LH Explained: Luteinizing Hormone Function

Get ready to learn the role luteinizing hormone plays in our reproductive health. Join us on a journey of all things ovulatory as we answer the question ‘what is luteinizing hormone?’ We’ll reveal how measuring luteinizing hormone can help you both plan and prevent pregnancy, as well as the best time to measure LH.

Stylized white text with the letters L and H against a purple background.

What is LH?

LH stands for luteinizing hormone. It’s a bit of a tongue twister, but this hormone plays an important part in both the male and female reproductive systems. For men, LH is involved in releasing the sex hormone testosterone and aids with the production of sperm. For women, LH is regulated by the estrogen hormone and plays a crucial role in the menstrual cycle

When we think about female sex hormones, we’re probably thinking about the uterus. However, as like all great things, ovulation starts in the brain. LH is formed in the pituitary gland, binding with receptors in the hypothalamus before it’s released into the bloodstream. It then makes its way to the ovaries. LH is always present in the body, but a rise in estrogen causes a spike in luteinizing hormone, which triggers ovulation (the release of a female egg cell from an ovary). 

When to measure LH

Ovulation happens at the end of the follicular phase in the menstrual cycle, but unless you know your predicted fertile window, it can be hard to know when to measure for the presence of luteinizing hormone.  If you take an ovulation test, LH levels can usually be detected between 24-48 hours before ovulation. 

Historically, the medical stance on ovulation was that it occurs around day 14 in the cycle. However, this calculation is based on the myth of the 28-day cycle, we now know that cycle lengths vary, so detecting ovulation will be easier if you understand the changes and length of your own menstrual cycle.

How do ovulation tests work? 

Ovulation tests or LH tests work by measuring the concentration of luteinizing hormone in urine. If LH levels are strong, as indicated on the test strip, it could mean ovulation is approaching. It’s worth knowing that while you might test positive for a surge in LH, an ovulation test is not a guarantee that ovulation will actually occur, it’s more of an indication that it is going to happen. 

If you want to get hold of a test kit, you can find ovulation tests in your pharmacy, or you can order ovulation tests online from our webshop. Make sure you read the manufacturer’s instructions before use. It’s also possible to test LH through blood tests, but if you have concerns about your fertility, we always recommend you speak to your doctor. Read more on how and when to measure LH.

Luteinizing hormone levels: low or high

So we now understand what luteinizing hormone is, and that it plays a pivotal part in our menstrual cycles. But what happens when there’s an imbalance of LH? Well, too much luteinizing hormone can result in infertility and in some cases also polycystic ovary syndrome (PCOS). Of course, if you have concerns about either of these, you should consult a healthcare professional.

Similarly, too little luteinizing hormone can also indicate infertility as the required amount of hormone to stimulate ovulation isn’t present. Many forms of fertility treatment involve regulating the levels of LH - alongside other hormones - to increase fertility. It’s important to remember that all of our bodies are different and react in different ways. A low reading of luteinizing hormone in men can also have an impact on fertility, as LH is required for sperm production. 

Luteinizing hormone and pregnancy

For those planning a pregnancy, it’s useful to understand the hormones at play and how they will change during gestation. Since luteinizing hormone is a hormone that works to regulate the phases of the menstrual cycle, there is no surge of LH during pregnancy. However, the sex hormones progesterone and estrogen play a key role in fetal development and getting the body ready for giving birth. 

How does Natural Cycles measure LH? 

First things first, measuring luteinizing hormone is an optional part of using Natural Cycles. This digital birth control method works by pairing the basal body temperature method with an algorithm that learns your unique cycle. While using Natural Cycles, you have the option to give the algorithm a boost by taking ovulation tests, and you can input positive or negative test results directly into the app - these results can help the algorithm find your ovulation faster. We have recently added an LH Guide to the app so you can learn more about how ovulation tests work and how they help the algorithm find your fertile days.

We hope you’ve learned something about the wonders of luteinizing hormone and its role in your reproductive health! If you’re interested in finding out more about your ovulation, why not try Natural Cycles? It’s FDA Cleared, 100% hormone-free and personalized to your unique cycle.

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Written By

Jennifer Gray

A writer with a passion for women’s health, Jennifer Gray has years of experience writing about various reproductive health topics including birth control, planning pregnancy, women’s anatomy, and so much more.

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Scientifically Reviewed

Jack Pearson

With 10 years of experience working in the field of fertility, Dr. Jack Pearson is Natural Cycles’ in-house expert. As Medical Affairs Manager, he dedicates his time to conducting groundbreaking research and educating healthcare professionals.

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