily depends on the specific underlying disorder. For example, small and nonfunctioning adrenal adenomas usually necessitate only regular follow-up, whereas large and functional tumors may need a surgical approach to remove the tumor (or even the entire adrenal gland).

Therapy for adrenal overproduction usually includes medications that block hormone synthesis. If the underlying cause of overproduction is found in hypophysis or hypothalamus, the treatment is then directed primarily at the underlying cause. Adrenal insufficiency can be adequately treated with hormone replacement medications, although adrenal crisis requires urgent hospitalization and administration of fluids, glucose, and corticosteroid injections.