Synthetic Hormones in Birth Control: Why We Use Them and Other Options

Nearly every time I open Instagram, someone has sent me a post of an influencer talking about the challenges they’ve faced from hormonal birth control, and why the synthetic hormones in birth control are horrible for our bodies. I get it. I tried out four different versions of the pill before I found one that worked, and ultimately said “Eff this” and switched to an IUD. Finding the right birth control SUCKS. It’s an underresearched domain, and when we have side effects, we’re just expected to suck it up, because it’s better than an unwanted pregnancy or terrible PMS.

However, I don’t vibe with the take that all of these side effects are the result of synthetic hormones in birth control — hormones are incredibly complex, and whether or not they’re synthetic is less important than how they function. Today, I’m going to explain why we use synthetic hormones in birth control, what other options are out there, and what the future of hormonal birth control looks like.

I also recognize that while hormonal birth control works incredibly well for some people, it doesn’t work well for others. I’m not getting into non-hormonal birth control methods here, but will absolutely address the research on that front sometime soon.

As a bit of a warning: there is hella chemistry in this post. I’m gonna do my absolute best to break it down for y’all so it’s easy to understand how synthetic hormones in birth control work and how natural hormones would work differently. (Tbh, I would be highly skeptical of anyone who wanted to discuss the benefits/disadvantages of hormonal birth control WITHOUT talking about how these drugs actually work.)

Girls Love Evidence is a biochemistry-friendly zone, and we don’t demonize things based on how big their chemical names are or if they’re “synthetic”, but rather on what actually happens to people who take them.

What is a natural hormone and what is a synthetic hormone?

When we talk about natural hormones, this is in reference to a hormone produced from a natural product. They could come from a plant or an animal, and some natural hormones occur in foods — such as phytoestrogens in soybeans or flax seeds. While these hormones aren’t created in labs, they are generally still processed in labs so that they can be used by humans.

Another class of hormone that we see commonly referred to as “natural” should technically be called bioidentical hormonesBioidentical means that the hormone is exactly the same as the hormones that are produced by your body.

According to the FDA (and the general scientific consensus), natural and bioidentical hormones aren’t any safer or more effective than synthetic hormones.

Why are there synthetic hormones in birth control?

Synthetic hormones in birth control are far more common than natural (or bioidentical) hormones. This is because the two hormones in birth control, progesterone and estrogen, are super hard to extract from a plant or animal source and turn into medicine.

This is because progesterone and estrogen are fatty molecules. If you tried to take them in their natural form, they wouldn’t enter the bloodstream and would instead stay stuck to fatty tissues in the intestines. Think about oil separating in water— if you pour more oil into an oil/water mixture, the new oil just clumps with the oil that is already there.

To get around this, chemists created progestins that had more hydrophilic (water-loving) properties, so they would enter the bloodstream rather than stick to the intestines.

The differences between synthetic hormones in birth control and natural hormones

In short, there are two main types of birth control pills: combination pills (estrogen/progestin) and progestin-only pills. They work by stopping ovulation, so sperm can’t meet an egg.

While there are few different progestins used in birth control pills, nearly all birth control pills that contain a synthetic estrogen contain the same one: Ethinyl estradiol. It’s been approved by the FDA since 1943, and while the dose of Ethinyl estradiol has changed over time, it’s still the same chemical.

When Ethinyl estradiol enters the body, it is able to work on the same receptors in the body as the estrogens that are already in the body (called endogenous estrogen), and prevents the body from releasing an egg. It doesn’t look exactly the same as endogenous estrogen, but it works in basically the same way.

Endogenous estrogen on the left, versus Ethinyl estradiol on the right.

Only one birth control pill is available in the U.S. that contains estrogen that looks the same as our endogenous estrogen. The pill, called Natazia (Estradiol valerate), is synthetic but turns into a bioidentical estrogen once it’s inside the body. (Yes, this is very cool, and science is awesome.)

Estradiol valerate looks like the left figure when it enters the body, but as soon as it is absorbed by the body, it releases 17β-Estradiol, a bioidentical estrogen. (The circled red part at left is “cleaved” to become the OH group).

While we don’t know for sure if bioidentical estrogens are any safer or more effective than synthetic estrogens, a recent study from a Finnish team found that pills containing estradiol valerate may have some advantages over ethinyl estradiol. While the bioidentical form had no significant effect on inflammation and lipids, those taking the synthetic estrogen had increased CRP and PTX-3 (markers of inflammation), as well as higher HDL and triglycerides. While, with only 59 participants over 9 weeks, this is definitely not sufficient to say “synthetic bad”, it should definitely spark interest for people concerned about the impact of synthetic hormones.

The future of birth control

Birth control pills have gone through multiple iterations since first being approved in 1960. However, the actual hormones in them haven’t changed much. While over time, dosage of hormones within the pill has decreased, estrogen and progestin have remained the primary hormones used.

Most of the estrogens currently in use were developed over 50 years ago, and the most recent progestins were approved about 15 years ago. Considering nearly 11 million Americans are on the pill, it’s been an area with little innovation.

But as of about a month ago, a new estrogen birth control pill has entered the market. The pill, called Nextstellis, contains estetrol, an estrogen that has been produced from a plant source. It has similar efficacy data to other forms of the pill (~98% effective), and it worked similarly for varying people with varying BMIs (good news!!!).

Since we’ll probably never have a ‘one size fits all birth control option, the fact that there is development in the field is a good sign. There’s no need to panic about synthetic hormones in birth control — they are perfectly safe for most people. However, since (at least in theory) the entire idea of medicine and science is to improve our lives, we should use research and science to reduce side effects and better our health.

synthetic hormones in birth control, explaining the science