What’s the difference between estriol vs. estradiol? These 2 are forms of estrogen, a female hormone. Both forms are natural steroid hormones present in your body. Both of these hormones are good for HRT (hormone replacement therapy) in post-menopausal women. They are not the only estrogen forms. There is a third form called estrone. Estrone is termed E1 while estradiol and estriol are termed E2 and E3 respectively. Estrone is usually produced during menarche (a girl’s first period) and menopause. You won’t find estrone is any HRT. Experts consider it to be too weak to exert any therapeutic effects. Estradiol and estriol, on the other hand, are used for HRT. The receptors for E2 and E3 are found in the breast tissue, uterus lining, and ovaries, as well as in the brain, kidneys, heart, lungs, and bones.
They are both estrogens, but estradiol (E2) and estriol (E3) are different. E3 is weaker than E2. That’s why you can only find it in compounded hormonal therapy products. E2 has a higher potency. The FDA approves it for HRT. So we can say that estradiol is a much stronger estrogen form and, as such, more effective. Because estriol is weaker, it might be safer than estradiol. But we might need more clinical trials to confirm its safety and effectiveness.
Estriol vs. Estradiol: What’s The Difference?
E3 naturally increases during pregnancy. This form is approved by the FDA for treating urinary incontinence. Vet doctors usually prescribe it for female dogs. It is most often prescribed after the removal of a dog’s uterus and ovaries.
The FDA does not, however, approve Estriol for use in humans. However, certain compounding pharmacies might compound estriol with some other drugs and sell it.
Estradiol, on the other hand, is very potent. It is more potent than any of the other estrogen forms. You will often find estradiol in low-dose contraceptive pills. These are used by women of child-bearing age to prevent pregnancy.
Estradiol is available as tablets, patches, or creams. You can also find it in some FDA-approved products. These include trade names like Estrace, Vagifem, Climara, and Vivelle-Dot, among others. That’s not all. The FDA also approves E2 in bio-identical hormone therapy that includes progesterone.
The most common use of Estrogen generally is for HRT in women that have menopause symptoms. But as we mentioned earlier, you will often find estrogen with progesterone (or progestins) in HRT treatments. The bottom line here is this. Remember that there are many other female hormones aside from estrogen.
Estradiol is the estrogen form that the FDA approves for treating menopause symptoms. Some of these symptoms are as follows:
- Hot flashes
- Night sweats
- Other vasomotor symptoms
- Vaginal dryness
- Vaginal atrophy
- Thinning out
Estradiol also works well for managing late-stage cancer of the breast. This is especially so for one that has metastasized. Note that it does not cure cancer. It only reduces its severity. So we can call it palliative care alone.
But then, estradiol can also contribute to therapy for ER-positive breast cancer (metastasized) and androgen-dependent prostate cancer (advanced stage). So you see that it can also function as a palliative care option for some men.
Estriol, on the other hand, does not have the FDA’s approval for use in humans. It is only approved for treating female dogs. And even for that, the only approved form is Incurin.
Which Form is More Effective?
Of the 3 estrogen forms, estradiol has more potency. It is the only one that the FDA approved for treating estrogen-related issues in humans. Estriol (E3), on the other hand, as well as estrone (E2), has no such approval in America. But then, you can sometimes find E1 and E3 in compounded medications.
Estradiol, which is the most potent and most common, is mostly used for post-menopause HRT. Unlike estriol, all estradiol forms are approved to be used for HRT. And they are available in various formats.
There hasn’t been any head-to-head trial to compare estriol with estradiol. But some studies have proven the effectiveness and safety of estriol for menopause symptoms. If you apply it topically, it can help treat vaginal atrophy, especially when other drugs are added with it.
Because estriol has less potency, however, it might have milder adverse effects. But that does not rule out any of the side effects. Just that they may be milder and the risks may be lesser. Estriol, just like every other estrogen therapy has risks associated with endometrial cancer, breast cancer, and endometrial hyperplasia.
Adverse Effects of E2 and E3 Estrogen
The most rampant side effects people suffer from estrogen therapy are as follows:
- Menstrual changes (your bleeding patterns might change)
- Painful menstruation or dysmenorrhea
- Breast tenderness
Other adverse effects of oral and topical estrogens include:
- Hair loss
- Weight gain
But then, some other direct effects may occur when you apply topical E2 or E3 to your vagina. These include:
- Increased secretions
- Fungal infections (or candidiasis) in severe cases
Estrogen (both E2 and E3) can increase melanin production. This can, in turn, increase pigmentation and darken your skin. But this does not happen in all cases.
Those are still mild side effects. Some side effects could be more severe. They include:
- High BP or hypertension
- Aggravates Asthma
- Heart attack
- Gallbladder disease
- Blood clots (or thromboembolism)
- Low calcium
- Enlargement of uterine fibroids
- Higher risks of cervical and breast cancer.
More so, certain drugs can inhibit the enzymes that metabolize estrogen. Such drugs will hinder the elimination of estrogen from your body. As such, the risks of having side effects would increase. Such drugs include:
- Some antibiotics
The estrogen hormones can also react chemically with certain compounds in grapefruit juice. You should, therefore, avoid grapefruit juice if you’re on estriol or estrogen therapy.
Well, estriol vs. estradiol is not a hard nut to crack. You are not likely to have any problem with not knowing their difference if you avoid self-medication and follow your doctor’s instructions always.