Luteinising hormone is an important cycling hormone, involved in the regulation of the menstrual cycle and ovulation. But what happens when our levels get a little off balance? In this article, we’ll explain exactly what luteinising hormone is, how it works, and take a deep dive into its importance for female fertility. We’ll also take a look at LH levels and why they’re important, as well as how to recognise the symptoms of low or high LH.

Quick facts:

• LH is a hormone that helps to regulate the menstrual cycle and trigger ovulation.
• A high LH level is commonly seen in people with PCOS or can be caused by certain lifestyle factors.
• A low LH level is commonly seen in people who have a problem with their pituitary gland—a common cause can be stress. 
• Low LH level can also be caused by diet and lifestyle factors.
• There are things you can do to promote healthy LH levels, including testing your hormones.

What is Luteinising Hormone (LH)? 

Luteinising hormone (LH) plays a huge role when it comes to fertility and ovulation, despite it being one of the lesser-known cycling hormones.

Luteinising hormone (LH) is what’s known as a gonadotropin hormone. There are only two types of this hormone, LH and its partner in crime, follicle-stimulating hormone (FSH).

Gonadotropins are hormones that are released from the pituitary gland in the brain, into the bloodstream where they are transported to the gonads—or ovaries in those assigned female-at-birth and the testes in those assigned male-at-birth.

LH has 3 main functions in those assigned-female-at-birth: 

• Stimulates the ovaries to produce oestrogen 
• Causes ovulation by surging at the midpoint in your cycle (around 2 weeks after the start of your period)
• It stimulates empty follicles in your ovaries to produce progesterone after ovulation, which helps to maintain a healthy pregnancy in the early weeks of gestation 

Oestrogen production

LH works in tandem with FSH to stimulate the ovaries and surrounding cells to produce oestrogen. First, LH stimulates what’s known as theca cells in the ovaries, which then produce testosterone.

Once testosterone is abundant, nearby granulosa cells are then stimulated by FSH to produce an enzyme called aromatase, which converts the testosterone into a type of oestrogen, oestradiol, or E2.

Without the correct functioning of LH or FSH, testosterone and oestrogen production can become impacted.

Ovulation

LH is also crucial for successful ovulation. First, FSH stimulates the growth of follicles (small sacs that contain your eggs) in your ovaries. A number of eggs mature during the first half of your cycle, but only one gets released during ovulation—usually the ‘most mature’ follicle.

In the days leading up to ovulation, this follicle increases its sensitivity to LH. It gradually produces more and more E2 and when this reaches a certain level, the pituitary gland releases a surge of LH.

This LH surge is what causes the follicle to rupture and release the mature egg into the fallopian tube—triggering ovulation.

Progesterone production

After ovulation has occurred, LH stimulates the now empty follicle to start producing progesterone throughout the second half of the menstrual cycle—also known as the luteal phase.

Both progesterone and E2 released by the empty follicle are intended to support conception, implantation and the early stages of pregnancy. However, if the egg is not fertilised and no embryo implants into the uterus, the empty follicle stops producing these hormones and eventually wastes away at the end of the menstrual cycle.

What are normal LH levels in women?

LH levels in women, or those assigned-female-at-birth, fluctuate during the menstrual cycle—so their levels will vary depending on where you are in your monthly cycle.

LH levels can also vary depending on an individual’s age and whether they’re pregnant.

Normal LH levels for women before menopause are around 5-25 IU/L, depending on the stage of the menstrual cycle. After menopause, normal LH levels range from around 14-52 IU/L.

LH levels during the menstrual cycle

Let’s take a closer look at how LH fluctuates during the menstrual cycle. As we mentioned earlier, a dramatic surge in LH around the middle of the cycle triggers ovulation.

But after ovulation, LH production is dulled by rising levels of progesterone. If no pregnancy occurs and progesterone levels fall, LH production will start again anew at the beginning of the next cycle.

LH levels during pregnancy

During early pregnancy, LH levels remain low—blocked by continued progesterone production. High levels of human chorionic gonadotropin (hCG) released throughout pregnancy also ensure that they stay low throughout pregnancy, so no further ovulation is triggered.

LH levels in menopause

During menopause, LH levels become elevated, although this can vary from person to person. This increase in LH levels happen as a result of the general decline in hormone production by the ovaries.

When the ovaries stop producing as much oestrogen and progesterone, the pituitary responds by increasing the production of FSH and LH, in an attempt to stimulate the ovaries. However, the ovaries become less responsive and, instead, LH levels rise.

This rise in LH levels is associated with a lot of the typical symptoms of menopause, including hot flashes and night sweats. After menopause, LH levels can decline by around 30-40%.

High LH levels

High LH levels in females outside of normal menstrual cycle fluctuations can cause fertility problems, irregular periods and early puberty.

High LH levels are often seen in people with primary ovarian insufficiency and in those with polycystic ovary syndrome (PCOS) often have elevated LH compared to their FSH. This unusual imbalance can lead to irregular periods and the overproduction of testosterone, both key symptoms of PCOS.

Sometimes LH levels can become elevated due to dietary and lifestyle factors, including:

• Smoking
• Excessive alcohol intake
• Excessive exercise
• Nutritional deficiencies 

Symptoms of high LH levels

Symptoms of high LH levels in females are more related to the underlying cause than the LH itself. However, some of the most common symptoms associated with the causes of high LH levels include:

• Difficulty getting pregnant
• A longer or shorter menstrual cycle
• Missed periods
• Weight gain or loss
• Mood swings
• Vaginal dryness
• Hot flashes
• Fatigue
• Changes in sex drive

How to lower LH levels

If your LH levels are elevated and you are a regular smoker or drinker, consider taking steps to reduce these habits.

If you’re trying to conceive, consider cutting alcohol and cigarettes completely as this will improve your chances of conception and prevent harmful effects to the baby during pregnancy.

Low LH levels

There are also a number of reasons why low LH levels might occur. Meningitis infections that have occurred in the last 12 months have been linked to low LH levels and so have eating disorders.

Sometimes, LH levels can be decreased due to dietary and lifestyle factors as well as certain medications including:

• A diet rich in soy products or isoflavones
• Excessive exercise
• Metformin
• Glucocorticoids
• Cannabis

Low LH levels in females can lead to problems with ovulation. This includes anovulation, which is not ovulating at all. This can also lead to problems with menstruation, such as irregular, missing, or complete cessation of periods.

Symptoms of low LH levels

Depending on the underlying cause, symptoms of low LH levels in females can include:

• Delayed puberty
• Irregular or no periods
• Fatigue
• Decreased pubic hair
• Problems with breast milk production

How to increase LH levels

Your diet and exercise regime can have an impact on fertility. If your LH level is on the lower side, it may be helpful to re-evaluate both of these. Excessive exercise, that is exercise without adequately fueling the body, is known to disrupt the release of GnRH from the hypothalamus which has knock-on effects on FSH and LH levels.

If you regularly consume soy or isoflavone products, these may cause excessively high levels of oestrogens. As mentioned above, this can suppress LH release from the pituitary gland.

However, data on the effects of soy on oestrogen is conflicting and further studies are needed. If you have a vegan diet and regularly use soy-based meat and dairy substitutes, you may want to consider switching to other plant-based protein sources.

If you have a prescription for glucocorticoid medication, metformin or you have had meningitis in the previous 12 months, these can temporarily decrease your LH levels by disrupting GnRH release from the hypothalamus.

Luteinising hormone blood test

The easiest way to find out your LH levels is to take an at-home test, like our Hertility Hormone & Fertility Test. From just a small blood sample, that you can do with a finger-prick test from home, the test can detect the serum LH level in your blood and provide you with the answers you’ve been searching for.

If you’ve already done a test and received an abnormal LH result, you can book an appointment with one of our Private Gynaecologists specialising in hormone and fertility concerns to discuss your results and get a personalised care plan. Appointments are available daily, with no GP referral required.

Resources

• Luteinizing hormone and its dilemma in ovulation induction. 
• The Normal Menstrual Cycle and the Control of Ovulation 
• Physiology, Luteinizing Hormone – StatPearls – NCBI Bookshelf 
• Onset of the preovulatory luteinizing hormone surge: diurnal timing and critical follicular prerequisites 
• Stimulatory and inhibitory effects of progesterone on FSH secretion by the anterior pituitary 
• Primary ovarian insufficiency: an update 
• Idiopathic primary ovarian insufficiency: a study of serial hormonal profiles to assess ovarian follicular activity
• FSH may be a useful tool to allow early diagnosis of Turner syndrome
• Follicle Stimulating Hormone (LH: FSH) Ratio in Polycystic Ovary Syndrome (PCOS) – Obese vs. Non- Obese Women 
• Relationship of GnRH‐stimulated LH release to episodic LH secretion and baseline endocrine‐metabolic measures in women with polycystic ovary syndrome 
• Ovarian function and cigarette smoking in the BioCycle Study 
• Effects of soy foods on ovarian function in premenopausal women 
• Effects of soy foods on ovarian function in premenopausal women 
• Obstetric and gynecologic problems associated with eating disorders 
• Eating disorders from a gynecologic and endocrinologic view: hormonal changes 
• A review of the pathophysiology of functional hypothalamic amenorrhoea in women subject to psychological stress, disordered eating, excessive exercise or a combination of these factors 
• Effect of Exercise on Ovulation: A Systematic Review 
• Effects of metformin administration on plasma gonadotropin levels in women with infertility, with an in vitro study of the direct effects on the pituitary gonadotrophs. – Abstract 
• Glucocorticoids, Stress, and FertilityMarihuana S