What is Progesterone and Why Do We Need It?

Progesterone can be thought of as a hormonal balancer, particularly when it comes to the estrogens. Progesterone is a steroid hormone made by the corpus luteum of the ovary at ovulation, and in smaller amounts by the adrenal glands. It is the precursor, or substance from which most of the other steroid hormones are derived, including cortisol, androstenedione, the estrogens and testosterone. Progesterone has a remarkable repertoire of important jobs from normalizing blood sugar levels and facilitating thyroid hormone action to regulating menstrual cycles and maintaining a healthy pregnancy. The survival of the embryo in the womb absolutely depends on this vital hormone. Progesterone also has natural calming and diuretic properties, and it enhances the positive effects of estrogen, while preventing the problems associated with estrogen dominance. Unopposed estrogen can build to unsafe tissue levels that can lead to a strong risk for breast cancer and reproductive cancers. While estrogen levels drop only 40-60%, at menopause progesterone levels may drop to near zero in some women, resulting in estrogen dominance and the array of symptoms that go with it. Supplementation of natural bio-identical progesterone has been shown to restore hormonal balance, especially during perimenopause and menopause.

Available as: Prometrium® (progesterone in peanut oil), compounded topical cream, compounded capsules (immediate or sustained release), compounded lozenges. Progesterone is a steroid hormone. It has 21 carbon atoms while estrogen has only 19. It is a precursor, or building block for estrogen but also conveys its own unique message to cells. Estrogens directs cells to grow and multiply, while progesterone directs them to slow their growth and mature normally. Progesterone controls and modifies the message of estrogen. Progesterone is produced only by the corpus luteum, the cyst that remains after the egg is expelled during ovulation. Unlike estrogen, progesterone is not made by the conversion of other steroid hormones in peripheral tissue, such as fat, skin and muscle. Progesterone production occurs only after ovulation.

ProgesTINS are synthetic versions of progesterone. Progestins have a chemical make-up similar to progesterone. These compounds bind to the progesterone receptors in cells but they are unable to deliver the entire message. They are only able to direct the cell to perform a limited amount of the progesterone message. The progesterone hormone receptor complex is very specific. If one carbon atom of progesterone is changed, the message to the target tissue is also changed. Progesterone is metabolized to estrogen, testosterone and cortisol in women. Progestins, altered progesterone molecules, can create a roadblock in this cascade. The altered structure of progestins not only affects the progesterone message; it also results in unwanted side effects. However, the short-term use of Progestins is helpful in treating vaginal bleeding and protecting the uterus from cancer caused by estrogen exposure.

Functions of Progesterone:

• Promote and maintain pregnancy

• Diuretic; decrease water retention

• Increases thyroid function

• Natural antidepressant and anti-anxiety hormone

• Increase libido (sexual desire)

• Decreases uterine contractions (cramping). Good for menstrual cramps

• Decrease estrogen receptors

• Promotes natural cell maturation (decreases cancer risks)

• Decreases cell multiplication caused by estrogen

• Promotes normal cell death

• Decrease frequency of seizurs

The word progesterone is derived from 2 words, PROmote and GESTation. Progesterone is the only hormone needed to maintain a pregnancy. Progesterone is made after ovulation. Its function is to develop and mature the lining of the uterus so that it can sustain a pregnancy. Progesterone made by the corpus luteum sustains the pregnancy until the placenta is able to make enough progesterone to maintain the pregnancy. The placenta makes enormous amounts of progesterone. The body makes 2 to 4 milligrams a day of progesterone. But during pregnancy the body makes 200 to 400 milligrams a day of progesterone.

Many infertility specialists use progesterone suppositories when treating women with infertility problems. Women who are deficient in progesterone may have frequent early miscarriages. The addition of progesterone will often allow the uterus to maintain the early pregnancy until the placenta takes over the production of progesterone. Progesterone is also used in assisted reproduction of in vitro fertilization. It helps provide an optimal uterine environment in which fertilized eggs can grow. Progestins (synthetically altered progesterone) are not used to maintain pregnancies. The addition of progestins will not maintain a pregnancy and is also associated with cardiac defects in the fetus.

Another major function of progesterone is to regulate the activity of estrogen. I discussed the issue of how estrogens make more estrogen receptors in the presence of excess estrogen (see “What is Estogen”). Progesterone is able to decrease the production of estrogen receptors. This decreases the cell’s ability to overreact to excessive levels of estrogen. This is one of the mechanisms by which progesterone protects the body from estrogen-induced cancers of the uterus and breasts. Another by promoting cell differentiation. Progesterone promotes normal cell development and can override estrogen’s message to multiply. Estrogen and progesterone work together to better in balance than they do alone or out of balance.

Progesterone blocks the action of a hormone called aldesterone. Aldesterone causes the body to store water in the presence of dehydration. Progesterone blocks aldosterone receptors and allows the body to release excess water. Progesterone behaves like a natural diuretic. Progesterone decrease thyroid binding globulin. Estrogen increases thyroid binding globulin levels, which inactivates thyroid hormone. This slows the body’s metabolism and allows the storage of fat and energy for a future fetus. Progesterone, on the other hand, decreases thyroid binding globulin levels, thereby increasing the amount of active thyroid hormone. Thyroid hormone can now stimulate the utilization of the fat store for energy. All patients being treated for hypothyroid disease should be supplemented by progesterone.

Progesterone is very important to the normal functioning of the brain. A blood-brain barrier protects the brain from outside substances. Only what is necessary is allowed to cross this barrier. Over 66% of the progesterone made by the body is concentrated in the brain. In the brain, progesterone can bind to GABA receptors. These receptors are responsible for maintaining an appropriate mood. GABA receptors are the receptors to which antidepressant drugs and anti- anxiety drugs bind to produce their effects. Studies show that these mood-altering drugs work because they elevate the concentration of a progesterone by-product. Therefore, progesterone can be prescribed as a natural antidepressant and anti-anxiety treatment.

Progesterone also assists in the myelinization of nerve cells. Myelin forms the insulation around nerve cells. Nerves and electrical wires are both alike in that they conduct electrical current. Electrical wires need rubber insulations; nerves need myelin insulation. Insulation allow current to be transmitted without interruption. Seizures are the result of an abnormal flow of electrical current in the brain. Progesterone lowers seizure activity. It decreases the rate of seizures by preventing short circuits, which cause seizures. In general, progesterone seems to increase concentration and allow clearer thinking when present in proper amount. Progesterone increases libido, both directly and indirectly. Normally there is a small rise in progesterone prior to ovulation. Studies have shown that women initiate sex more often immediately prior to ovulation. This may be due to a direct effect of progesterone or an increase in the metabolism of progesterone to testosterone. In either case, progesterone positively affects sex drive.

Progesterone relaxes smooth muscle, which is found in the uterus. Progesterone can relax smooth muscle contraction. The contractions of the uterine smooth muscle during the menstrual cycle are experienced as menstrual cramps. Progesterone can decrease the intensity of menstrual cramps. Smooth muscle also lines blood vessel walls; therefore, progesterone can relax blood vessels. This effect may protect from heart attacks. A study showed that in primates (apes), the addition of progesterone made it relatively impossible to induce heart attacks in these animals. Further study is needed to see if progesterone has the same effect on the human heart. Progesterone effects the bone metabolism. It stimulates a cell in the bone called the osteoblast, which is responsible for new bone formation. The osteoblast uses calcium to form new bone. Bone is constantly in a state of development. Osteoclasts break down old bone, while new bone replaces the old bone under the direction of osteoblasts, which are influenced by progesterone. Estrogen regulates osteoclasts to make sure they do not break down the bone too rapidly. This is another example of how estrogen and progesterone work together. When progesterone and estrogen are available in their proper relationship, they promote good health. In the absence of sufficient quantities of progesterone, the body begins to make androgens (male hormones) to regulate the effect of estrogen. Androgen production in women produces male pattern baldness and hirsuitism (facial hair). Male pattern baldness includes receding hairlines, bald spots in the back of the head and thinning hair. This occurs when the ovary is primarily producing testosterone in addition to androgens produced by the adreanal gland. When ovulation does not occur, progesterone is not produced. Androgens are the only defense against overexposure to estrogen in the absence of progesterone. To understand progesterone’s role in hair growth, you need only to examine the hair and nails of a pregnant woman. Most women report that their hair and nails became longer and thicker when pregnant. During pregnancy, the progesterone level is maintained at a maximum level. Unfortunately, women report reversal of these benefits shortly after delivery.

Progesterone Deficiency:

Progesterone deficiency can cause or make worse:

• Irregular/heavy bleeding

• Breast tenderness

• Depression, fatigue, and poor concentration

• Fibrocystic breast


• Decrease Libido

• Fibroid growth

• Endometriosis

• Water retention and bloating

• Fat gain around hips and thighs

• Bone loss

• Hair loss

• Breast and uterine cancer

Progesterone Excess:

• Euphoria

• Prolonged excessive use lead to symptoms of progesterone deficiency

Points to Remember:

1. Balance in the menstrual cycle is essential.

2. Estrogen’s message to cells is to GROW.

3. Progesterone’s message to cells is to stop growing and DEVELOP.

4. Hormones have checks and balances. Each hormone in the body has a counterpart hormone that regulates its function

5. Estrogen excess and progesterone deficiency can cause indentical symptoms in women.

Information taken from “Are your Hormones Making you Sick?” by, Eldred Taylor, MD, Ava Bell- Taylor, MD Physicians Natural Medicine, Inc., Feb, 2006

Hormone Therapy 

Menopause and Hormonal Imbalance
The Anatomy of a Hot Flash
“Tired but Wired” - Fatigue, Stress and Hormone Imbalance
Facts On Hormone Balance Issues
Hormone Imbalance and PMS
All About Natural (Bio-identical) Hormones
What is Progesterone and Why Do We Need It?
Hormone Balance and Osteoporosis
Estrogen Dominance and Low Thyroid
Depression and Mood Swings
Hormone Imbalance and Hysterectomy
Hormone Imbalance and Insulin Resistance
Vitamin D Deficiency 
What is Adrenal Fatigue?
Saliva Testing
Bio-Identical Hormones: What You Need To Know
What is Testosterone?
What is Estrogen?
Bioidentical Hormone Abstract
The Bioidentical Hormone Debate
Bio-Identical Hormone Therapy
How To Collect Saliva