What's the difference between synthetic progestins and natural progesterone.

What's the difference between synthetic progestins and natural progesterone?

"Natural" progesterone (also termed USP Progesterone) refers to a single molecular structure that is "bio-identical" to the progesterone molecule that the body makes. Synthetic "progestins" or "progestogens," do not exactly duplicate the body's own progesterone molecule.
They mimic the body's progesterone closely enough to bind to progesterone receptor sites and have some progesterone-like effects, but they do not deliver the full range of "messages" that a natural progesterone molecule would. As such, synthetic progestins are not recommended for use during pregnancy; pregnancy requires progesterone. Synthetic progestins will not increase the serum or salivary levels of progesterone. In fact, synthetic progestins may cause a decrease in the body's levels of natural progesterone by blocking the process of progesterone production.
In contrast, research studies show that topical (skin) applications of natural progesterone may increase salivary and serum levels of progesterone.
What is USP Progesterone? United States Pharmacopoeia (USP) Progesterone simply means progesterone that exactly duplicates the progesterone naturally produced in the body, or "bio-identical" progesterone. The title "USP Progesterone" differentiates natural progesterone from synthetic progestins or progestogens.
What's the difference between wild yam and progesterone? Wild yam, Dioscorea barbasco, is an herb that has been used historically in herbal medicine for women's health. Some of the actions of wild yam include smooth muscle relaxation and a mild diuretic effect.
Contrary to some information provided by companies producing wild yam products, wild yam does not convert into progesterone in the body. This conversion can only occur in a laboratory setting. The body may absorb wild yam extract through the skin, which may in turn have some effect on menopausal symptoms, yet research on both oral and topical applications of wild yam extract demonstrate no change in progesterone levels in the body.
Does natural progesterone have any side effects? Progesterone binds with progesterone receptor sites in the brain and causes a calming effect on the central nervous system. In excessive amounts, progesterone may have a relaxing effect on the brain, and may cause drowsiness. In a very small group of women who are extremely sensitive, progesterone of any kind may aggravate hormonal headaches or PMS symptoms. There are no long-term adverse effects noted for supplemental progesterone in amounts that replicate physiological levels of progesterone in the body.
What's the difference between synthetic and natural estrogen? The body naturally produces three main forms of estrogen:
estrone (E1),
estradiol (E2),
and estriol (E3).
Estrone is converted from estradiol in the liver. Synthesized in the ovaries and metabolized in the liver, estradiol is the most physiologically active form of estrogen.
When taken orally, estradiol is converted into estrone in the small intestine. Estriol is the shortest-acting estrogen and has a weaker effect than estradiol and estrone. Estriol remains intact when supplemented orally, i.e. estriol is not converted into estrone, as is true with estradiol supplementation. Because estriol competes with estrone for receptor uptake when given in large or repeated doses, it may have an anti-estrogenic effect in selective tissues like the breasts or uterus.
Estriol doses must be increased up to three times the dose of estradiol to achieve similar effects (e.g. reducing hot flashes and vaginal dryness in menopausal women). In Europe and China, estriol is the preferred form of estrogen for HRT.
Many of the hormone replacement therapy and birth control pharmaceuticals in the U.S. contain estradiol, the strongest of the three forms of estrogen. Some of the estrogens produced in the United States exactly duplicate one of the three forms of estrogen produced in the body, estradiol, so technically they are "natural." Many physicians are now prescribing "Tri-est", or "Bi-est", names given to combinations of E1/E2/E3 and E2/E3 respectively.
With a physician's prescription, licensed pharmacists may compound these combinations of natural estrogens. Other estrogens available differ chiefly in the source of the estrogen, e.g. whether they were derived from animal or plant products, or synthesized chemically. Synthetic estrogens are estrogenic compounds that are not found naturally in the human body. There is some debate as to whether estrogen from the urine of horses is "natural", but most naturally minded physicians agree that the use of estrogens derived from horses is not a "natural" approach for humans.