The Anatomy of the Adrenal Gland

Produces hormones for metabolism, the immune system, and more.

In This Article
Table of Contents

The adrenal glands (also known as suprarenal glands) release certain hormones that help our body function. They impact everything from regulating metabolism, helping the immune system, managing stress responses in the body and more. Sometimes the adrenal glands can produce too little or too much of these hormones, leading to adrenal disorders like Cushing’s syndrome or Addison’s disease. The most important job of the adrenal glands is to help keep the body in balance from head to toe. They do this by making sure the amount of hormones available to help both internal and external bodily processes is stable.

Anatomy

The adrenal glands are two small, triangular-shaped glands that sit directly on top of the kidneys. The two major parts of the adrenal gland are the cortex and the medulla. The gland is held together by an adipose capsule, which acts as a protective barrier.

The cortex is the outer layer and is the largest part of the adrenal gland. It is divided into three zones—zona glomerulosa, zona fasciculata, and zona reticularis—all of which are responsible for producing different hormones. The zona glomerulosa is responsible for aldosterone (which regulates blood pressure), the zona fasciculata produces cortisol (used for stress and metabolism), and the zona reticularis produces sex hormones testosterone and estrogen.

The medulla is the inner layer of the adrenal gland that makes a group of hormones called catecholamines. These are referred to as “fight or flight” hormones that help you respond to stress. One of the biggest hormones in this category is adrenaline.

Anatomical Variations

In certain cases, there may be variations in the adrenal arteries, the arteries in the stomach that are responsible for supplying blood to the adrenal glands. Typically the adrenal gland has input from three arteries on both the left side and right side. Past research has found that this isn’t always the case, as some individuals may have only four to five total artery inputs, or sometimes even less.

Variations of adrenal veins appear to be relatively common, having been found in 13% of cases of people undergoing removal of the adrenal gland. This can have significance during surgery. Normally, one central vein drains each adrenal gland, yet there are many variations.

Function

The adrenal glands release hormones directly into the bloodstream. Together with the thyroid gland, the two make up the body's endocrine system. Hormones produced by these glands regulate growth, the physical and chemical process of the metabolism, as well as sexual development and function. They do this by carrying specific hormones in the bloodstream directly to the areas and organs of the body that need it to function optimally.

Adrenal glands are able to produce cortisol (one of the major hormones needed for several body mechanisms like your metabolism, reducing inflammation, and even improving memory) due to signals they get from the pituitary gland (a pea-sized gland located in the brain just behind the bride of the nose) as well as the hypothalamus (a small region near the base of the brain close to the pituitary gland). This interaction is often referred to as the hypothalamic–pituitary–adrenal axis (HPA axis)

For example, the hypothalamus will release a hormone called corticotropin-releasing hormone (CRH), and this tells the pituitary gland to secrete a separate hormone called adrenocorticotropic hormone (ACTH). ACTH is what stimulates the adrenal glands to make and release cortisol into the bloodstream. This process is repeated whenever necessary, as the hypothalamus and pituitary gland together are able to tell how much cortisol is in the blood and whether or not more is needed.

Other hormones produced by the adrenal glands handle important mechanisms in the body. Aldosterone, produced in the zona glomerulosa part of the cortex, sends signals to the kidneys to absorb sodium and release potassium through urine, regulating both blood pressure and the number of electrolytes in the body.

Adrenaline and noradrenaline hormones are secreted by the adrenal medulla and have effects such as increasing the heart rate, controlling blood flow throughout the body, and vasoconstriction (the constriction of blood vessels that can affect blood pressure).

Associated Conditions

The most common conditions associated with adrenal glands happen when too much or too little hormones are produced. Adrenal glands can also be impaired if there’s a disorder in the pituitary gland, as it signals to the adrenal gland when to make certain hormones like cortisol and aldosterone. Adrenal gland disorders include:

Tests

There are several tests your healthcare provider can do to assess adrenal gland function, typically through blood and/or urine samples. Some frequent tests of the adrenal glands include:

  • 17-Hydroxyprogesterone (or 17-OHP) test: This test is usually done as part of newborn screening in order to detect congenital adrenal hyperplasia. A heel prick blood sample is analyzed for 17-hydroxyprogesterone, which is created when cortisol is produced by the adrenal glands.
  • Aldosterone test: Done through both blood or urine, this test monitors how much aldosterone is in the body, which is one of the hormones that regulates blood pressure. An aldosterone test can diagnose adrenal fatigue or insufficiency, or a possible tumor in the adrenal glands. Benign adrenal gland tumors are very common, while adrenal cancer is more rare, affecting 1 or 3 per 1 million people.
  • Cortisol test: This test is used to pinpoint Cushing’s syndrome and Addison’s disease (when the adrenal glands make too much and too little cortisol, respectively). A blood draw is done twice during the day, once in the morning and another later in the day. Cortisol can also be measured with a 24-hour urine test (where you collect a day’s worth of urine and send it to a laboratory for analysis) or through saliva as a swab test (in certain instances).
  • Dehydroepiandrosterone sulfate (DHEAS) test: DHEAS can be converted into sex hormones like estrogen and testosterone. A DHEAS blood test is done to diagnosis adrenal tumors or cancer, or any sex hormone imbalances that may be affecting a person's development. In females, an imbalance may result in amenorrhea, hirsutism, or infertility, and in males there may be or early puberty.
Was this page helpful?
Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Johns Hopkins Medicine. Adrenal glands.

  2. Manso JC, Didio LJ. Anatomical variations of the human suprarenal arteries. Ann. Anat. 2000;182(5):483-8. doi:10.1016/S0940-9602(00)80064-3

  3. Scholten A, Cisco RM, Vriens MR, Shen WT, Duh QY. Variant adrenal venous anatomy in 546 laparoscopic adrenalectomies. JAMA Surg. 2013;148(4):378-83. doi10.1001/jamasurg.2013.610

  4. Cesmebasi A, Du plessis M, Iannatuono M, Shah S, Tubbs RS, Loukas M. A review of the anatomy and clinical significance of adrenal veins. Clin Anat. 2014;27(8):1253-63. doi:10.1002/ca.22374

  5. American Association for Clinical Chemistry. 17-Hydroxyprogesterone. Updated October 7, 2019.

  6. Urology Care Foundation. Getting to know the adrenal glands.

  7. American Association for Clinical Chemistry. Cortisol. Updated March 6, 2020.

  8. American Association for Clinical Chemistry. DHEAS test. Updated January 31, 2020.