Hormones act as chemical messengers that help different parts of the body communicate. They influence growth, energy, mood, metabolism, and reproduction. When hormone levels shift, the body responds. This is why understanding key hormones can provide valuable insight into overall health.
One of the most important reproductive hormones is luteinizing hormone (LH). Many people first hear about LH when learning about fertility, ovulation tests, or hormone blood work. But LH does more than support fertility alone. It regulates menstrual cycles in females, supports testosterone production in males, and plays a role in sexual development during puberty.
Research in reproductive endocrinology shows that LH works as part of a communication system between the brain and the reproductive organs. When this system is balanced, reproductive processes function normally. When LH levels become too high or too low, it may signal a hormonal imbalance or reproductive health concern.
Because LH levels rise and fall at specific times, measuring LH can provide useful information about fertility, menstrual cycle health, and hormone regulation. This is why LH testing is commonly included in fertility evaluations and hormone assessments.
In this guide, you will learn what luteinizing hormone is, where it is produced, how it functions in females and males, what normal LH levels look like, and what high or low LH levels may mean.
What is Luteinizing Hormone
Luteinizing hormone is a reproductive hormone produced by the pituitary gland, a small gland located at the base of the brain. The pituitary gland receives signals from another brain region called the hypothalamus. In response, it releases LH into the bloodstream.
Once LH enters circulation, it travels to the ovaries in females and the testes in males. There, it sends signals that activate essential reproductive processes.
LH belongs to a group of hormones called gonadotropins. Another key gonadotropin is follicle stimulating hormone, or FSH. Research shows that LH and FSH work together to regulate reproductive function. FSH supports early stages of egg and sperm development, while LH triggers later stages such as ovulation and testosterone production.
Function Overview of Luteinizing Hormone
Luteinizing hormone acts as an activation signal for the reproductive system.
In females, LH regulates the menstrual cycle and triggers ovulation. Studies on cycle regulation show that a sudden rise in LH, called the LH surge, is the key event that causes the ovary to release a mature egg. Without this surge, ovulation does not occur.
After ovulation, LH supports progesterone production. Progesterone prepares the uterus for a possible pregnancy. If pregnancy does not occur, hormone levels drop and the next cycle begins.
In males, LH stimulates the testes to produce testosterone. Research in male reproductive health shows that stable LH signaling is necessary to maintain normal testosterone levels. Testosterone supports sperm production, muscle mass, bone strength, energy levels, and sex drive.
Because LH directly influences ovulation and testosterone production, it plays a central role in fertility and reproductive health in both sexes.
Role of Luteinizing Hormone in Females
In females, LH is essential for maintaining a healthy menstrual cycle.
During the first part of the cycle, LH works alongside FSH to support ovarian follicle growth. Each follicle contains an egg preparing for release. Steady LH signaling during this phase helps the ovary prepare a mature egg for ovulation.
Which hormone triggers ovulation
LH is the hormone responsible for triggering ovulation.
As estrogen levels rise, the brain releases a surge of LH. This LH surge signals the ovary to release a mature egg, usually around the middle of the cycle.
After ovulation, LH stimulates progesterone production. Progesterone prepares the uterine lining for a possible pregnancy. If pregnancy does not occur, hormone levels fall and menstruation begins.
LH changes across life stages
LH levels remain low during childhood, rise during puberty, fluctuate throughout the reproductive years, and increase again during perimenopause and menopause.
Higher LH levels during menopause occur because estrogen and progesterone decline, and the brain increases LH release in response. Understanding these natural patterns helps explain why LH testing is often used in fertility evaluation and menopause assessment.
Role of Luteinizing Hormone in Males
In males, LH supports continuous testosterone production.
Consistent LH signaling is needed to maintain normal testosterone levels, which support sperm production, energy, muscle strength, and sexual health.
Testosterone is essential for:
- Sperm production
- Muscle development
- Bone health
- Energy levels
- Sex drive
Unlike females, males do not experience monthly LH surges. Instead, LH is released in steady pulses throughout the day to maintain hormonal stability.
When LH levels are abnormal, testosterone production may be affected. This is why LH testing is often included in evaluations for fertility concerns or low testosterone symptoms.
Role of LH in puberty
During childhood, LH levels remain very low. As puberty begins, the brain increases signals to the pituitary gland, which raises LH production.
In females, rising LH stimulates estrogen production and the start of menstrual cycles.
In males, rising LH increases testosterone production and sexual development.
Research shows that abnormal LH levels during childhood can lead to early or delayed puberty. This is why LH testing is sometimes used when puberty timing is a concern.
Normal luteinizing hormone levels
LH levels vary based on sex, age, and in females, the phase of the menstrual cycle. LH follows predictable patterns throughout life and across the menstrual cycle.
LH levels in females
- Low during early menstrual cycle
- Highest during the LH surge at ovulation
- Lower after ovulation
- Higher after menopause
Because of these natural changes, healthcare providers always interpret LH test results based on cycle timing.
LH levels in males
In males, LH levels remain relatively steady after puberty to support continuous testosterone production.
Why normal ranges vary
Normal LH ranges may differ slightly between laboratories. This is why test results should always be reviewed with a healthcare provider rather than interpreted on their own.
What high luteinizing hormone levels may mean
High LH levels usually mean the brain is sending strong signals, but the ovaries or testes are not responding as expected.
In females
High LH may be associated with:
- Polycystic ovary syndrome
- Perimenopause or menopause
- Ovarian function changes
In these situations, the pituitary gland increases LH release to stimulate the ovaries.
If high LH levels are linked to perimenopause or menopause, hormone therapy may sometimes be considered to help manage symptoms under the guidance of a healthcare provider.
In males
In males, high LH may indicate reduced testosterone production despite strong brain signaling.
High LH alone does not confirm a diagnosis, but it provides useful information for further evaluation.
What low luteinizing hormone levels may mean
Low LH means the pituitary gland is not releasing enough hormone to stimulate the reproductive organs.
Possible causes
Low LH may result from:
- Pituitary or hypothalamus disorders
- Chronic stress
- Significant weight loss
- Long term illness
Effects in females
Low LH can prevent normal ovulation, leading to irregular or absent periods.
Effects in males
Low LH can reduce testosterone production, which may cause fatigue, reduced muscle mass, low sex drive, and fertility concerns.
Low LH typically requires further hormone testing to identify the underlying cause.
LH and ovulation testing
Ovulation predictor kits detect the LH surge in urine. A positive test means ovulation is likely within the next 24 to 36 hours.
Tracking LH over several cycles can also help identify irregular ovulation patterns. However, LH testing alone does not confirm overall reproductive health. Doctors often combine LH results with other hormone tests for accurate assessment.
When LH testing may be recommended
Healthcare providers may suggest LH testing when there are:
- Irregular menstrual cycles
- Difficulty conceiving
- Symptoms of perimenopause or menopause
- Low testosterone symptoms in males
- Concerns about early or delayed puberty
LH testing is usually part of a broader hormone evaluation.
Common questions about luteinizing hormone
- Which hormone triggers ovulation
Luteinizing hormone triggers ovulation through the LH surge. - What hormone is high during ovulation
LH is the hormone that rises sharply during ovulation. - Can pregnancy occur if LH is low
Pregnancy may still be possible, but low LH can interfere with normal ovulation. Medical evaluation helps determine the cause. - Is LH used to confirm pregnancy
No. Pregnancy is confirmed using hCG hormone, not LH.
Bottom line
Luteinizing hormone (LH) is a key reproductive hormone that helps regulate ovulation in females and testosterone production in males. Because LH levels naturally change across different life stages, testing LH can offer useful insight into overall hormone balance.
If you experience irregular periods, fertility concerns, symptoms of low testosterone, or signs of menopause transition, a hormone evaluation that includes LH testing can help identify possible imbalances. If LH levels fall outside the expected range, consulting a healthcare provider for further assessment is the best next step. With proper evaluation and guidance, most hormone-related concerns can be effectively managed.
