The Endocrine System and Glands of the Human Body

What Is the Endocrine System?

The endocrine system is a network of glands in your body that make the hormones that help cells talk to each other. They’re responsible for almost every cell, organ, and function in your body.

If your endocrine system isn't healthy, you might have problems developing during puberty, getting pregnant, or managing stress. You also might gain weight easily, have weak bones, or lack energy because too much sugar stays in your blood instead of moving into your cells where it's needed for energy.

What Is a Gland?

endocrine system illustrationA gland is an organ that makes and puts out hormones that do a specific job in your body. Endocrine glands release the substances they make into your bloodstream.

Endocrine System Functions

Your endocrine system:

  • Makes hormones that control your moods, growth and development, metabolism, organs, and reproduction
  • Controls how your hormones are released
  • Sends those hormones into your bloodstream so they can travel to other body parts

Parts of the Endocrine System

Many glands make up the endocrine system. The hypothalamus, pituitary gland, and pineal gland are in your brain. The thyroid and parathyroid glands are in your neck. The thymus is between your lungs, the adrenals are on top of your kidneys, and the pancreas is behind your stomach. Your ovaries (if you're a woman) or testes (if you're a man) are in your pelvic region.

  • Hypothalamus. This organ connects your endocrine system with your nervous system. Its main job is to tell your pituitary gland to start or stop making hormones.
  • Pituitary gland. This is your endocrine system’s master gland. It uses information it gets from your brain to tell other glands in your body what to do. It makes many important hormones, including growth hormone; prolactin, which helps breastfeeding moms make milk; and luteinizing hormone, which manages estrogen in women and testosterone in men.
  • Pineal gland. It makes a chemical called melatonin that helps your body get ready to go to sleep.
  • Thyroid gland. This gland makes thyroid hormone, which controls your metabolism. If this gland doesn't make enough (a condition called hypothyroidism), everything happens more slowly. Your heart rate might slow down. You could get constipated. And you might gain weight. If it makes too much (hyperthyroidism), everything speeds up. Your heart might race. You could have diarrhea. And you might lose weight without trying.
  • Parathyroid. This is a set of four small glands behind your thyroid. They play a role in bone health. The glands control your levels of calcium and phosphorus.
  • Thymus. This gland makes white blood cells called T-lymphocytes that fight infection and are crucial as a child's immune system develops. The thymus starts to shrink after puberty.
  • Adrenals. Best known for making the "fight or flight" hormone adrenaline (also called epinephrine), these two glands also make hormones called corticosteroids. They affect your metabolism and sexual function, among other things.
  • Pancreas. This organ is part of both your digestive and endocrine systems. It makes digestive enzymes that break down food. It also makes the hormones insulin and glucagon. These ensure you have the right amount of sugar in your bloodstream and your cells.
  • If you don't make insulin, which is the case for people with type 1 diabetes, your blood sugar levels can get dangerously high. In type 2 diabetes, the pancreas usually makes some insulin but not enough.
  • Ovaries. In women, these organs make estrogen and progesterone. These hormones help develop breasts at puberty, regulate the menstrual cycle, and support a pregnancy.
  • Testes. In men, the testes make testosterone. It helps them grow facial and body hair at puberty. It also tells the penis to grow larger and plays a role in making sperm.

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Health Issues

As you get older, it's natural to notice some things related to your endocrine system. Your metabolism tends to slow down. So you might gain weight even though you haven't changed how you eat or exercise. Hormonal shifts also explain, at least in part, why you're more likely to have heart disease, osteoporosis, and type 2 diabetes as you age.

No matter how old you are, stress, infections, and being around certain chemicals can also mess with parts of your endocrine system. And genetics or lifestyle habits can increase your chances of an endocrine disorder like hypothyroidism, diabetes, or osteoporosis.

Endocrine System Disorders

  • Acromegaly. Sometimes the pituitary gland makes too much growth hormone and your bones get bigger. It usually affects your hands, feet, and face. It usually starts in middle age.
  • Adrenal insufficiency. When you have this, your adrenal glands don’t make enough of certain hormones, like cortisol, which controls stress.
  • Cushing's disease. In this, your body makes too much cortisol. You could gain weight, get stretch marks, bruise easily at first, then get weakened muscles and bones and possibly develop a hump on your upper back.
  • Hyperthyroidism. This is when your thyroid gland makes more hormones than your body needs. You might hear it called overactive thyroid. It makes your system run fast and you might feel nervous, lose weight, and have a rapid heartbeat or trouble sleeping.
  • Hypothyroidism. When your body doesn’t make enough thyroid hormone, your system slows down. You might feel tired, gain weight, have a slow heartbeat, and get joint and muscle pains.
  • Hypopituitarism. Sometimes your pituitary gland doesn’t make enough of certain hormones and your adrenal and thyroid glands can’t work right.
  • Multiple endocrine neoplasia. This is a group of disorders that affect your endocrine system. It causes tumors on at least two endocrine glands or in other organs and tissues.
  • Polycystic ovary syndrome. An imbalance of reproductive hormones can cause your ovaries to either not make an egg or not release it during ovulation. This can throw off your periods, cause acne, and make hair to grow on your face or chin.
  • Precocious puberty . When glands that control reproduction don’t work properly, some kids start puberty abnormally early -- around 8 in girls and 9 in boys.
WebMD Medical Reference Reviewed by Michael Dansinger, MD on June 02, 2019

Sources

SOURCES:

American Diabetes Association: "Facts About Type 2."

Endocrine Awareness Center for Health: "The Thymus Glands."

Hormone Health Network: "Endocrine Glands and Types of Hormones," "Factors that Affect Endocrine Function," "Journey Through the Endocrine System," "What Does the Thyroid  Gland Do?"

KidsHealth.org: "Endocrine System."

Mayo Clinic: "Type 1 Diabetes."

Washington University in St. Louis School of Medicine: "Endocrine and Metabolic Disorders."

KidsHealth: “Endocrine System.”

You and Your Hormones: “Glands.”

Mayo Clinic: “Acromegaly.”

National Institute of Diabetes and Digestive and Kidney Diseases: “Adrenal Insufficiency & Addison’s Disease,” “Hyperthyroidism (Overactive Thyroid),” “Hypothyroidism (Underactive Thyroid).”

Genetics Home Reference: “Cushing disease,” “Multiple endocrine neoplasia.”

Hormone Health Network: “Hypopituitarism.”

Office on Women's Health: “Polycystic ovary syndrome.”

National Organization for Rare Disorders: “Precocious Puberty.”

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