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There is a common misperception about progesterone (naturally occurring hormone) and progestin (the synthetic version) — namely that they are essentially identical. “Progesterone” and “progestin” are used interchangeably so often that patients may inadvertently think of them as one and the same, and put themselves at risk for health issues by not being aware that they are not, in fact, synonymous. So what is the difference between progesterone and progestin? The answer may surprise you. What is progesterone?

Progesterone is a naturally occurring hormone that functions primarily to regulate reproductive processes. It is produced by the adrenal glands and ovaries or testes, and by the placenta in pregnant women. In women, progesterone is responsible for preparing the uterus for the implantation of an egg and maintaining the lining of the uterus — the endometrium — during pregnancy.

In addition to providing reproductive support, progesterone has other benefits, including:

  • Helping to protect against the development of fibrocystic breast tissue — and may help protect against developing certain types of breast cancer.

  • Decreasing the risk of developing ovarian and uterine cancers by balancing estrogen.

  • Helping to normalize blood clotting

  • Being a coronary vasodilator.

  • Restoring libido.

  • Balancing estrogen and testosterone.

  • Improving brain metabolism by boosting the function of mitochondria.

What is progestin? Progestin is a general-use term to describe a synthetic analog that closely resembles progesterone and is used to perform similar functions as progesterone. However, progestins' have been modified at a cellular level — primarily to ensure patentability — and are not bioidentical to naturally occurring progesterone. In fact, progestins' are structurally different from progesterone and more closely resemble testosterone. Progestins are used widely in contraceptive pills/injections/IUDs, fertility drugs, and hormone replacement drugs. Despite the prevalence of their use, progestins' have many side effects, including:

  • Causing menstrual irregularities, such as amenorrhea (the absence of regular menstruation) or menorrhagia (excessive or prolonged bleeding during menstruation).

  • Increasing the risk of development of breast cancer than the use of estrogen alone – a 16,608 women trial involving women who had a full hysterectomy showed increased rates of developing breast cancer when taking progestin with estrogen (1 in 12) vs estrogen alone (1 in 99) at 2 years of use (1).

  • Causing migraine headaches (2).

  • Decreasing bone density.

  • Increased risk of thrombotic disorders, like deep vein thrombosis and blood clots.

  • Increased body fat % during use (3).

  • Increasing the risk of the development of dementia.

What are progestins used for and why are they used so often? Progestins are generally prescribed as part of a contraceptive or hormone replacement regimen. Progestins are used instead of progesterone because progesterone is not a contraceptive hormone. Progestin impedes or inhibits the body’s ability to ovulate, and hence become pregnant. Progestin-only contraception, such as the mini-pill or an implant, prevents the ovaries from releasing an egg and thickens the mucus at the opening of the cervix which prevents sperm from entering the uterus. Women may require hormone replacement therapy for a number of reasons, including hysterectomy or menopause. When the ovaries no longer produce estrogen, hormone replacement therapy is often recommended to ease menopausal symptoms. However, estrogen-only hormone therapy increases the risk of the development of increased abnormal endometrial growth, so a combination of estrogen and progestin is often used. Progesterone or progestin — what you need to know Structurally, progesterone and progestin are completely different. In fact, there is a growing body of evidence that progestins do not always act like progesterone and do not always affect the targeted tissues the way progesterone would. While progestin may behave similarly to progesterone, progestin reacts differently with the progesterone receptors in the body. If you are experiencing a progesterone deficiency and are in need of hormone replacement therapy, your better option may be to use bioidentical progesterone. Bioidentical estrogen and progesterone may pose lowers risks of developing breast cancer than their synthetic counterparts (4). Bioidentical progesterone is lab-made but is an exact copy of the body’s naturally occurring progesterone. If you wish to discuss hormone replacement therapy options further, it's best to speak with a licensed professional who is able to prescribe bioidentical hormones. Please feel free to contact Toronto Naturopathic Doctor, Dr. Courtney Holmberg at 647-351-7282 to schedule a consultation today! References:





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