Progesterone is the main pro-gestational steroid hormone secreted by the female reproductive system. It is linked to the menstrual cycle, pregnancy, and development of an embryo. Progestin is an artificial form of progesterone that is used for medical purposes.

The ovaries, placenta, and adrenal glands produce progesterone to regulate the condition of the endometrium, which is the inner lining of the uterus.

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Progesterone is an important hormone in both men and women.

Progesterone is a steroid and a hormone. It has some important roles, particularly in the process of reproduction.

After puberty starts, the ovaries release a single egg each month. This process is called ovulation. The egg moves down the fallopian tube, and if it meets with sperm, it may be fertilized.

The corpus luteum is a temporary endocrine, or hormone-producing, gland that forms from the empty ovarian follicle after ovulation.

The corpus luteum becomes the main source of progesterone that is needed to maintain a pregnancy immediately after fertilization and implantation.

If fertilization does not occur, the corpus luteum breaks down, less progesterone is produced, and the levels of progesterone are too low to promote the growth of the uterine wall. As the lining of the womb is no longer maintained by progesterone from the corpus luteum, the lining breaks away, resulting in menstrual bleeding.

If conception occurs, progesterone stimulates the further development of blood vessels in the endometrium, and it stimulates glands in the endometrium to secrete nutrients that nourish the fertilized egg.

Progesterone prepares the tissue lining of the uterus to so that the fertilized egg can be implanted. Progesterone also helps to preserve the endometrium throughout pregnancy.

After conception, the placenta forms. The placenta begins to secrete progesterone to supplement, and surpass, the progesterone already secreted by the corpus luteum.

Levels of progesterone from the placenta remain high during pregnancy. This prevents other eggs from maturing, and it promotes changes in breast tissue to prepare for lactation.

If a woman does not ovulate, her ovaries do not produce progesterone. This is called an anovulatory cycle. Missed cycles often take place from the mid 30s onwards and become more frequent as menopause approaches.

Progesterone levels drop consistently just before the menopause. This is thought to be the major cause of symptoms experienced around the menopause.

Progesterone travels in the blood to tissues where there are progesterone receptors. It attaches to the receptors to produce actions in the body.

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Progesterone plays a key role during pregnancy.

Estrogen and progesterone are responsible for the release of an egg from the ovaries during ovulation.

Progesterone then:

  • Prepares the tissue lining of the uterus to allow the fertilized egg to implant
  • Maintains the endometrium throughout pregnancy
  • Prevents further egg release until a pregnancy has terminated
  • Prevents fertilization of more than one egg at a time, although more than one egg is occasionally released
  • Stops muscular contractions in the fallopian tubes once the egg has been transported
  • Plays an important role in fetal development during pregnancy
  • Stimulates the breast tissue to promote lactation and causes the glands to advance ready for producing milk
  • Strengthens the pelvic wall muscles in preparation for labor

In the case of a hormonal imbalance, an artificially produced version, progestin, may help.

Progesterone occurs naturally in the body, but laboratories can also produce it. Synthetic steroid hormones with progesterone-like properties are called progestin.

Progestin is available as capsules, in vaginal gels, implants, intrauterine devices (IUD), and injections.

Uses for progestin include treatment for:

Progestin side effects

Side effects of progestin use may include:

Uncommon but potentially serious side effects requiring medical attention include:

  • Breast lumps
  • Dimpling of breast skin
  • Clear or bloody discharge from nipple
  • Inverted nipple
  • Crusting or scaling of the nipple
  • Clay-colored stools
  • Migraine headache
  • Severe dizziness
  • Slow speech or difficulty speaking
  • Weakness or numbness of limbs
  • Absence of coordination
  • Breathlessness
  • Pounding heartbeat
  • Sharp chest pain
  • Coughing up blood
  • Leg swelling
  • Loss of or blurred vision
  • Bulging eyes
  • Double vision
  • Unexpected vaginal bleeding
  • Uncontrollable shaking hands
  • Seizures
  • Stomach pain or swelling
  • Depression
  • Hives, skin rash, and itching
  • Difficulty swallowing
  • Swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs
  • Hoarseness

Progestins are not suitable for people with a history of the following conditions, unless they are using it to treat the condition:

  • Liver tumors
  • Genital cancer
  • Breast cancer
  • Severe arterial disease
  • Undiagnosed vaginal bleeding
  • Acute porphyrias
  • Idiopathic jaundice
  • Severe pruritus occurring during pregnancy
  • Pemphigoid occurring during pregnancy

Birth control pills

Birth control pills, also known as oral contraceptives or hormonal contraceptives, make use of progesterone.

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Progestin is used in oral contraceptives.

Combination pills contain both estrogen and progestin.

They work by:

  • Preventing ovulation
  • Changing the lining of the womb to prevent a pregnancy from developing
  • Thickening the mucus at the cervix to prevent sperm from entering

Progestin-only hormonal methods include mini-pills, implants, and shots.

They:

  • Prevent the ovaries from releasing an egg
  • Thicken the mucus at the cervix to prevent sperm entering the uterus

The United States National Library of Medicine warn that cigarette smoking significantly increases the risk of serious side effects in those who use oral contraceptives. They advise smokers not to use oral contraceptives.

Hormone therapy

Hormone therapy (HT), previously known as hormone replacement therapy (HRT), helps to restore the balance of female hormones. HT can provide progesterone, estrogen, or a combination. It is available as a pill, nasal spray, patch, skin gel, injection, vaginal cream, or vaginal ring.

HT may relieve symptoms of perimenopause such as:

  • Hot flashes
  • Vaginal dryness
  • Pain with intercourse
  • Mood swings
  • Sleep disorders
  • Anxiety
  • Decreased sexual desire

In some women, estrogen leads to an overgrowth of the endometrium, or lining of the uterus. This can lead to endometrial cancer. A combined estrogen and progestin hormone therapy (HT) can prevent this.

However, HT can have adverse effects, and it increases the risk of some serious conditions.

The adverse effects of HT include:

  • Bloating
  • Breast soreness
  • Headaches
  • Mood swings
  • Nausea
  • Water retention

People who use HT have a higher risk of:

The FDA recommends using HT at the lowest possible dose for the shortest possible time needed to achieve treatment goals.

Women who use or are considering using hormone therapy should discuss the possible benefits and risks with their doctor.

Normal progesterone levels

Progesterone levels are relatively low before ovulation, and they usually increase when an egg is released from the ovary. Levels rise for several days and either continue to rise if pregnancy occurs, or they fall to initiate menstruation.

If progesterone levels do not increase and decrease monthly, this could indicate a problem with ovulation, menstruation, or both, and it may be a cause of infertility.

Women who experience a multiple pregnancy, meaning twins, triplets, and so on, typically have naturally higher levels of progesterone than those expecting one baby.

A blood test can be used to measure progesterone levels. The results can help determine the cause of infertility, track ovulation, help diagnose an ectopic or failing pregnancy, monitor pregnancy health, or assist in diagnosing abnormal uterine bleeding.

Why do progesterone levels fall?

Progesterone levels may fall because of:

  • Toxemia, or preeclampsia, late in pregnancy
  • Decreased function of ovaries
  • Amenorrhea
  • Ectopic pregnancy
  • Miscarriage

Why do progesterone levels rise?

Reasons for progesterone levels rising may include:

  • Ovarian cysts
  • Non-viable pregnancies
  • A rare form of ovarian cancer
  • Progesterone overproduction by the adrenal glands
  • Adrenal cancer
  • Congenital adrenal hyperplasia (CAH)

Progesterone is known as a female hormone, but males need progesterone to produce testosterone. The adrenal glands and testes in males produce progesterone.

Progesterone levels in males are similar to those of females in the follicular phase of the menstrual cycle, when the egg follicle on an ovary is preparing to release an egg.

Symptoms of low progesterone in males include:

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Low progesterone levels in men can lead to hair loss.
  • Low libido
  • Hair loss
  • Weight gain
  • Fatigue
  • Depression
  • Gynecomastia, which is breast development in males
  • Erectile dysfunction
  • Impotence
  • Bone loss
  • Muscle loss

Men with low progesterone levels have a higher risk of developing:

As males age, testosterone begins to decline, estrogen levels rise, and progesterone levels fall dramatically.