Receiving a blood test result showing a value for luteinizing hormone (LH) can raise questions. Understanding this marker is an essential step to better grasp your health status. It’s not a mysterious code, but precious information about the functioning of your hormonal system. This article aims to provide you with clear and factual explanations. This way, you can better communicate with your doctor and actively participate in managing your health.

What is Luteinizing Hormone (LH)?

Luteinizing hormone, or LH, is a crucial chemical substance produced by the pituitary gland. This small gland, located at the base of the brain, manufactures it under the direction of the hypothalamus. The hypothalamus releases another hormone, GnRH, to trigger LH production. This mechanism illustrates complex communication within the brain.

In the body, LH acts as an orchestrator for reproduction. In women, its best-known action is to trigger ovulation. An LH surge signals to the ovary that it’s time to release a mature egg. Then, LH helps in the formation of the corpus luteum. This temporary structure secretes progesterone, a hormone that prepares the uterus for a potential pregnancy.

In men, luteinizing hormone (LH) has an equally crucial function. It stimulates specific cells in the testes, the Leydig cells, to produce testosterone. Testosterone is essential for the development of masculine characteristics and the production of sperm.

Why is Luteinizing Hormone (LH) Testing Important?

Luteinizing hormone (LH) testing provides a clear view of the reproductive axis function. Since its discovery in the 1920s, the understanding of its role has evolved considerably. Scientific advancements have led to concrete medical applications, particularly in the field of assisted reproductive technology.

An abnormal variation in LH levels can be a sign of an underlying condition. For example, high LH levels in women are often observed in polycystic ovary syndrome (PCOS). This condition, which affects about 6 to 13% of women of reproductive age according to the WHO, can impact fertility and increase long-term metabolic risks.

In men, high LH combined with low testosterone can reveal dysfunction of the testes, or primary hypogonadism. This condition can lead to decreased muscle mass, increased fat mass, and reduced libido.

Therefore, measuring LH is a tool that guides important medical decisions. In fertility journeys, monitoring the LH surge allows for precise scheduling of certain medical procedures. For women with irregular cycles, it helps determine if ovulation is occurring.

How to Interpret a Luteinizing Hormone (LH) Test?

Your result sheet will show the abbreviation “LH” followed by a value and a unit, often “mIU/mL” (milli-International Units per milliliter). Next to it, reference values are indicated.

It’s essential to note that these norms vary. Each laboratory may have its own reference ranges. Furthermore, normal values depend on sex, age, and, for women, the phase of the menstrual cycle.

Here are generally accepted ranges:

• Women of reproductive age:
  • Follicular phase: 2-15 mIU/mL
  • Ovulatory peak: 20-100 mIU/mL
  • Luteal phase: 2-15 mIU/mL
• Postmenopausal women: 15-62 mIU/mL
• Adult men: 2-12 mIU/mL
• Prepubertal children: < 1 mIU/mL

To read your results, identify your value and compare it to the norm corresponding to your personal situation. A doctor will always interpret this figure by correlating it with other hormones (FSH, estradiol, progesterone, testosterone) and your clinical context.

What Conditions Are Linked to Abnormal LH Levels?

A luteinizing hormone (LH) value outside the norm can indicate different clinical situations.

Conditions Associated with High LH Levels

• Polycystic Ovary Syndrome (PCOS): In women, this is a very common cause of a high LH/FSH ratio. This hormonal imbalance disrupts the development of ovarian follicles and ovulation. Symptoms may include irregular cycles, excessive hair growth, or acne.
• Premature Ovarian Failure: This condition, which affects about 1% of women before age 40, corresponds to the exhaustion of ovarian reserve. The pituitary gland then produces a lot of LH and FSH in an attempt to stimulate ovaries that no longer respond.
• Primary Hypogonadism in Men: This is a defect in testosterone production by the testes, despite strong stimulation by LH. Causes can be genetic (Klinefelter syndrome) or acquired (trauma, infection).

Conditions Associated with Low LH Levels

• Hypogonadotropic Hypogonadism: This rarer disorder stems from a defect in LH and FSH production by the pituitary gland or hypothalamus. It can be congenital (Kallmann syndrome) or acquired (tumor, trauma). It manifests as delayed puberty or cessation of sexual development.
• Hyperprolactinemia: An excess of another hormone, prolactin, can inhibit LH production. This situation can be due to a small benign pituitary tumor or certain medications.
• Anorexia Nervosa: Severe malnutrition puts the hormonal system on standby. The body then reduces the production of reproductive hormones, including LH, leading to cessation of menstrual cycles.

Practical Advice and Monitoring LH Levels

When faced with a variation in luteinizing hormone (LH) levels, lifestyle adjustments can be beneficial. However, they never replace medical advice.

Nutrition and Lifestyle

A balanced diet and a healthy lifestyle support overall hormonal balance.

• Favor a healthy diet: Foods with a low glycemic index, rich in omega-3s (fatty fish, nuts), zinc (seafood, seeds), and B vitamins can be helpful.
• Maintain a healthy weight: Both overweight and underweight can disrupt the hormonal axis and LH levels.
• Manage stress: Chronic stress can interfere with hormones. Practices like meditation or yoga can help regulate it.
• Engage in moderate physical activity: Too intense activity can lower LH, while regular and moderate activity is beneficial.

When to Consult a Specialist?

It’s important to consult a doctor, gynecologist, or endocrinologist in the following situations:

• For a woman, consistently high LH levels outside the ovulation peak.
• For a man, high LH levels associated with fatigue or decreased libido.
• For an adolescent, delayed puberty with very low LH.
• Any sudden, unexplained variation in LH.

Only a healthcare professional can make a precise diagnosis and propose appropriate management.

Frequently Asked Questions about Luteinizing Hormone (LH)

What is the difference between the follicular phase and the luteal phase for LH?

The follicular phase is the first part of the menstrual cycle. During this phase, LH is relatively low and then gradually increases to reach a peak that triggers ovulation. Conversely, the luteal phase, after ovulation, is characterized by a drop in LH levels, which remain low. This dynamic is essential for the proper progression of the cycle.

Can one have cycle disorders with normal LH?

Yes. Luteinizing hormone (LH) is just one element of the reproductive system. Irregular cycles can occur even with normal LH levels if other hormones are unbalanced, or in case of issues with the uterus or ovaries. This is why a complete evaluation is often necessary.

Which medications can influence LH levels?

Several medications can alter test results. Hormonal contraceptives suppress LH production. Certain antiepileptics, hormone treatments (like aromatase inhibitors), or long-term opioid use can also affect LH levels. It is therefore crucial to inform your doctor about all your medications.

What is the exact relationship between the LH surge and ovulation?

The LH surge is the direct trigger for ovulation. Ovulation, which is the release of the egg from the ovary, occurs approximately 24 to 36 hours after the start of this sharp rise in LH. Urinary ovulation tests detect this surge to help identify the most fertile period of the cycle.

How does 17-OH progesterone interact with luteinizing hormone?

17-OH progesterone is a precursor to other hormones. LH indirectly influences its levels through its action on the corpus luteum after ovulation. The combined analysis of LH and 17-OH progesterone can help diagnose complex endocrine disorders, such as certain forms of PCOS or congenital adrenal hyperplasia.

Conclusion

Luteinizing hormone (LH) is a key indicator of reproductive and hormonal health. Understanding its role and knowing how to interpret your results allows you to be an informed participant in your health journey. This marker helps detect certain imbalances early and guide medical decisions. Never forget that the final interpretation of your results should always be done by a healthcare professional, who will put them into perspective with your overall situation.

Additional resources

• To deepen your knowledge of this blood marker, click here.
• To extend your knowledge and decipher other markers, more articles are available here.

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