Progesterone
What is Progesterone?
Progesterone USP is prescribed by physicians to supplement a woman’s natural
production of the hormone. USP stands for United States Pharmacopoeia, which is the national standard of purity for substances used in the manufacture of drugs and cosmetics. Natural progesterone USP simply confirms that the progesterone is identical to the progesterone produced by the human body, not the synthetic version generally referred to as progestin.
First isolated in 1934, progesterone USP is a white or creamy white crystalline powder, is odorless, stable in the air, and is nearly insoluble in water. These natural hormones, derived from wild yam or soy, are bioidentical to what your body produces so they act in the same way.
"Micronized" progesterone is progesterone USP, the natural form of progesterone, broken down into very tiny particles. The process of micronization allows for steady, even absorption of the medication. In this country, the Upjohn Company sells micronized progesterone as a bulk powder to pharmacies 
that specially prepare, or "compound," the powder into capsules or slow-release tablets in different doses as prescribed by physicians.
Progesterone vs Progestin
Natural or bioidentical progesterone USP should not be confused with synthetic progestin. Progestins are derivatives of progesterone used in medications like oral contraceptives or drugs like Provera®. While progestin’s chemical structure is only slightly different, its effects in the body can be very different from natural progesterone. For example, synthetic progestins can inhibit ovulation, thus suppressing the body’s output of it’s own natural progesterone. Synthetic progestin often intensifies rather than relieves PMS symptoms.
Forms of Administration
Natural progesterone USP is commonly prescribed for women experiencing symptoms of PMS, perimenopause, menopause, postpartum depression, and for pregnancy maintenance. Physicians prescribing natural progesterone have several dosage forms to choose between. Important considerations for physicians when choosing the appropriate dosage include:
Absorption characteristics – how much of the medication is absorbed, how fast, and how long it lasts
Symptom control and side effects
Ease of administration
Expense
Progesterone
The naturally occurring hormone progesterone means literally, "for gestation" – it is the hormone of pregnancy. Produced by the ovaries, progesterone prepares the lining of the uterus for the fertilized ovum and maintains pregnancy. Specifically, progesterone converts the womb lining into a soft spongy bed in order to enhance implantation of a fertilized egg. If implantation does not occur, progesterone levels fall and menstruation begins. Progesterone also affects contractions of the fallopian tubes, thickens the consistency of vaginal mucus, and raises body temperature slightly.
During a woman’s reproductive years, progesterone levels in the body fluctuate in a cyclic pattern. During the first half of the menstrual cycle, the concentration of progesterone in the bloodstream is less than 1 ng/ml. During the second half, or luteal phase, progesterone in the bloodstream ranges from 3 ng/ml to 25 ng/ml.
Very high levels of progesterone are necessary to maintain a pregnancy. When pregnancy occurs, the placenta takes over output of progesterone, producing levels up to 30 times greater than normal peak levels. Following birth, the progesterone level drops abruptly.
Women’s progesterone level naturally declines during perimenopause, and menopause, and after a hysterectomy, where the ovaries have been removed, as do her levels of estrogen and testosterone.
Progesterone and Estrogen Dominance
The balance of progesterone and estrogen in a woman’s body is very important. At different times in her life, hormonal imbalance can result in symptoms of PMS, perimenopause, or menopause. Symptoms of progesterone imbalance (referred to by Dr. Lee as estrogen dominance) include moodiness, hot flashes, night sweats, depression, weight gain, bloating, and breast tenderness.
Progesterone can:
Has a calming effect
Enhances mood
Regulates fluid balance
Normalizes sleep
Increases sex drive
Helps use fat for energy
Stabilizes blood sugar, thyroid function, and mineral balance
Decreases risk of endometrial cancer
May help protect against breast cancer, fibrocystic breasts, and osteoporosis