Hormones affect more than just mood. The vital chemicals enable daily bodily functions, reproduction, movement, and more.

We tend to think of certain times in life, such as puberty, pregnancy, and the transition to menopause as hormone-fueled, but the truth is that our hormones influence the health of our bodies and minds every single day.

What Are Hormones? A Description of the Messenger Chemicals

So what exactly are hormones? Hormones are special chemicals that travel through the bloodstream. “Think of them as the body’s internal WiFi,” says Randi Hutter Epstein, MD, (1) the author of Aroused: The History of Hormones and How They Control Just About Everything. They carry messages from the glands where they are produced to cells in different parts of the body. These chemical messages help to “turn on” or “turn off” cellular processes that control appetite, growth, stress, blood sugar, sleep cycles, sex drive, and sexual function, to name a few. (2)

Hormones Play an Important Role in Daily Healthy Living

“The term ‘hormonal’ has become synonymous with ‘moody,’" says Dr. Epstein. While hormones do affect mood, they do much more in the body than that, she says. (1)

Eat, Breathe, Love: Hormones Help You Do It All

Hormones are involved in some way in most bodily functions — from the basic (hunger, heart rate) to the complex (reproduction and emotion). (2)

Neurotransmitters: Hormones That Help the Brain Communicate With the Rest of the Body

Some hormones, such as serotonin and dopamine, also function as neurotransmitters — chemicals that relay messages between nerve cells in the brain and from neurons to muscles. Neurotransmitters help to coordinate movement and control mood and cognition. (3)

Hormones Are Produced by Glands That Make Up the Endocrine System

Glands are organs that secrete substances. Major hormone-secreting glands in the body include: pituitary gland, hypothalamus, thymus, adrenal glands, pancreas, thyroid, ovaries, and testes. (2) “The body’s network of hormone-producing glands and organs is called the endocrine system,” explains Caroline Davidge-Pitts, MB, BCh, an endocrinologist at the Mayo Clinic College of Medicine in Rochester, Minnesota. (4) Endocrinologists are hormone doctors.

Endocrinologists Help Diagnose and Treat Hormone-Related Health Problems

Because hormones are so important to proper functioning, small problems with hormone balance can cause serious health problems. But diagnosing a hormone problem can be complicated, and treatment usually involves more than just getting more — or less — of a certain hormone. (4)

The endocrine system is a complex web of interactions. “Hormones interact with each other and with many other systems of the body, including the immune system, in ways that we don’t yet understand,” says Epstein. (1)

Here’s a look at some key hormones and what research is showing us about their diverse roles in the human body.

Estrogen: The Female Sex Hormone

Estrogen: The Female Sex Hormone

Estrogen is sometimes called the female sex hormone, because it is produced primarily in the ovaries and plays an important role in the development of a woman’s reproductive system during puberty. Estrogen (actually a group of hormones — estrone, estradiol, and estriol are the main types) helps to regulate the menstrual cycle in a woman’s childbearing years. (5)

Men Have Estrogen Hormones, Too

“What many people don’t realize is that the male body makes estrogen too,” says Epstein. (1) Small amounts of estrogen are secreted by the adrenal glands and fat tissue in both sexes. The male body also makes estrogen by converting testosterone into estradiol — an important hormone for bone health in both men and women, says Dr. Davidge-Pitts. (4)

Estrogen also affects brain, liver, heart, and skin health and helps to regulate metabolic processes, such as cholesterol levels. (6)

Learn More About Estrogen

Testosterone: The Main Male Sex Hormone

Testosterone is the main sex hormone in men. (7)

It plays an important role in puberty for boys. Testosterone is the hormone responsible for many of the physical characteristics we consider typically male, including facial and body hair, muscle mass, and a deep voice. (8)

Androgens Are a Class of Hormones That Includes Testosterone

Testosterone is part of a class of hormones, called androgens, that are produced primarily by the testicles in men.

But testosterone isn’t solely a male hormone. The female body also produces small amounts of testosterone in the adrenal glands and ovaries. Women need a little bit of testosterone in the mix of hormones that helps maintain mood, energy level, sex drive, and other bodily functions. (9)

Testosterone Levels Decline With Age in Both Men and Women

Both men and women experience age-related declines in testosterone. In postmenopausal women, drops in testosterone can cause a decrease in sex drive. (7) In men, low testosterone, also known as "low T," has been linked to loss of bone and muscle strength, sleep disturbances, and problems getting or maintaining an erection. (7)

Some men seek testosterone replacement therapy (TRT) for these symptoms, though the possible long-term health effects of TRT have not been well-established. (7)

Learn More About Testosterone

Serotonin: A Happy Chemical

Serotonin is a hormone that doubles as a neurotransmitter. It’s sometimes known as the happy chemical, as it appears to play a role in regulating mood, and low levels of serotonin in the brain have been associated with mental health. (13)

Besides the brain, serotonin is involved in the function of several different organ systems. It helps to regulate appetite and digestion, bone health, and sex. Serotonin is also a precursor to melatonin, a chemical involved in the body’s sleep-wake cycle. (14)

As a neurotransmitter, serotonin is produced in the brain. But scientists are now discovering that the intestines — specifically the gut bacteria that lines them — also make serotonin, suggesting an important role for serotonin in gut health. (13)

Learn More About Serotonin

Progesterone: The Pregnancy Hormone

Progesterone, sometimes known as the “pregnancy hormone,” is a biggie for women who are trying to conceive. Progesterone plays an important role in initiating and maintaining pregnancy by getting the uterus ready to accept and grow a fertilized egg. (17)

Progesterone is produced by the ovaries and, in pregnant women, by the placenta. The placenta secretes high levels of the hormone throughout pregnancy, causing your body to stop ovulating and preparing your breasts to produce milk. (18)

Learn More About Progesterone

Replacing Estrogen and Other Hormones

As women age and approach menopause, the ovaries produce less estrogen. (3) Some women take prescription medications known as hormone replacement therapy HRT) or hormone therapy (HT) to help ease hot flashes, sleep issues, or other menopausal symptoms.

A large clinical trial in the early 2000s caused alarm in the medical community when it showed a link between certain types of estrogen replacement therapy and an increased risk of breast cancer and heart disease in postmenopausal women. (19) More current analyses do not show these same risks to be associated with estrogen replacement therapy. (20) But as with any medication, there are possible side effects, and you should discuss these with your doctor.

Learn More About the Wild History of Hormone Therapy

Where to Find Hormone Information and Resources

Browse a selective list of online resources that provide information, support, and searchable databases on hormone health and hormone disorders.

Learn More About Hormone Health Resources

Favorite Organizations and Pages for Essential Hormones Health Facts and Stats

American Society for Reproductive Medicine

This society of fertility specialists maintains a patient-focused website with easy-to-read educational pages on reproductive health topics, such as male and female infertility and assisted reproductive technologies (ART). The site also contains resources for finding a reproductive health professional.

Hormone Health Network From the Endocrine Society

The Endocrine Society is the world’s largest and most influential organization of endocrinologists (doctors who treat hormone disorders). The Hormone Health Network provides online resources for patients, including information on adrenal disorders, diabetes, thyroid problems, menopause, and transgender medicine and research. The site also contains an up-to-date physician referral directory with more than 6,500 Endocrine Society member doctors.

North American Menopause Society (NAMS)

Search for a menopause practitioner and read Q&As on perimenopause, hot flashes, hormone therapy, and other topics covered by the North American Menopause Society (NAMS), a nonprofit dedicated to promoting the health and quality of life of all women during midlife and beyond through an understanding of menopause and healthy aging.

National Institute of Mental Health

This government agency provides brochures and fact sheets in English and Spanish on common mental health disorders that explain what hormones do in the brain.

Favorite Resources for Becoming an Advocate

Partnership for the Accurate Testing of Hormones (PATH)

PATH formed in 2010 to help the clinical, medical, and public health communities improve patient care through more accurate and reliable hormone tests. PATH supports research that improves the diagnosis and treatment of hormone disorders.

National Association for Rare Disorders (NORD)

This leading nonprofit provides resources for patients and families impacted by rare diseases, including those related to hormone disorders.

PCOS Challenge From the National Polycystic Ovary Syndrome Association

Read patient stories, learn about PCOS fundraisers, and participate in groups and forums.

Favorite Hormone Health Blogs

Taking Charge of Your Fertility

Toni Weschler, author of Taking Charge of Your Fertility, blogs about natural birth control, getting pregnant with the fertility awareness method, and reproductive health.

The Period Revolutionary

Lara Briden, author of the Period Repair Manual, discusses PCOS, endometriosis, and many other menstrual cycle problems.


Cognifit is a healthcare company aimed at improving cognitive health. Their blog contains posts on all things related to brain health and neuroscience, including hormones that work as neurotransmitters.

Talking About Men’s Health

This blog was one of the top 10 men’s health blogs in 2018. Topics vary from natural remedies to help fight hair loss to what you need to know about testosterone replacement therapy.

Where To Find Hormone Health Clinical Trials

Clinical trials are medical studies aimed at preventing, diagnosing, and treating diseases. Check these resources for clinical trials on hormone disorders:

  • Break Through, at Antidote.me
  • CenterWatch
  • ClinicalTrials.gov
  • Program for Healthy Volunteers, from the National Institutes of Health
  • Research Match
  • Science 37

Editorial Sources and Fact-Checking


  1. Randi Hutter Epstein, MD. Phone interview. August 15, 2018.
  2. What Are Hormones, and What Do They Do? Hormone Health Network.
  3. Brain Basics. National Institute of Mental Health.
  4. Caroline Davidge-Pitts, MB, BCh. Phone interview. August 14, 2018.
  5. Estrogen (Oral Route, Paternaeral Route, Topical Application Route, Transdermal Route). Mayo Clinic. March 1, 2017.
  6. What Does Estrogen Do? Hormone Health Network.
  7. Could You Have Low Testosterone? MedlinePlus. August 14, 2018.
  8. Puberty. MedlinePlus. April 30, 2018.
  9. Therapeutic Use of Androgens in Women. Endocrine Society. October 2006.
  10. What Is Cortisol? Hormone Health Network.
  11. Curry A. The Connection Between Stress and Type 2. Diabetes Forecast. March 2016.
  12. Adrenal Glands. Johns Hopkins Medicine Health Library.
  13. Serotonin. Encyclopaedia Britannica.
  14. The Pineal Gland and Melatonin. Colorado State.
  15. Brookshire B. Explainer: What Is Dopamine? Science News for Students. January 17, 2017.
  16. Dopamine. NIH National Center for Biotechnology Information.
  17. What Is Progesterone? Hormone Health Network.
  18. Progesterone. University of Rochester Medical Center Health Encyclopedia.
  19. Writing Group for the Women’s Health Initiative Investigators. Risks and Benefits of Estrogen Plus Progestin in Healthy Postmenopausal Women: Principal Results From the Women’s Health Initiative Randomized Controlled Trial. Journal of the American Medical Association. July 17, 2002.
  20. Manson JE, Aragaki AK, Rossouw JE, et al. Menopausal Hormone Therapy and Long-Term All-Cause and Cause-Specific Mortality. Journal of the American Medical Association. September 12, 2017.


  • Gorney C. The Estrogen Dilemma. New York Times. April 14, 2010.
  • You and Your Hormones. Society for Endocrinology.
  • Chronic Stress Puts Your Health at Risk. Mayo Clinic. April 21, 2016.
  • Bergland C. Cortisol: Why the “Stress Hormone” Is Public Enemy No. 1. Psychology Today. January 22, 2013.
  • Cortisol Blood Test. MedlinePlus. August 14, 2018.
  • Dobbs D. The Depression Map: Genes, Culture, Serotonin, and a Side of Pathogens. Wired. September 14, 2010.
  • Brody J. Serotonin Syndrome: A Mix of Medicines That Can Be Lethal. New York Times. February 27, 2007.
  • Young SN. How to Increase Serotonin in the Human Brain Without Drugs. Journal of Psychiatry & Neuroscience. November 2007.
  • Davidow B. Exploiting the Neuroscience of Internet Addiction. The Atlantic. July 18, 2012.
  • Brookshire B. Dopamine Is … Is It Love? Gambling? Reward? Addiction? Slate. July 3, 2013.
  • Is Testosterone Therapy Safe? Take a Breath Before You Take the Plunge. Harvard Men’s Health Watch. December 31, 2017.
  • Testosterone Therapy: Potential Benefits and Risks as You Age. Mayo Clinic. December 13, 2017.


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