What are hormones?

Hormones are chemicals that coordinate different functions in your body by carrying messages through your blood to your organs, skin, muscles and other tissues. These signals tell your body what to do and when to do it. Hormones are essential for life and your health.

Scientists have identified over 50 hormones in the human body so far.

Hormones and most of the tissues (mainly glands) that create and release them make up your endocrine system. Hormones control many different bodily processes, including:

  • Metabolism.
  • Homeostasis (constant internal balance), such as blood pressure and blood sugar regulation, fluid (water) and electrolyte balance and body temperature.
  • Growth and development.
  • Sexual function.
  • Reproduction.
  • Sleep-wake cycle.
  • Mood.

With hormones, a little bit goes a long way. Because of this, minor changes in levels can cause significant changes to your body and lead to certain conditions that require medical treatment.

What do hormones do?

Hormones are chemical messengers that affect and manage hundreds of bodily processes. Often, a bodily process involves a chain reaction of several different hormones.

A hormone will only act on a part of your body if it “fits” — if the cells in the target tissue have receptors that receive the message of the hormone. Think of a hormone as a key and the cells of its target tissue, such as an organ or fat tissue, as specially shaped locks. If the hormone fits the lock (receptor) on the cell wall, then it’ll work; the hormone will deliver a message that causes the target site to take a specific action.

Your body uses hormones for two types of communication. The first type is communication between two endocrine glands: One gland releases a hormone, which stimulates another gland to change the levels of hormones that it’s releasing. An example of this is the communication between your pituitary gland and thyroid. Your pituitary gland releases thyroid-stimulating hormone (TSH), which triggers your thyroid gland to release its hormones, which then affect various aspects of your body.

The second type of communication is between an endocrine gland and a target organ. An example of this is when your pancreas releases insulin, which then acts on your muscles and liver to help process glucose.

Which body tissues make hormones?

Specialized glands that make up your endocrine system make and release most of the hormones in your body. A gland is an organ that makes one or more substances, such as hormones, digestive juices, sweat or tears. Endocrine glands release hormones directly into your bloodstream.

Your endocrine system consists of the following glands:

  • Hypothalamus.
  • Pituitary gland.
  • Pineal gland.
  • Thyroid.
  • Parathyroid glands.
  • Adrenal glands.
  • Pancreas.
  • Ovaries.
  • Testes.

But not all organs and tissues that release hormones or hormone-like substances are considered part of the endocrine system. Other body tissues that release hormones include:

  • Adipose tissue (fat tissue).
  • Kidneys.
  • Liver.
  • Gut (gastrointestinal tract).
  • Placenta.

Hypothalamus

Your hypothalamus is a small region of your brain that connects to your pituitary gland through the pituitary stalk. It releases several hormones that control your pituitary gland.

Your hypothalamus makes the following hormones:

  • Corticotrophin-releasing hormone.
  • Dopamine.
  • Gonadotrophin-releasing hormone.
  • Growth hormone-releasing hormone.
  • Oxytocin (your hypothalamus makes oxytocin, but your pituitary gland stores and releases it).
  • Somatostatin.
  • Thyrotropin-releasing hormone.

Pituitary gland

Your pituitary gland is a pea-sized gland at the base of your brain, behind the bridge of your nose and directly below your hypothalamus. It consists of two lobes: the posterior lobe and the anterior lobe. Your pituitary gland releases several hormones — many of which control the functions of other endocrine glands.

The anterior pituitary makes and releases the following six hormones:

  • Adrenocorticotropic hormone (ACTH or corticotropin).
  • Follicle-stimulating hormone (FSH).
  • Growth hormone (GH).
  • Luteinizing hormone (LH).
  • Prolactin.
  • Thyroid-stimulating hormone (TSH).

The posterior pituitary releases the following hormones:

  • Antidiuretic hormone (ADH, or vasopressin).
  • Oxytocin.

Pineal gland

Your pineal gland is a tiny gland in your brain that’s located beneath the back part of the corpus callosum (nerve fibers that connect the two parts of your brain). It releases the hormone melatonin, which helps control your sleep-wake cycle.

Thyroid gland

Your thyroid is a small, butterfly-shaped gland located at the front of your neck under your skin. Your thyroid’s main job is to control the speed of your metabolism (metabolic rate), which is the process of how your body transforms the food you consume into energy.

Your thyroid releases the following hormones:

  • Thyroxine (T4).
  • Triiodothyronine (T3).
  • Reverse triiodothyronine (RT3).
  • Calcitonin.

Thyroxine and triiodothyronine are often collectively called “thyroid hormone.”

Parathyroid glands

Most people have four pea-sized parathyroid glands located behind their thyroid gland (the butterfly-shaped gland in your neck). Sometimes, your parathyroid glands are located along your esophagus or in your chest. These are known as ectopic (in an abnormal place) parathyroid glands.

The main job of your parathyroid glands is to release parathyroid hormone (PTH), which is responsible for the calcium balance in your blood and bone health.

Adrenal glands

Your adrenal glands, also known as suprarenal glands, are small, triangle-shaped glands that are located on top of each of your two kidneys.

Your adrenal glands make the following hormones:

  • Cortisol.
  • Aldosterone.
  • DHEA and androgens.
  • Adrenaline (epinephrine).
  • Noradrenaline (norepinephrine).

Pancreas

Your pancreas is an organ in the back of your abdomen (belly). It’s part of your digestive system and endocrine system.

The islet cells (endocrine cells) in your pancreas make the following hormones:

Ovaries

People assigned female at birth (AFAB) have two ovaries — each located on both sides of their uterus below the opening of the fallopian tubes. In addition to containing the egg cells necessary for reproduction, the ovaries produce the following hormones:

Testes

People assigned male at birth (AMAB) have two testes that hang in a pouch outside of their body below their penis. The testes are part of the male reproductive system and produce sperm and the hormone testosterone.

Adipose tissue (fat tissue)

Adipose tissue is commonly known as body fat. It’s located all over your body, including under your skin, around internal organs, between muscles, in bone marrow and breast tissue.

Adipose tissue makes and releases the following hormones:

  • Leptin.
  • Adiponectin.
  • Plasminogen activator inhibitor-1.
  • Estrogen.
  • Angiotensin.

Kidneys

Your kidneys are two bean-shaped organs that filter your blood. They’re part of your urinary system, but they also produce hormones, including:

  • Erythropoietin.
  • Renin.
  • The active form of vitamin D (vitamin D isn’t actually a vitamin — it’s a prohormone, which is a substance that your body converts into a hormone).

Liver

Your liver is an essential organ and gland, performing hundreds of functions necessary to sustain life. It’s considered part of your digestive system, but also produces hormones, including:

  • Insulin-like growth factor 1 (IGF-1).
  • Angiotensinogen.

Gut (gastrointestinal tract)

Your gut (gastrointestinal tract) is the long, connected tube that starts at your mouth and ends at your anus. It’s responsible for digestion. Scientists are currently studying the hormones that your gut makes and their effects. These hormones include:

  • Ghrelin.
  • Somatostatin.
  • Glucagon-like peptide 1 (GLP-1).

Placenta

The placenta is a temporary organ that develops in your uterus during pregnancy. It provides oxygen and nutrients to your unborn baby. The placenta produces the hormones estrogen and progesterone to maintain the pregnancy.

What conditions are caused by hormone issues?

Dozens of medical conditions are caused by hormone issues. For most hormones, having too much or too little of them causes symptoms and issues with your health. These imbalances often require treatment. Some of the most common hormone-related conditions include:

What causes hormonal imbalances?

Each hormone-related condition can have several different possible causes. In general, the main conditions or situations that cause hormone imbalances include:

  • Tumors, adenomas or other growths.
  • Damage or injury to an endocrine gland.
  • Autoimmune conditions.
  • Hereditary gene mutations (changes) that cause problems with the structure and/or function of an endocrine gland.

Primary healthcare providers can diagnose and help you manage many hormone conditions. However, you may benefit from seeing an endocrinologist.

An endocrinologist is a healthcare provider who specializes in endocrinology, a field of medicine that studies conditions related to your hormones. An endocrinologist can diagnose endocrine (hormone) conditions, develop treatment and management plans for them and prescribe medication.

A note from Cleveland Clinic

Hormones are an important and essential part of human existence. While your body normally carefully balances its hormones, having too little or too much of a certain hormone can lead to health problems. If you’re experiencing any concerning symptoms, it’s important to talk to your healthcare provider. They can order tests to see if you have a hormone imbalance or if something else is causing your symptoms.

Last reviewed by a Cleveland Clinic medical professional on 02/23/2022.

References

  • Better Health Channel. Hormonal (Endocrine) System. (https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/hormonal-endocrine-system) Accessed 2/23/2022.
  • McLaughlin MB, Jialal I. Biochemistry, Hormones. (https://www.ncbi.nlm.nih.gov/books/NBK541112/) [Updated 2021 Jul 22]. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2021 Jan-. Accessed 2/23/2022.
  • Merck Manual: Consumer Version: Endocrine Glands. (https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/biology-of-the-endocrine-system/endocrine-glands) Accessed 2/23/2022.
  • Merck Manual: Consumer Version. Endocrine Function. (https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/biology-of-the-endocrine-system/endocrine-function) Accessed 2/23/2022.
  • Society for Endocrinology. Hormones. (https://www.yourhormones.info/hormones/) Accessed 2/23/2022.

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