Content table
If you’re TTC, you may be tracking your hormones to know when to get busy with your partner. And luteinizing hormone (LH) and estrogen are two to watch for. LH surges around mid-cycle, which triggers ovulation. Knowing when that happens is important if you want sperm to greet an egg!
Typically, estrogen rises right before LH spikes. This thickens the uterine lining, so your womb is ready for a fertilized egg to implant. But does estrogen always rise before ovulation?
In this article, we’ll cover what hormone really causes the LH surge along with estrogen’s role in pregnancy.
But to understand better, let’s first do a refresh on your menstrual cycle.
Menstrual cycle basics
Each month, your hormones rise and fall in a delicate dance. They interact in a feedback loop, triggering changes in your cycle.
Your menstrual cycle has two phases: the follicular phase and the luteal phase.
Follicular phase
This is the first half of your menstrual cycle. It starts the first day of your period and ends when you ovulate. Menstruation is part of your follicular phase.
Estrogen is the dominant hormone during this phase, particularly estradiol. This is the form of estrogen your ovarian follicles produce. But for estrogen to rise, it needs the help of follicle stimulating hormone (FSH).
Aptly named, FSH stimulates a batch of follicles to develop. Follicles are fluid-filled sacs that house an immature egg. As these follicles grow, they produce estrogen. And as estrogen rises, the uterine wall thickens to prepare for a potential pregnancy.
Typically, one follicle develops more quickly than the others. This is known as the dominant follicle. The dominant follicle keeps maturing and secretes more estrogen.
Estrogen levels hit their peak about three-four days before ovulation. Once estrogen levels are high, the pituitary gland gets the signal to reduce FSH. This causes the remaining follicles to break down, while the dominant follicle keeps growing.
High estrogen levels also tell your pituitary gland to ramp up luteinizing hormone. LH begins to rise about 24-36 hours before ovulation, peaking around 8-20 hours before an egg is released. This rapid rise in LH triggers ovulation.
The luteal phase
This is the second half of your menstrual cycle or the time between ovulation and the start of your next period. During this phase, the spotlight shifts from estrogen to progesterone.
The empty follicle that releases the egg transforms into a temporary organ called the corpus luteum. The corpus luteum then begins secreting progesterone. This nourishes the lining of your uterus to get it ready for a fertilized egg to implant.
If sperm fertilizes the egg and it attaches to your uterus, voila! You become pregnant. If fertilization doesn’t happen, progesterone drops. This causes your uterine lining to shed, triggering the start of your period.
Can LH surge without a rise in estrogen?
Research suggests it’s possible.
For example, one study had ten women take letrozole, a drug that lowers estrogen levels. Even though estrogen levels were lower, all ten women ovulated. Without an LH surge, ovulation isn’t possible. This means these women had an LH surge despite having lower estrogen.
Another study did the opposite. It gave estrogen to subjects in their follicular phase to see how it affected ovulation. They then compared these women’s LH surges to healthy women with spontaneous surges.
They found women with spontaneous surges had a greater LH response than those who took estrogen. This suggests estrogen isn’t the hormone triggering the LH surge.
So which hormone causes an LH surge?
That honor goes to gonadotropin-releasing hormone (GnRH). GnRH is a hormone released by the hypothalamus in your brain. It stimulates your pituitary gland to secrete follicle stimulating hormone (FSH) and luteinizing hormone (LH).
But it’s not that simple. Estrogen has a strong feedback loop with the hypothalamus to regulate GnRH. During most of your reproductive cycle, the feedback loop is negative. This reduces GnRH, which prevents LH from surging.
Once estrogen levels are high and the uterine lining is thick enough to welcome an egg, the feedback loop switches to positive. This causes GnRH to rise, which triggers a surge in LH.
One study put the importance of GnRH in the surge to the test. It gave subjects a GnRH antagonist (a drug that blocks GnRH) before and during an LH surge. They found it either disrupted the surge or significantly reduced LH levels.
This suggests GnRH is crucial to start and maintain an LH surge. So, while estrogen may play a role in the surge, it doesn’t do it alone.
What happens if I don’t have an estrogen surge before my LH surge?
Without a rise in estrogen, your womb won’t be ready for pregnancy. Remember, estrogen’s rise in the follicular phase helps thicken the endometrium. This gets your uterus ready for an egg to attach.
But estrogen is also important for ovulation. Once estrogen is high, it signals the pituitary to bump up GnRH. As GnRH rises, it triggers the LH surge. If your estrogen levels don’t rise enough in the follicular phase, your ovaries may not release an egg.
While you need estrogen to get pregnant, its rise may not always be high enough to be apparent on the test. If this is the case for you, keep testing and tracking your estrogen and LH. This will help you understand your cycles better. If you have any concerns about your estrogen levels, check in with your doctor.
How can I tell I ovulated after an LH surge without an estrogen surge?
In short? Progesterone.
After you ovulate, the follicle that held the egg forms the corpus luteum that secretes progesterone. This nourishes the endometrium to get it thick enough for a fertilized egg to implant.
You can use the Inito Fertility Monitor to confirm you ovulated. Inito measures PdG, a metabolite of progesterone, in your urine to confirm ovulation. But it also tracks LH, FSH, and estrogen to give you a complete picture of your fertile window.
Can I get pregnant if my estrogen doesn’t rise before an LH surge?
As long as you ovulate, you can get pregnant! That said, to maintain pregnancy, your body needs the right balance of hormones. This includes adequate estrogen levels.
Estrogen helps the uterus expand to make room for your growing baby. It also helps your baby’s organs develop, including the placenta.
If your estrogen levels are too low, you face a higher risk of negative pregnancy outcomes. This includes miscarriage and a lower live birth rate.
If you’re TTC and are concerned you may have low estrogen, speak with your doctor. They can help you figure out what’s causing your low estrogen and provide supplements if needed.
Read More: Healthy Estrogen Levels for Pregnancy: Why It’s Important
Causes of low estrogen and high LH
Here are a few ways a low estrogen and high LH imbalance can happen:
- Menopause
Menopause marks the end of your reproductive years. During the menopausal transition hormone production changes dramatically. Estrogen falls and you become less responsive to LH and FSH, causing your body to produce more of these hormones. This can lead to low estrogen and high FSH and LH levels.
- Primary ovarian insufficiency (POI)
Also known as premature ovulation failure, this is when your ovaries stop producing eggs before age 40. This is usually due to problems with the ovarian follicles. Since your follicles make estrogen, this can lead to low estrogen levels.
- Polycystic ovary syndrome (PCOS)
This hormonal imbalance causes high levels of androgens (male hormones). Women with PCOS often have high LH levels too. Yet PCOS can affect other hormones as well, including estrogen. Some research suggests women with PCOS may have steady estrogen levels, without the mid-follicular rise.
- Pituitary gland disorders
Your pituitary gland stimulates your ovaries to produce estrogen. So when this gland is not working properly, your estrogen levels may suffer.
Learn More: Low Estrogen: What It Means & Why It Matters
Frequently asked questions
On which day does the LH surge occur?
That depends on your cycle length. Ovulation usually happens 12-14 days before you start your period. As mentioned, the LH surge starts around 36 hours before ovulation and peaks 8-20 hours before.
So let’s say you have a 28-day cycle. If you ovulate on day 14, your LH surge would start a day or two before that (day 12 or 13).
Can you have regular periods but no LH surge?
Yep. Well, you may seem to have regular periods at least. If you don’t have an LH surge, you can’t ovulate. This is known as anovulation, and it’s the leading cause of infertility.
Progesterone is in charge of keeping your periods regular. If your ovaries don’t release an egg, your progesterone levels stay low. This can lead to breakthrough or withdrawal bleeding, which may be considered your period.
Read More: Can I Have My Periods & Not Ovulate?
Can LH rise without a rise in estrogen?
Yes, some studies suggest LH can surge without a significant rise in estrogen. Yet it’s not clear how. More research is needed to better understand.
I had egg-white cervical mucus, but no LH surge. What gives?
Estrogen helps your body make that slippery cervical mucus that shows up before you ovulate This makes sperm swim easier as they search for an egg.
If you’ve noticed cervical mucus that resembles egg whites on your underwear, it means your estrogen started rising. Either you tested too soon, and your LH surge is on its way – or you may have had an anovulatory cycle.
It’s also possible you used an ovulation predictor kit (OPK) that wasn’t sensitive enough to detect your LH surge. You can use Inito to prevent this.
Wrapping it up
Having an LH surge without a significant rise in estrogen is normal for the most part unless proved otherwise.
If you’re ovulating and having regular periods, without any signs of low estrogen (i.e. tender breasts, moodiness, dry skin, vaginal dryness), you’re good. If you do have signs of low estrogen, consult with your doctor. They can help you figure out what’s behind your LH surge without an apparent estrogen surge.
Takeaways
- Estrogen typically rises about 3-4 days before ovulation.
- High estrogen levels tell the hypothalamus to secrete GnRH. As GnRH levels rise, it causes the luteinizing hormone to surge.
- LH is the hormone that triggers ovulation. It starts rising about 24-36 hours before ovulation, causing the egg to break free from the follicle.
- Some research suggests LH surges can happen even if estrogen levels are low.
- Other studies show that if GnRH is blocked, it causes problems initiating or sustaining the LH surge.
- While ovulation is possible without a huge rise in estrogen, low estrogen makes pregnancy difficult to maintain.
- Estrogen enlarges your uterus, so there’s space for a growing baby. It also helps your baby’s organs develop.
- Low estrogen levels can be due to menopause, PCOS, primary ovarian insufficiency, or pituitary problems.
- You can track your fertile window with the Inito Fertility Monitor. Inito also measures PdG, a urine metabolite of progesterone, to confirm ovulation.
Was this article helpful?
- Physiology, Menstrual Cycle – StatPearls – NCBI Bookshelf
- The Normal Menstrual Cycle and the Control of Ovulation – Endotext – NCBI Bookshelf
- Sustained elevated estradiol is not the trigger for the LH surge. All women ovulate when letrozole is administered throughout the cycle: a prospective controlled study of normally ovulating women – Fertility and Sterility
- The Neurobiology of Preovulatory and Estradiol-Induced Gonadotropin-Releasing Hormone Surges – PMC
- Effect of gonadotrophin‐releasing hormone (GnRH) antagonist during the LH surge in normal women and during controlled ovarian hyperstimulation – Christin‐Maitre – 2000 – Clinical Endocrinology – Wiley Online Library
- Plasma immunoreactive estrogens and LH during the menstrual cycle
- Ovulation detection in the human
- The impact of estradiol on pregnancy outcomes in letrozole-stimulated frozen embryo transfer cycles – PMC
- How do healthcare providers diagnose menopause? | NICHD
- The Polycystic Ovary Syndrome: An update on metabolic and hormonal mechanisms – PMC
