What Is Luteinizing Hormone?
Luteinizing hormone (LH) is secreted along with follicle-stimulating hormone (FSH) by gonadotropin cells in the pituitary. LH plays a critical role in the development of the reproductive system in males and females.
LH works in tandem with other sex hormones to regulate the menstrual cycle and fertility. In this article, we will discuss the functions of LH and its impact on reproductive health (36).
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What Is the Luteinizing Hormone’s Function?
Luteinizing hormone (LH) plays an essential role in the reproductive system of men and women. LH is involved in the production of testosterone in men and estradiol in women. LH is also a crucial hormone in children and infants. Before puberty, there is a gradual increase in LH at nighttime. Once puberty starts, LH increases slowly, which supports gonadal maturation (36).
Where Is the LH Located?
Luteinizing hormone (LH) is part of a hormonal cascade that starts in the brain. The hypothalamus releases gonadotropin-releasing hormone (GnRH), which triggers the anterior pituitary to release LH and follicle-stimulating hormone (FSH). LH is influenced by estradiol in females and testosterone in males. In males, LH supports the release of testosterone from the testicles. In females, LH supports the release of sex steroids and estrogen from the ovaries (28).
LH is also a crucial hormone in regulating ovulation and assists in the implantation of an egg. When LH is released from the anterior pituitary, it directly impacts ovarian follicles.
LH causes an increase in estradiol production, which leads to a feedback mechanism on the anterior pituitary, causing an LH surge. The sudden rise in LH signals ovulation to begin. Once ovulation has begun, the ruptured follicle transforms into the corpus luteum.
The corpus luteum is responsible for the production of progesterone, which plays an essential role in preparing the uterine lining for the implantation of a fertilized egg. LH also helps regulate the length of the menstrual cycle and progesterone production after ovulation (36).
Conditions and Disorders Associated with Luteinizing Hormone Issues
Certain conditions may be linked to either high or low levels of LH:
High LH Levels
Elevated levels of LH may be associated with challenges in fertility and reproductive health in women and may affect hormone balance in men. There are currently several theories regarding the underlying cause of increased LH from the pituitary. Some proposed mechanisms include hypothalamic dysfunction causing increased GnRH release, a change in pituitary sensitivity to GnRH, and hyperinsulinemia stimulation of the anterior pituitary (4).
Polycystic Ovarian Syndrome (PCOS) is a common condition that may be linked to increased LH levels. In PCOS, we see an elevation of LH and low FSH secretion. Research is mixed on the exact mechanism behind the increased LH. It is proposed that insulin may play a role in LH secretion, and the link between insulin resistance and PCOS results in a direct elevation of insulin, potentially leading to increased LH (45).
If the underlying cause of increased LH is hyperinsulinemia, it may be helpful to address insulin resistance through diet, lifestyle, and if needed, supplementation. Risk factors for insulin resistance include physical inactivity and nutritional imbalance. Decreasing sugar intake and considering a Mediterranean Diet are two strategies to explore for managing insulin resistance (55).
Low LH Levels
Luteinizing hormone deficiency can be genetic or acquired during life. The causes of LH deficiency range from disorders involving the hypothalamus, pituitary, or ovaries. Hypothalamic causes include Kallmann syndrome, which is a congenital cause of low LH. Although rare, it is possible to have genetic mutations of the LH receptors, which may affect LH levels, potentially impacting reproductive health in women and men.
Interestingly, chronic stress, such as strenuous exercise or extreme weight loss, can influence the hypothalamus. Administration of exogenous glucocorticoids can also affect luteinizing hormone (23).
Pituitary causes of low LH include prolactinoma or Sheehan Syndrome. A prolactinoma is a tumor in the pituitary that secretes prolactin, which may influence the secretion of FSH and LH, potentially affecting reproductive health (29).
Approaches to managing LH deficiency depend on sex, age, and underlying causes. In men, testosterone replacement therapy is a common avenue to support hormone levels. In women who are looking to conceive, human chorionic gonadotropin (HCG) is a popular option to support ovulation.
The use of estrogen therapy in pre-pubertal girls is another potential option. Women with stress–induced LH deficiency may see a balancing of hormones after the stressors have been managed (29).
Testing for LH Levels
You can measure LH through blood, urine, and salivary tests. When completing any method of LH testing, it is crucial to measure at the correct time during the menstrual cycle. For menstruating women, ovulation typically occurs anywhere from days 13 to 15, which should be the window in which you test for LH.
For individuals trying to conceive, you can use at-home urine tests to determine if you are ovulating. This is an easy, affordable method to assist in fertility planning. For a more comprehensive urinary hormone test, the DUTCH Cycle Mapping test will examine all hormones and hormone metabolites (17).
LH measurements can also be assessed through saliva (less common) and blood. Blood testing of hormones is standard in clinical practice due to its convenience. However, blood testing only captures a single snapshot of hormone levels and may miss fluctuations in hormone levels over time. Saliva testing of hormones, such as the Rhythm Plus™ by Genova Diagnostics is useful because it measures the biologically active form of the hormone (21).
LH and Reproductive Health
LH plays a crucial role in both the understanding and management of infertility. There are several underlying factors that may contribute to infertility, such as anovulation, endometriosis, diminished ovarian reserve, hormonal dysregulation, fibroids, fallopian tube blockage, and many more (49).
Regarding LH and fertility, high or low levels can influence the ability to conceive. When trying to conceive, a low LH level may correlate to a lack of ovulation and warrants a more in-depth investigation of the root cause. It is known that LH supports the production of steroid hormones in the growing follicle during conception.
Elevated LH concentration may cause a change in the hormonal environment of the follicle. Studies show that ovarian follicles exposed to prolonged elevated levels of LH may result in changes in embryo development (45).
Genetic factors such as Klinefelter syndrome and Turner syndrome can influence LH, potentially affecting fertility. Klinefelter syndrome is a common genetic factor associated with hormone balance in males. This condition may lead to changes in FSH and LH, affecting hormone levels in adulthood.
Turner syndrome is a common sex chromosome condition seen in females. Individuals with Turner Syndrome may experience changes in both LH and FSH at birth, suggesting the onset of ovarian changes (22, 53).
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When to Contact Your Healthcare Provider?
Consulting with a healthcare provider is important if you are experiencing hormonal imbalance. In men, if you are experiencing signs and symptoms of hypogonadism, such as decreased sex drive, fatigue, depression, erectile dysfunction, changes in fertility, decrease in muscle mass, or development of breast tissue (gynecomastia), it is advised to seek a practitioner to explore and manage the cause of your hormonal imbalance.
In women, LH deficiency may present with hot flashes, irregular periods, changes in hair growth, mood changes, and fatigue. If you are experiencing any of these symptoms, consult with a healthcare provider to run the necessary tests. Regulating hormones is a complex process and should always be done under the care of a supervised physician (32, 33).
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