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Which hormone spikes midway through your cycle and triggers ovulation?

Written by: Dr. Amy Beckley, PhD, Founder and Inventor of the Proov test the first and only FDA-cleared test to confirm successful ovulation at home.

Medically reviewed by: Dr. Aimee Eyvazzadeh, MD, MPH

Written on 11/3/20


If you’re trying to conceive, ovulation is a critical event in your cycle. Why? Because leading up to ovulation is when you are fertile and most likely to get pregnant! Knowing when ovulation is going to occur can increase your chances of conception. 

One of the ways to predict ovulation is by tracking the hormone which spikes midway through your cycle and triggers ovulation: luteinizing hormone (LH)!

What is luteinizing hormone?

Luteinizing hormone is produced and released by the pituitary gland. It is a reproductive hormone responsible for controlling the function of the ovaries in women. LH plays a role in sexual development and functionality. 

What does luteinizing hormone do?

During the first half of your cycle — the follicular phase — luteinizing hormone is responsible for stimulating the ovaries to produce estrogen. Then just before ovulation (often around day 14 of your cycle), a surge in LH levels causes a mature ovarian follicle to rupture and release an egg. So, an LH surge triggers ovulation!

hormone spikes midway through cycle and triggers ovulation
A surge in luteinizing hormone levels triggers ovulation in the middle of your cycle.

For the remaining two weeks of your cycle, also known as the luteal phase, LH stimulates the corpus luteum (or empty follicle) to produce progesterone. A long, healthy luteal phase is actually supported initially by elevated LH levels. Progesterone confirms ovulation and prepares the uterine lining to receive an embryo.

When exactly does luteinizing hormone surge?

As we mentioned, a luteinizing hormone surge occurs during the follicular phase, just before ovulation is going to occur. During this phase, estrogen is dominant and stimulates the pituitary gland to release LH. On average, an LH surge occurs about 24 hours before ovulation, although this can vary. Ovulation can occur anywhere between 16 to 48 hours after an LH surge. 

So if you ovulate on day 14 of your cycle, your LH levels should surge around day 12. But we know that this assumption is based on women who have 28-day cycles and the vast majority of women can actually have cycles that range anywhere from 22 to 36 days in length.

Since most women don’t ovulate exactly on day 14, it’s important to track your LH levels to ensure you catch the surge at the right time!

hormone spikes midway through cycle and triggers ovulation
On average, luteinizing hormone surges about 24 hours before ovulation occurs.

Why should I track luteinizing hormone levels?

Tracking luteinizing hormone levels is one of the most common ways to predict when ovulation is going to occur. The few days leading up to and day of ovulation — also known as your fertile window or peak fertility — are when intercourse is most likely to result in conception. If you’re trying to conceive, timing intercourse is critical to conception.

In fact, one study found that chances of conception are the highest on the day right before ovulation. This means that predicting ovulation with LH tracking before it actually occurs can increase your chances of conception. 

How do I track luteinizing hormone levels?

You can track luteinizing hormone levels with at-home LH test strips, also known as ovulation tests or ovulation predictor kits. While these tests are very common, they are often inaccurate for many women.

hormone spikes midway through cycle and triggers ovulation
Ovulation tests are 99% accurate at detecting luteinizing hormone levels in urine and help you identify the LH surge that opens your fertile window.

 

In fact, 1 in 10 women may never get a positive LH test for a variety of reasons. Some women may have LH surges that never reach the threshold that turns an LH test positive, while other women — such as those with PCOS — may have hormone imbalances that can prevent LH surges or cause irregular cycle patterns. 

If you never get a positive LH test or are wondering if LH tests are the right fit for you, we recommend consulting your doctor.

If I get a positive ovulation test, does that mean I ovulated?

Well, not exactly. Luteinizing hormone simply predicts when ovulation should occur, but doesn’t tell you if ovulation actually happened. In fact, anovulatory cycles — cycles where ovulation does not occur — can be common. One study found that about one-third of clinically normal cycles are anovulatory.

Women with PCOS also may experience anovulatory cycles. This is because they have a hormone imbalance that can cause luteinizing hormone to surge without actually triggering ovulation. 

So how do I confirm ovulation?

Remember our friend, progesterone? Luteinizing hormone stimulates the corpus luteum (empty follicle) to produce progesterone after ovulation has occurred. The presence of progesterone confirms ovulation. 

Since we’re talking urine-based tests, there’s another one that may interest you: PdG tests! PdG is the urine metabolite of progesterone and only rises after ovulation has occurred. Proov is the first and only FDA-cleared PdG test kit to confirm successful ovulation. 

hormone spikes midway through cycle and triggers ovulation
Proov is the first and only FDA-cleared PdG test kit to confirm successful ovulation.

Successful ovulation refers to an ovulatory event in which an egg was released and PdG levels remained elevated for long enough to allow for the best possible chance at conception. Positive Proov tests on days 7-10 after peak fertility (such as a positive LH test) confirms that successful ovulation did in fact occur.

Predicting and confirming ovulation

Predicting and confirming ovulation are important steps in any trying to conceive journey! Luckily with the new Proov Predict and Confirm kit, you can predict and confirm ovulation with just one box of test strips. 

hormone spikes midway through cycle and triggers ovulation
The new Proov Predict and Confirm kit allows you to predict and confirm ovulation with just one box of test strips.

Each Predict and Confirm kit comes with 15 LH tests and 5 PdG tests. You can start testing with the LH tests about 18 days before your next period is supposed to start. You get closer and closer to the day of suspected ovulation, you may want to test LH levels multiple times in one day as LH surges can be short. 

Once you get a positive LH test, you’ll then count 7 days and use the PdG tests on days 7, 8, 9, and 10 after peak fertility. As we mentioned, four positive tests during this window confirm that successful ovulation has in fact occurred.

Understanding luteinizing hormone and why you should measure it can help you achieve your fertility goals faster!