Many people, especially women, are familiar with the name of the hormone Progesterone. This hormone has multiple important functions to play in the body and thus maintaining healthy levels of progesterone is crucial to the overall health of the female body.

This detailed write-up consists of an elaborate report on the functions of progesterone and discusses what causes progesterone to be low. Ways to treat low progesterone levels are also mentioned at the end of the article.

1. What is Progesterone?

Progesterone is a natural hormone that has a very important role to play in a woman’s reproductive system. A gland known as the corpus luteum produces the hormone progesterone in our body during the second half of the menstrual cycle. Although the corpus luteum in the ovaries is the main site of progesterone production in human beings, this hormone is also produced in smaller quantities by the ovaries themselves, the adrenal glands and, during pregnancy, the placenta itself.

The hormone progesterone plays an important role in menstruation as well as pregnancy.

2. What are the functions of Progesterone?

Though the main functions of the hormone progesterone are related to the female reproductive system, there are certain other important roles that this hormone plays in our body. The following is a list of functions of progesterone in our body.

2.1. Regulation of the Menstrual Cycle

The hormone progesterone plays the most important role in the regulation of the menstrual cycle. It prepares the uterine lining, also known as the endometrium, for implantation in case the egg is fertilized. When fertilization does not occur, progesterone levels in the female body drop significantly which results in the shedding of the uterine lining and causes menstruation.

2.1.1. Preparation of the Uterine Lining (Endometrium)

This hormone is responsible for preparing the uterine lining or the endometrium for the potential implantation of a fertilized egg cell.

During the first half, also known as the follicular phase, of the menstrual cycle, increasing levels of a hormone known as oestrogen stimulates the growth and thickening of this lining.

After ovulation the levels of the hormone progesterone increase; progesterone further enhances the development of the uterine lining or endometrium and prepares it to support the implantation and growth of a fertilized egg.

2.1.2. Suppression of Ovulation

Progesterone helps to suppress or prevent the release of other additional eggs during the luteal phase of the menstrual cycle. This, in turn, plays a crucial role in preventing the birth of fraternal twins or fertilization off multiple eggs to create multiple zygotes in the same cycle.

2.1.3. Maintenance of the Uterine Lining

If fertilization of the egg occurs and the process of pregnancy begins, progesterone levels in the female body increase. As a result, the uterine lining is maintained and is prevented from shedding (which will lead to miscarriage if occurs). Progesterone is mainly produced by the corpus luteum, which is a temporary endocrine structure present in the ovaries of the female reproductive system.

2.1.4. Inhibition of Uterine Contractions

Progesterone plays a crucial role in preventing contractions of the uterine muscles as it has a relaxing effect on the smooth muscles of the uterus. This is the most important role to play during the luteal phase of the menstrual cycle in order to maintain a relaxed, quiet and non-contracting environment in the uterus, making the uterine environment conducive for implantation and pregnancy.

2.1.5. Timing of Menstruation

The hormone progesterone is responsible for maintaining the timing of the menstrual cycle. In case fertilization of the egg cell (referred to as the ovum) does not occur, progesterone levels in the female body start dropping drastically, resulting in the shedding or break down of the endometrial tissue, causing menstrual bleeding.

2.1.6. Regulation of the Length of Menstrual Cycle

Progesterone also regulates the length of one’s menstrual cycle. This is because the length of your menstrual cycle (the duration between the first day of one period and the first day of the next period) largely depends on the timing of ovulation as well as the length of the luteal phase.

2.2. Support of Pregnancy

Once the egg is fertilized, progesterone triggers the growth of blood vessels that supply the endometrium (the womb), and stimulates the glands that secrete nutrients to nourish the embryo in its earliest stage.

Progesterone enables the uterine lining to allow for the embryo to develop and prevents its shedding (which can lead to ‘miscarriage’). In the later stages of pregnancy, the placenta itself takes over the production of progesterone.

During pregnancy, progesterone levels increase with each trimester, reaching their highest level in your third trimester (weeks 28 to 40 of pregnancy). The level of progesterone in the female body declines in the years leading up to menopause, when ovulation stops.

2.2.1. Implantation and Early Pregnancy

Once the ovum is fertilized, the fertilized egg cell (referred to as the zygote) travels down the fallopian tube, eventually attaching itself to the uterine lining or the endometrium. The hormone progesterone then prepares the endometrium for implantation by thickening it and making it more receptive to the growing embryo.

2.2.2. Maintaining the Uterine Lining

Progesterone supports the uterine lining (endometrium) even after implantation has occurred. The increase in secretion of this hormone makes sure the endometrium stays strong and prevents it from shedding, ensuring a stable and safe environment for the growth of the foetus.

2.2.3. Suppressing Uterine Contractions

This hormone plays a crucial role in suppressing uterine contractions as it has a relaxing effect on the uterine muscles. Suppressing uterine contractions is really important to prevent preterm labor. The role of progesterone in to maintain a non-contracting and quiet environment for the growing fetus.

2.2.4. Supporting the Placenta

Progesterone plays a very significant role in the development and sustenance of the placenta after implantation. The placenta is an organ that develops in the uterus during pregnancy and provides oxygen and nutrients to the growing baby or the fetus. Progesterone ensures the proper functioning of the placenta and facilitates the exchange of nutrients as well as waste material between the mother and the baby.

2.2.5. Inhibiting the Maturation of Additional Eggs

Another key role of the hormone progesterone is to inhibit the release of additional eggs. In other words, progesterone suppresses ovulation to prevent an additional pregnancy; that is, it prevents the mother from getting pregnant while already carrying a fetus. It tries to prevent the birth of twins (both identical and fraternal).

2.2.6. Modulating the Immune System

During pregnancy, there are certain changes in the maternal immune system in order to make it possible for the mother to tolerate the presence and growth of the fetus. Progesterone is the hormone responsible for regulating the mother’s immune system and minimizing the chances of the maternal immune system rejecting the fetus.

2.2.7. Breast Development for Lactation

The hormone progesterone, along with another hormone estrogen, prepares a woman’s breast tissues for lactation. It promotes the growth of mammary glands and milk-producing alveoli; this prepares the woman’s body for the process of breastfeeding.

2.2.8. Supporting Fetal Development

Progesterone plays a crucial role in supporting the development of the fetus. It supports the growth of various organs and systems of the growing features, such as the nervous system, respiratory system, and gastrointestinal tract.

2.2.9. Preventing Menstruation

As mentioned numerous times earlier, one of the key roles of progesterone is to thicken and strengthen the uterine lining, and prevent menstruation (as it prevents the shedding of the uterine lining or endometrium).

2.2.10. Labor Inhibition

Progesterone prevents contractions in the uterus in order to prevent labor during early and middle stages of pregnancy. Towards the end of pregnancy progesterone levels in the female body drop, allowing contractions to occur to initiate labor and cause delivery.

2.3. Breast Development

Progesterone, along with another hormone oestrogen, plays a crucial role in the development of mammary glands. This hormone also prepares the breasts for lactation and helps in maintaining good breast health.

2.3.1. Stimulation of Mammary Gland Growth

The hormone progesterone, along with oestrogen helps in the growth and survival of mammary gland cells. Mammary glands produce milk during lactation. Also, it is under the influence of progesterone that the mammary glands in human females develop and increase in size.

2.3.2. Alveolar Development

The basic components of mature mammary glands are the alveoli lined with milk-secreting cuboidal cells and surrounded by myoepithelial cells. Alveoli can be defined as a grape-like cluster of cells where milk production takes place. Progesterone prepares the alveoli for milk production, which is essential during the process of pregnancy and lactation.

2.3.3. Glandular Duct Development

There are glandular ducts present in the breast tissues and these ducts act as conduits for transporting milk from the alveoli to the nipple during breastfeeding. The hormone progesterone plays an important role in the development and maintenance of these glandular ducts, especially when it comes to the context of pregnancy and lactation. Progesterone assists in the elongation as well as branching of the glandular ducts.

2.3.4. Preparation for Lactation

Progesterone, along with prolactin (a hormone responsible for lactation, certain breast tissue development and milk production) is responsible for ensuring that the breast tissue is adequately prepared to go through the process of lactation. The role of progesterone in the development of the glandular ducts is significant during pregnancy and the early stages of lactation. Prolactin takes over the process of lactation once the baby is born. Later when lactation stops, progesterone levels drop and the breast tissues return to their original, non-lactating state.

2.3.5. Maintaining Breast Health

Progesterone along with the hormone oestrogen helps in maintaining the overall health of the breast tissues in human females. This hormone (progesterone) promotes the proliferation as well as differentiation of the cells present in breasts, which is very important for the normal and healthy functioning of the breasts.

2.4. Cervical Mucus

Oestrogen and progesterone secretions together determine changes in the secretion of cervical mucus or discharge. This makes the environment of the cervix and vagina either less or more conducive for intercourse as well as transportation of sperm.

2.4.1. The Menstrual Period (from Day 1 to Day 5)

During this phase of the menstrual cycle, period bleeding occurs and the secretion of cervical mucus or discharge is reduced to minimal. This is because the uterine lining is shedding and there is little to no need of the female body to support implantation or a pregnancy.

2.4.2. The Early Follicular Phase (from Day 6 to Day 9)

After the menstrual period is over, the early follicular phase begins, where cervical mucus becomes a bit more noticeable but is still minimal. Vaginal discharge, at this stage of the menstrual cycle, may be sticky or tacky in texture.

2.4.3. The Mid-Follicular Phase (from Day 10 to Day 14)

At this stage, the fertile phase of the menstrual cycle begins. Both oestrogen and progesterone levels rise, resulting in abundant secretion of the cervical mucus. Vaginal discharge during this phase of the cycle typically has a stretchy or slippery texture.

2.4.4. Ovulation (around Day 14)

This is the time where cervical mucus reaches its peak in both quality and quantity. During ovulation, cervical mucus is the most fertile and provides an ideal environment for the survival and transportation of sperm cells. Vaginal discharge during ovulation is stretchy, transparent, and slippery in nature, and facilitates the journey of the sperm towards the released egg to cause fertilization.

2.4.5. The Post-Ovulatory Phase (from Day 15 to Day 28)

The post-ovulatory stage of the menstrual cycle is also known as the luteal phase and in this part of the cycle, there are noticeable changes in the cervical mucus or vaginal discharge. It becomes thicker and stickier, making it less conducive for the survival or transportation of sperm cells. The change in texture occurs due to rising levels of progesterone, which is the most significant component of the luteal phase of the menstrual cycle.

2.4.6. Premenstrual Phase (Days leading to Menstruation)

This phase is characterized by a significant decrease in the secretion of the cervical mucus. Discharge at this stage of your menstrual cycle is typically cloudy and thick and has a sticky texture to it. In other words, cervical mucus during the premenstrual phase is ‘non-fertile’.

After this phase comes the menstrual period, marking the beginning of the next menstrual cycle. The secretion of cervical mucus again goes down to minimum and any remaining vaginal discharge is expelled along with the period flow. All the next phases are repeated in a cyclic manner again.

2.5. Temperature Regulation

Progesterone has another function; it regulates our body temperature. This hormone’s role in the regulation of body temperature is discussed in detail below.

2.5.1. Basal Body Temperature (BBT)

The hormone progesterone is often referred to as ‘the warming hormone’ due to its role in regulating a woman’s Basal Body Temperature or BBT. Progesterone levels in the body increase after ovulation, which is the most fertile stage of the menstrual cycle, followed by the release of an egg or ovum. This increased secretion of the hormone leads to an increase in the female’s basal body temperature.

Basal Body Temperature or BBT refers to the temperature of your body when it is at rest and is typically measured in the morning before you have performed any physical activity. Before ovulation, the average basal body temperature of a woman ranges between 96 and 98 F, i.e., 35.5 and 36.6 C, whereas, after ovulation, BBT rises to approximately 95 to 97 F, i.e., 36.1 to 37.2 C.

2.5.2. The Luteal Phase

It is in the luteal phase that the basal body temperature increases due to elevated levels of progesterone in the female body. This elevation in a woman’s Basal Body Temperature or BBT is often used as a natural method of tracking her fertility as the rise in BBT suggests that the fertility window has already passed.

2.5.3. Thermoregulation in Pregnancy

Throughout the process of pregnancy, progesterone levels in the mother’s body remain high to support the growth and development of the baby or the foetus. As this hormone has a mild thermogenic effect on the body, the body temperature of pregnant women remains slightly higher compared to other women.

2.5.4. Heat Dissipation

Although high progesterone levels lead to a rise in Basal Body Temperature or BBT, this hormone is not responsible for major temperature regulation of the body in response to external temperature changes or fluctuations. For this purpose, the body mostly relies on other mechanisms of temperature regulation such as sweating and blood vessel dilation or constriction to dissipate or retain heat respectively in response to temperature changes in the external environment.

2.6. Uterine Relaxation

Progesterone plays a crucial role in relaxing the uterine muscles so the growth of the foetus remains undisturbed. Here is how progesterone helps in uterine relaxation:

2.6.1. Muscle Relaxation

The hormone progesterone acts as a muscle relaxant during the process of pregnancy. It prevent the uterine muscles from contracting prematurely in order to prevent preterm labor. Progesterone helps in keeping the uterine environment relaxed and conducive for the baby’s growth and development.

2.6.2. Inhibition of Excitability

Progesterone also inhibits the excitability of the smooth uterine muscle cells. This hormone reduces the sensitivity of the uterine muscles to electrical signals that may trigger contractions, ensuring a relaxed, non-contracting environment for the growing foetus.

2.6.3. Suppression of Other Hormones

This hormone (progesterone) also inhibits the sction of certain other hormones, such as oxytocin, which triggers contractions in the uterine muscles. Oxytocin is popularly referred to as the ‘labor hormone’ as this hormone stimulates the uterus to contract during labor.

2.6.4. Maintaining the Uterine Lining

As mentioned earlier, progesterone maintains the endometrium and keeps it strong enough to support pregnancy.

2.6.5. Preventing Premature Birth

By keeping the uterine muscles free from contractions, progesterone prevents preterm labor, which could lead to premature birth.

2.7. Bone Health

Here is a list of ways progesterone helps in maintaining proper bone health.

• By balancing estrogen
• Maintaining bone density
• By inhibiting osteoclast activity
• By protecting against bone loss
• By its anti-inflammatory effects

2.8. Neuroprotection

A list of ways in which progesterone contributes to neuroprotection in stated below.

• Anti-inflammatory effects
• Antioxidant activity
• Myelin protection
• Neurotrophic effects
• Neurosteroid properties
• Neuroinflammation Modulation
• Neurogenesis

2.9. Mood Regulation

Progesterone helps in regulating your mood by interacting with neurotransmitters and receptors in your brain. Progesterone therapy is also used to alleviate mood symptoms in some health conditions.

2.10. Contraception

Progesterone is used in contraception in order to prevent pregnancy and it does so by inhibiting ovulation, thickening the vaginal discharge to inhibit sperm movement and altering the endometrium to deter implantation. It is available forms of birth control pills, injections, implants, and intrauterine devices (IUDs).

2.11. Hormone Replacement Therapy

In HRT, progesterone is used to balance the effects of oestrogen in women who are in premenopausal or menopausal age. It reduces the risk of endometrial cancer and can be administered through pills, creams, and patches.

2.12. Fertility Treatment

It is a vital component for fertility treatment and can be administered in various forms like vaginal suppositories, injections, oral capsules, etc. Progesterone also increases the chances of a successful pregnancy in assisted reproductive techniques like In Vitro Fertilization (IVF).

3. What causes Progesterone to be Low?

There are several conditions that can cause progesterone levels to be low in one’s body. Given below is a list of reasons why progesterone levels in your body may be low:

3.1. Annovulation

This is a condition where the ovary does not release an egg during a menstrual cycle. As this hormone is mainly secreted from the corpus luteum, which forms after ovulation, anovulation will lead to low progesterone levels in the body.

3.2. Polycystic Ovary Syndrome (PCOS)

This is a hormonal disorder and is typically characterized by the formation of multiple cysts in a woman’s ovaries. Polycystic Ovary Syndrome is the commonest cause of anovulation and one of the leading causes of female infertility.

3.3. Stress

Chronic stress can cause hormonal imbalances (especially of sex hormones) in your body. High stress levels disrupts the production of hormones, including progesterone. In this way, severe stress can lead to low progesterone levels in the body.

3.4. Low Body Fat

It is common to have a low body fat percentage among female athletes as well as patients suffering from eating disorders. Adequate body fat is a necessity when it comes to healthy production of sex hormones. Thus, females with low body fat are susceptible to low levels of progesterone.

3.5. Certain Medicines

There are certain types of birth control pills and hormone therapies that interfere with the natural production of hormones in the body. These medications can, thus, negatively affect low progesterone levels in your body.

3.6. Chronic Illness

Chronic illnesses such as Type 2 Diabetes, Autoimmune Diseases, Chronic Kidney Disease, etc. can negatively affect the production of sex hormones in the body, leading to hormonal imbalances, including changes in the levels of progesterone in the body.

3.7. Thyroid Disorders

Here is how thyroid disorders can cause low progesterone levels in females:

3.7.1. Hypothyroidism

This is a condition characterized by an underactive thyroid gland, leading to low levels of thyroid hormones. Insufficient thyroid hormones may lead to irregular menstrual cycles and cause a lack of ovulation (anovulation), resulting in low progesterone levels.

3.7.2. Hyperthyroidism

This is a condition characterized by an overactive thyroid gland, leading to higher levels of thyroid hormones. Excessive thyroid hormones can cause altercation in menstrual cycles, and cause shorter and irregular menstrual bleed. This will affect the production of progesterone and lead to lower levels of it in your body.

3.8. Ovarian Dysfunction

Conditions that affect the ovaries, such as ovarian cysts, PCOD & PCOS can cause progesterone levels to be lower.

3.9. Chronic Illness

Certain chronic conditions including Type 2 Diabetes, Obesity, Autoimmune Diseases, and Chronic Kidney Disease can lead to lower levels of the hormone progesterone.

3.10. Luteal Phase Deficiency

Sometimes the luteal phase in the menstrual cycle may be shorter than usual. This restricts the secretion of the hormone progesterone and may cause low levels of it in your body.

3.11. Diet & Nutrition

Low levels of progesterone in the body could also be the result of poor diet and insufficient intake of Vitamin B6 and zinc can lead to low progesterone.

4. What are the effects of low progesterone on the body?

The effects of low progesterone levels in the body include:

• Menstrual Irregularities
• Difficulty Getting Pregnant and Susceptibility to Miscarriage
• Severe Premenstrual Syndrome (PMS)
• Premenstrual Dysphoric Disorder (PMDD)
• Mood Changes
• Hot Flashes
• Sleep Disturbances
• Poor Bone Health and increased Risk of Osteoporosis
• Low Libido
• Uterine Abnormalities
• Breast Changes
• Skin Issues

5. What are the symptoms of low progesterone levels in the body?

If your progesterone level drops below normal, your body may show various symptoms. Common symptoms that occur due to low progesterone levels are stated below.

• Irregular Menstrual Cycles (including missed periods, longer or heavier periods, or irregular bleeding during the menstrual period)
• Severe Premenstrual Syndrome or PMS (irritability and mood changes)
• Infertility
• Low Libido and Vaginal Dryness
• Sleep disturbances, breast changes, and skin issues

6. How are low progesterone levels treated?

Ways to treat low progesterone levels are:

• Progesterone Supplementation
• Hormone Replacement Therapy (HRT)
• Fertility Treatment
• Lifestyle and Dietary Changes
• Addressing Underlying Causes
• Herbal and Natural Remedies
• Regular Monitoring

7. What is progestin?

Progestin is nothing but an artificial synthetic form of the hormone progesterone. When progesterone levels in the body are lower than the normal or desired quantity, progestin is used, which mimics the effect of progesterone in the body. The synthetic hormone progestin form of a pill, injection, gel, suppository, cream or patch depending on its dosage as well as use.

8. What is progestin generally prescribed for?

Given below is a list of reasons progestin is prescribed for:

• To properly regulate the menstrual cycle and prevent amenorrhea (i.e., unusual stopping of the menstrual period).
• To help a pregnancy occur during egg donor or infertility procedures in females who do not produce enough progesterone.
• To prevent oestrogen from thickening the lining of the uterus (a condition known as endometrial hyperplasia).
• To treat pain that is related to endometriosis (a condition where the endometrial tissue which lines the uterus becomes displaced in other female organs).
• To treat heavy bleeding of the uterus (known as dysfunctional uterine bleeding) by starting or stopping the menstrual cycle.
• To test the body’s production of certain hormones like oestrogen.
• To treat other conditions, such as loss of appetite and severe weight or muscle loss in patients with acquired immunodeficiency syndrome (AIDS) or cancer by causing certain proteins to be produced that cause increased appetite and weight gain.

9. What is the difference between progesterone and progestin?

Although progestin is used to mimic the effects of the hormone progesterone, here are some differences between these two hormones:

9.1. On the Basis of Occurrence

Progesterone, produced by the corpus luteum, occurs naturally in the body. It regulates the menstrual cycle, supports pregnancy, and maintains the uterine lining or endometrium.

Progestin, on the other hand, is an artificial synthetic compound and is used to mimic the effects of progesterone in the body.

9.2. On the Basis of Medical Uses

Progesterone is used for the purposes of hormone replacement therapy (HRT), and assisted reproductive technology (ART), and is also found in certain contraceptives.

Progestin has a diverse range of medical applications, such as, birth control pills, hormone replacement therapy, treatment of menstrual disorders, and as part of hormone therapy for transgender individuals. This artificial synthetic hormone is also found in certain types of long-acting contraception, such as intrauterine devices (IUDs) and contraceptive implants.

9.3. On the Basis of Bioavailability

Progesterone, which is a natural hormone, is available in several forms, such as oral capsules, creams, gels, and injections. If you take this hormone orally, it may have lower bioavailability; this is because progesterone undergoes extensive metabolism in the liver.

Progestin, the synthetic hormone, is also available in various forms, such as, oral pills, injections, patches, and it is even found in intrauterine devices or IUDs. Compared to the natural hormone progesterone, progestin is designed to have improved bioavailability as well as stability.

9.4. On the Basis of Side Effects

Progesterone being a natural hormone has fewer side effects compared to certain progestins. Yet, it may cause some side effects. Side effects of this natural hormone include drowsiness, breast tenderness, and changes in menstrual patterns.

Progestin, on the other hand, has varying side effects that depend on the specific compounds used as well as the method of administration. Some side effects that you may experience with this synthetic substitute for progesterone are weight gain, mood changes, breast tenderness, and irregular bleeding, especially when used in birth control pills.

9.5. On the Basis of Use in Birth Control

Progesterone is not usually used to serve the purpose of a standalone contraceptive. Instead, it is often combined with another hormone estrogen in birth control pills in order to create a combined oral contraceptive.

Progestin, on the other hand is a key component in many birth control pills. These include progestin-only pills (also popularly referred to as the “mini-pill“), hormonal IUDs, contraceptive implants, and some types of contraceptive injections.

10. Conclusion

It is important to maintain normal progesterone levels in the body for the overall health of your reproductive system, bone health, and neuroprotection. Trying to avoid and treat hormonal imbalances is a good way to make sure progesterone levels in the body stay normal. With the right lifestyle and dietary changes accompanied by medical help and regular monitoring, keeping your progesterone levels normal would be really easy.

Last Updated on December 23, 2023 by soubhik92@gmail.com