Estrogen, the “female” hormone, is a steroid molecule important for reproduction.

This is not the type of steroid you would want to take for body building though! Hormones are chemicals produced in the body, which have specific regulatory effects on certain cells or organs. They are essential for many bodily functions, including digestion, growth, and reproduction. Steroid hormones have a basic structure of four rings composed of carbon atoms.

Fast Fact: Even plants and fungi can produce estrogens, called phytoestrogens and mycoestrogens, respectively.

Estrogen is made from testosterone (yes, the “male” hormone) by the enzyme aromatase. In women, there are three forms of estrogen — estradiol, the main form in non-pregnant females, estriol, the primary estrogen in pregnant women, and estrone, the primary one in menopausal women. Most estrogen is produced in the ovaries, but is also made in the liver, breasts and adrenal glands.

In women, estrogen regulates the menstrual cycle and the development of secondary sexual characteristics. Secondary sexual characteristics are those that distinguish the two sexes of a species, such as breasts. Estrogen also accelerates metabolism, reduces muscle mass, and increases fat stores. Some types of depression in women are linked to fluctuating or chronically low levels of estrogen. In addition, around 80 per cent of breast cancers are hormone-sensitive cancers, which means they rely on estrogen to promote tumour growth.

Did You Know?
Starting in the 1950s, estrogen was used to stunt the growth of tall girls in the United States, Australia, and Europe. Although less common, this practice still occurs today, but it is controversial since it can lead to fertility issues.

If you thought estrogen was only important in women, think again. Guys need estrogen too! In men, estrogen is necessary for proper sperm development. Not enough estrogen leads to low sperm counts.

Fast Fact: It is thought that estrogen-like compounds in the environment (called endocrine disruptors because they block or mimic hormone activity in the body) may be responsible for lowered fertility rates, and therefore reduced populations of, susceptible wildlife species like frogs and fish.

For a little molecule with only 17 carbon atoms, estrogen does a lot!

Learn More!

What is estrogen?

Stunting Tall Girls' Growth may Impact Fertility

The Pill Off the Hook for River Estrogen

Estrogen Linked to Sperm Count, Male Fertilityalt

Article first published March 25, 2011.

Candace Webb

I graduated from the University of Ottawa in 2006 with a PhD in Biology. I am now a postdoctoral fellow at UCLA, studying the funky circadian rhythms of plants. Besides science, I love to write, hike, paint, bike ride, and hang out at the beach.


Une diplômée de l’Université d’Ottawa, j’ai reçu mon doctorat en biologie en 2006. Je suis présentement boursière postdoctorale à l’Université de Californie à Los Angeles, où j’étudie les rythmes circadiens des plantes. En plus des sciences, j’aime écrire, passer du temps à la plage et faire de la peinture, de la randonnée et du vélo.



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