What are hormones?

Hormones are natural substances produced in the body. They help to relay messages between cells and organs and affect many bodily functions. Everyone has what are considered “male” and “female” sex hormones.

Keep reading to learn more about the female sex hormones, how they fluctuate throughout your life, and signs of a hormonal imbalance.

The two main female sex hormones are estrogen and progesterone. Although testosterone is considered a male hormone, females also produce and need a small amount of this, too.


Estrogen is the major female hormone. The lion’s share comes from the ovaries, but small amounts are produced in the adrenal glands and fat cells. During pregnancy, the placenta also makes estrogen.

Estrogen plays a big role in reproductive and sexual development, including:

Estrogen also affects the:

  • brain
  • cardiovascular system
  • hair
  • musculoskeletal system
  • skin
  • urinary tract

Estrogen levels can be determined by a blood test. While it can vary from person to person, these are what’s considered the normal ranges in picograms per milliliter (pg/mL):

  • Adult female, premenopausal: 15-350 pg/mL
  • Adult female, postmenopausal: <10 pg/mL
  • Adult male: 10-40 pg/mL

Levels will vary greatly throughout the menstrual cycle.


The ovaries produce the female sex hormone progesterone after ovulation. During pregnancy, the placenta also produces some.

The role of progesterone is to:

  • prepare the lining of the uterus for a fertilized egg
  • support pregnancy
  • suppress estrogen production after ovulation

Progesterone levels can be determined by a blood test. Normal ranges are in nanograms per milliliter (ng/mL):

before puberty0.1–0.3 ng/mL
during first (follicular) stage of menstrual cycle0.1–0.7 ng/mL
while ovulating (luteal stage of cycle)2–25 ng/mL
first trimester of pregnancy10–44 ng/mL
second trimester19.5–82.5 ng/mL
third trimester65–290 ng/mL


Small amounts of testosterone come from the adrenal glands and ovaries. This hormone plays a role in several body functions, including:

A blood test can determine your testosterone level. The normal range for females is 15 to 70 nanograms per deciliter (ng/dL).

Female sex hormones are integral to many body functions. But your hormonal needs change a great deal as you leave childhood and enter puberty.

They also change dramatically if you become pregnant, give birth, or breastfeed. And they continue to change as you near menopause.

These changes are natural and expected.

Everyone is different, but most females enter puberty between the ages of 8 and 13. And it all happens because of hormones.

The luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are produced in the pituitary gland. Production increases at puberty, which in turn stimulates the sex hormones — especially estrogen.

This increase in female sex hormones results in:

  • the development of breasts
  • the growth of pubic and armpit hair
  • an overall growth spurt
  • an increase in body fat, especially in the hips and thighs
  • the maturation of the ovaries, uterus, and vagina
  • the start of the menstrual cycle

The first menstrual period (menarche) happens about two to three years after the breasts begin to develop. Again, it’s different for everybody, but most females get their first period between the ages of 10 and 16.

Follicular phase

Every month, the uterus thickens in preparation for a fertilized egg. When there’s no fertilized egg, estrogen and progesterone levels stay low. This prompts your uterus to shed its lining. The day you start to bleed is day 1 of your cycle, or the follicular phase.

The pituitary gland starts to produce a little more FSH. This spurs growth of follicles in your ovaries. Within each follicle is an egg. As sex hormone levels drop, only a single, dominant follicle will continue to grow.

As this follicle produces more estrogen, the other follicles break down. Higher levels of estrogen stimulate an LH surge. This phase lasts about two weeks.

Ovulatory phase

Next comes the ovulatory phase. LH causes the follicle to rupture and release the egg. This phase lasts about 16 to 32 hours. Fertilization can only occur for about 12 hours after the egg has left the ovary.

Luteal phase

The luteal phase starts after ovulation. The ruptured follicle closes and the production of progesterone increases. This gets the uterus ready to receive a fertilized egg.

If that doesn’t happen, estrogen and progesterone decrease again and the cycle starts all over.

The entire menstrual cycle lasts around 25 to 36 days. Bleeding lasts between 3 and 7 days. But this, too, varies quite a bit. Your cycle may be quite irregular for the first few years. It can also vary at different times of your life or when you use hormonal contraceptives.

Estrogen, progesterone, and testosterone all play a role in female sexual desire — also called libido — and sexual functioning. Due to hormonal fluctuations, females are generally at the peak of sexual desire just before ovulation.

There’s generally less fluctuation in libido if you’re using hormonal birth control methods, which affect hormone levels. Your libido may also fluctuate less after menopause.

Undergoing surgery to remove your adrenal glands or ovaries cuts down on testosterone production, which can cause a drop in your libido.

During the luteal phase of your cycle, the rise in progesterone prepares your uterus to receive a fertilized egg. The uterine walls get thick and fill with nutrients and other fluids to sustain an embryo.

Progesterone thickens the cervix to protect the uterus from bacteria and sperm. Estrogen levels are also higher, contributing to the thickening of the lining of the uterus. Both hormones help milk ducts in the breasts to dilate.

As soon as conception takes place, you start to produce human chorionic gonadotropin hormone (hCG). This is the hormone that shows up in your urine and is used to test for pregnancy. It also boosts the production of estrogen and progesterone, preventing menstruation and helping to sustain the pregnancy.

Human placental lactogen (hPL) is a hormone made by the placenta. In addition to providing nutrients for the baby, it helps stimulate milk glands for breastfeeding.

Levels of another hormone called relaxin also rise during pregnancy. Relaxin aids in the implantation and growth of the placenta and helps stop contractions from happening too soon. As labor begins, this hormone helps relax ligaments in the pelvis.

Once pregnancy ends, hormone levels start to fall immediately. They eventually reach pre-pregnancy levels.

A sudden, significant drop in estrogen and progesterone may be a contributing factor in the development of postpartum depression.

Breastfeeding lowers estrogen levels and can prevent ovulation. This isn’t always the case, however, so you’ll still need birth control to prevent another pregnancy.

During perimenopause — the period leading up to menopause — hormone production in your ovaries slows down. Estrogen levels begin to fluctuate while progesterone levels start a steady decline.

As your hormone levels drop, your vagina may become less lubricated. Some people experience a decrease in their libido and their menstrual cycle becomes irregular.

When you’ve gone 12 months without a period, you’ve reached menopause. By this time, both estrogen and progesterone are holding steady at low levels. This typically happens around age 50. But like other phases of life, there’s great variation in this.

Decreased hormones after menopause may increase your risk of conditions such as thinning bones (osteoporosis) and cardiovascular disease.

Your hormones will naturally fluctuate throughout your lifetime. This is usually due to expected changes such as:

But a hormonal imbalance can sometimes be a sign of something more serious, such as:

  • Polycystic ovarian syndrome (PCOS). This is the most common endocrine disorder among young females. PCOS can cause irregular menstrual cycles and interfere with fertility.
  • Androgen excess. This an overproduction of male hormones. This can cause menstrual irregularities, infertility, acne, and male pattern baldness.
  • Hirsutism. Hirsutism is an increase in hair growth on the face, chest, abdomen, and back. It’s caused by excessive male hormones and can sometimes be a symptom of PCOS.

Other underlying conditions include:

You should always see your primary care doctor or gynecologist once a year for a routine wellness exam. Your doctor can discuss these changes and answer any other questions you may have.

Don’t wait until your annual exam if you’re experiencing unusual symptoms. See your doctor as soon as you can if you’re experiencing: