All About the Endocrine System

The endocrine system is the body’s network for hormone production and distribution. It’s critical for keeping bodies healthy and for day-to-day functioning.

“The endocrine system helps regulate everything, such as how we’re responding to stress, blood pressure regulation, your weight, mood, sex drive, sleep, thirst, blood sugar levels, and heart rate — it has a vast array of effects that touch so many aspects of our health,” says Priya Jaisinghani, MD, a clinical assistant professor at NYU Langone Health and a board-certified endocrinology, obesity medicine, and diabetes physician in New York City.

Here’s everything you need to know about the endocrine system, its function, anatomy, and how to keep it healthy.

The endocrine system runs behind the scenes 24/7 from the day we’re born, says Mihail Zilbermint, MD, an associate professor of clinical medicine at the Johns Hopkins School of Medicine in Baltimore and a member of the Endocrine Society’s Clinical Affairs Committee. “From day one, a baby is already producing hormones,” he says. “Every single day of our life, we have hormones circling our body, telling us what to do.”

The key responsibility of your endocrine system is to create and release hormones into the bloodstream while monitoring their levels throughout your body.

Hormones are chemical messengers produced by the glands in our endocrine system. They target specific cells and attach to those cells’ surfaces, fitting like a key into a lock. There's no reaction if the hormone doesn’t fit into the cell’s lock.

• Metabolism (the process of transforming food into energy)
• Blood pressure 
• Blood sugar
• Fluid (water)
• Electrolytes (these are minerals that carry an electric charge)
• Body temperature
• Growth and development
• Sexual function
• Reproduction
• Sleep (and sleep-wake cycles)
• Mood

There are several components to the endocrine system, including glands, organs, and hormones.

Glands and Organs

• Hypothalamus The hypothalamus is located at the base of the brain. It keeps your body’s internal systems (such as digestion, sexual reproduction, the sleep-wake cycle, and the stress response) in balance, serving as a link between the endocrine and nervous systems. The hypothalamus acts as the endocrine system’s control center — it responds to chemical messages from nerve cells in your body and factors like your body temperature, nutrition and hydration, pain, stress and emotional cues, and light exposure and tells other organs when to pump out hormones.

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• Pancreas The pancreas is located in the back of your abdomen, Dr. Zilbermint says. The pancreas produces insulin and glucagon — two hormones that regulate blood sugar levels. The production of these hormones tends to be dysregulated in people with various types of diabetes.

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• Adipose Tissue (Body Fat) Adipose tissue (or fat tissue) is a type of connective tissue that runs throughout your body. There are three types of adipose tissue: white, brown, and beige. All types release hormones that influence our bodily functions. White adipose tissue, for example, stores fat as triglycerides, cushions organs and insulates the body, and also produces leptin, a hormone that tells you when you’ve had enough to eat.

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  Too much white adipose tissue (a cause of obesity) can lead to high levels of leptin (known as hyperleptinemia), which can make your body less responsive to the effects of leptin. When this happens (known as leptin resistance), your brain doesn’t get the message that you’re full or satiated, causing you to eat more, even if you have enough fat stored away.

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  Brown adipose tissue burns stored fat to generate heat in response to cold exposure, and beige adipose tissue can function as white or brown adipose tissue depending on your body’s needs.

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  Overall, body fat sends out several hormones, including leptin and adiponectin, and angiotensin.

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• Ovaries The ovaries are small, oval-shaped glands located on either side of the uterus that produce and store eggs and create the female sex hormones estrogen and progesterone.

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• Testicles The testicles are small, round organs underneath the penis that make sperm and testosterone.

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• Other Organs There are several organs in your body that release hormones but aren’t considered part of the endocrine system because they have other, more significant functions than making and releasing hormones. These include the stomach and small intestine, kidneys, liver, heart, and placenta (a temporary organ that’s created during pregnancy).

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• Pituitary Gland The pituitary gland is a small, pea-size gland at the base of the brain that’s nicknamed the “master gland” because it oversees hormone production by working in conjunction with the hypothalamus. “It often gets signals from the hypothalamus and then triggers other endocrine glands to release hormones,” Dr. Jaisinghani says.

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• Pineal Gland This tiny gland in the brain makes and releases melatonin, the hormone that cues your drowsiness at night.

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• Thyroid Gland Located in the front of the neck, this small, butterfly-shaped gland produces thyroid hormones, which regulate metabolism and energy levels.

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• Parathyroid Glands The parathyroid glands consist of four pea-size glands located behind the thyroid. They release parathyroid hormone, which controls calcium levels in the blood.

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• Adrenal Glands There are two triangle-shaped adrenal glands — one on top of each kidney. These glands produce and release essential stress hormones like cortisol, aldosterone, adrenaline (epinephrine) and noradrenaline (norepinephrine), which play many key roles, such as regulating blood pressure, electrolytes, and energy levels.

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Hormones

Your endocrine system sends hormones throughout your body. “Hormones are the chemical messengers that regulate various functions in the body, and they transmit signals to our organs, muscles and tissues, instructing them on what actions to take and when to perform them,” Jaisinghani says.

Hormones the endocrine system produces include:

• Adrenaline (epinephrine) gives your body a quick burst of energy to prepare for bouts of stress.

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• Adrenocorticotropic hormone (ACTH) tells your adrenal glands to produce cortisol and male sex hormones (androgens).

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• Aldosterone regulates salt (sodium), potassium, and blood pressure.

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• Angiotensin helps regulate blood pressure. It makes your blood vessels narrow and encourages your body to take in water and sodium.

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• Cortisol regulates your body’s stress response, metabolism, blood pressure, blood sugar, and sleep-wake cycle. It also suppresses inflammation.

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• Dehydroepiandrosterone (DHEA) is converted into testosterone.

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• Estrogen is one of the primary female sex hormones. It plays a key role in puberty, menstruation, pregnancy, and menopause. It also affects cholesterol and blood sugar levels, bone and muscle mass, blood flow, skin moisture, and the ability to focus.

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• Follicle-stimulating hormone (FSH) plays a role in sexual development and reproduction.

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• Ghrelin is known as the “hunger hormone” because it tells your brain when your stomach is empty.

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• Glucagon increases blood sugar levels.

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• Glucagon-like peptide 1 (GLP-1) is a gut hormone that signals the release of insulin and limits glucagon.

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• Gonadotrophin-releasing hormone (GnRH) stimulates the production of follicle-stimulating hormone and luteinizing hormone.

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• Growth hormone (GH) promotes human growth and development and boosts protein production.

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• Insulin moves glucose (sugar) out of the blood and into your body’s cells.

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• Insulin-like growth factor (IGF-1) manages growth hormone and helps promote normal growth and development.

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• Leptin is known as the “satiety hormone” because it tells your brain when your stomach is full.

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• Luteinizing hormone (LH) triggers ovulation (when the ovary releases an egg) and helps your body create hormones to support pregnancy.

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• Melatonin makes you drowsy when it gets dark, regulating your sleep-wake cycle.

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• Noradrenaline (norepinephrine) is both a neurotransmitter and a hormone. As a hormone, noradrenaline helps your body face stressful situations.

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• Oxytocin stimulates uterine contractions during childbirth and lactation after childbirth. Also known as the “love hormone,” oxytocin plays a role in sexual bonding and other social behaviors.

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• Parathyroid hormone (PTH) controls calcium, phosphorus, and vitamin D levels in the blood.

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• Progesterone is another primary female sex hormone. It helps the body prepare for and support pregnancy. It also plays a role in mood and promotes thyroid function.

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• Prolactin triggers lactation and breast tissue development.

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• Somatostatin stops the body from releasing certain hormones when they’re no longer needed.

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• Testosterone is the primary male sex hormone and is essential to male growth and development. Testosterone is also produced by females and affects bone strength, libido, and ovary function.

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• Thyroid hormone is actually made up of two hormones: triiodothyronine (T3) and thyroxine (T4). The primary function of the thyroid hormone is to control metabolism.

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With the right hormone balance, our bodies thrive. But sometimes our endocrine system creates too much or not enough of one of several hormones.

There are many reasons why this might happen. Endocrine gland dysfunction, family history of endocrine disease, stress, autoimmune conditions, and tumors can all disrupt hormone production and regulation, Zilbermint says.

Diabetes

• Type 1 Diabetes If you have type 1 diabetes, your body is unable to make the insulin it needs to move glucose into your cells. This occurs because the immune system mistakenly destroys the cells in the pancreas that make insulin. Type 1 diabetes is an autoimmune condition and must be treated with insulin daily.

• Type 2 Diabetes In type 2 diabetes, your body is unable to properly use the insulin your pancreas makes. It’s the most common type of diabetes and can appear at any age. Type 2 diabetes tends to occur in people with overweight or obesity and a family history of the disease. It can sometimes be managed with medications and lifestyle changes like a healthy diet and regular exercise. Sometimes it requires treatment with insulin.

• Gestational Diabetes This type of diabetes develops only during pregnancy. It occurs when your body is unable to meet your increased demands for insulin. Gestational diabetes can often be treated with medications and lifestyle changes, but sometimes requires insulin.

Thyroid Disease

There are two main types of thyroid disease. They are:

• Hyperthyroidism Hyperthyroidism, also called overactive thyroid, happens when the thyroid releases too much thyroid hormone, causing your metabolism to speed up. This leads to symptoms such as increased sweating, shakiness, anxiety, unexplained weight loss, rapid heart rate, diarrhea, and difficulty sleeping (insomnia). The condition can be treated with medications, and, occasionally, surgery.

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• Hypothyroidism Hypothyroidism, also called underactive thyroid, occurs when the thyroid doesn’t release enough thyroid hormone. This causes your metabolism to slow down, leading to unexplained weight gain, fatigue, brain fog, depression, anxiety, muscle weakness, and cold intolerance. The condition is usually treated with medication to replace your natural thyroid hormones.

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Cushing Syndrome

Addison’s Disease 

Polycystic Ovary Syndrome 

You can’t always prevent hormone imbalances or endocrine-related diseases. But there are steps you can take to keep your body healthy.

• Maintain a healthy weight.
• Eat nutritious foods.
• Exercise regularly.
• Get quality sleep.
• Limit alcohol consumption.
• Avoid or quit smoking.

Pay attention to any family history of endocrine-related conditions, too. Tell your family doctor if your parents have diabetes, thyroid disease, or PCOS. “The doctor can help you understand your risk of developing these conditions and what symptoms to look for,” Zilbermint says.

• The endocrine system consists of organs and glands that produce chemical messengers known as hormones.
• Together, the endocrine organs, glands, and hormones regulate key functions in the body, such as metabolism, blood pressure, sleep-wake cycle, and more.
• Too much or too little of a hormone can disrupt body functions and cause disease.