Progesterone: Characteristics and Functions

· April 20, 2019
Read all about progesterone in this interesting article!

Progesterone is a female hormone that belongs to the steroid family. A woman’s ovaries produce and release it. Along with estrogen, it’s one of the main hormones involved in a woman’s menstrual cycle and reproductive functions.

Even though it plays an important role in women’s bodies, it isn’t nearly as well-known as estrogen. Nevertheless, it’s so important that high or low levels of it can cause health problems and changes in a woman’s hormonal cycle.

In this article, discover its characteristics and functions.

The main characteristics of progesterone

A doctor at the University of Rochester discovered this hormone in 1933. He gave it this name based on its chemical and molecular makeup. It’s produced in three different places: the ovaries (in the corpus luteum, after ovulation), the suprarenal glands (which also produce adrenaline), and in the placenta during pregnancy.

Once your body produces progesterone, it stores it in your adipose tissue or body fat.

A close-up picture showing the word progesterone printed on a sheet of paper lying under a stethoscope.

After ovulation (when the body releases eggs), the ovaries start to produce progesterone in the corpus luteum. This is when it reaches peak levels in your body, which don’t regulate until you become pregnant or menstruate.

On the one hand, if you become pregnant, progesterone prepares your uterus for the gestation period. Ten weeks into pregnancy, that role will pass on to the placenta, which will produce all the progesterone you need for a healthy pregnancy until you give birth.

On the other hand, if you don’t get pregnant, your progesterone levels drop and your body’s endometrium (uterine lining) will start to shed, leading to menstrual bleeding.

Its main functions

Maintaining a regular menstrual cycle

Progesterone plays a role in starting the menstrual cycle. If no eggs are fertilized, your progesterone levels drop so your uterine lining sheds and menstruation begins.

As long as your progesterone levels are high, you won’t menstruate. But if your levels are low, you might experience bleeding even during pregnancy. Your uterine lining will think it needs to shed like it does at the beginning of your cycle.

Preparing the uterus for pregnancy

If an egg is fertilized, then progesterone prepares your uterus for the embryo and makes sure the pregnancy reaches full term. It’s the hormone that ensures that your uterus is stable and big enough for the embryo to grow. A while later, the placenta takes over to keep the pregnancy stable.

Preparing the mammary glands for lactation

While you’re pregnant, your mammary glands are preparing themselves to excrete milk. Progesterone is part of this process and is also the reason why your breasts start to grow. 

In other words, high progesterone levels tell your breasts they need to get ready to produce and release milk. But it’s not until after you give birth and start feeding your baby (thanks to prolactin and oxytocin) that your progesterone levels drop.

A mother is cradling her newborn baby in her arms, close to her neck.

Bone health

While estrogen keeps both healthy, progesterone helps form entirely new bone tissue. To do that, it interacts with your bone cells and stimulates them to help repair damaged bones.

Low progesterone levels and how they affect the central nervous system

It’s important to have adequate progesterone levels because this hormone plays a role in brain function, mood, and sexual libido. Research has shown that low progesterone levels can lead to mood swings, lack of sexual desire, anxiety, restlessness, and insomnia. This hormone also has a neuroprotective effect on the brain and prevents brain degeneration.

In conclusion, progesterone is a hormone that has a huge role both in pregnancy and menstruation. It also affects sexual desire and mood. If your progesterone levels are too low, your doctor can prescribe medication to increase them.