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 disorders (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 stimulates 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 inhibited by estradiol in females and testosterone in males. In males, LH triggers the release of testosterone from the testicles. In females, LH triggers 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 negative feedback 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 cause infertility and miscarriage in women and hypogonadism in men. There are currently several theories regarding the underlying cause of hypersecretion of 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 causes hypersecretion of LH. In PCOS, we see an elevation of LH and low FSH secretion. Research is mixed on the exact mechanism behind the hypersecretion of LH. It is proposed that insulin is a facilitator of LH secretion, and the link between insulin resistance and PCOS results in a direct elevation of insulin, leading to hypersecretion of LH (45).
If the underlying cause of increased LH is hyperinsulinemia, it is advised 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 implementing a Mediterranean Diet are two strategies to address 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 cause decreased LH, resulting in amenorrhea and infertility in women and hypogonadism in men.
Interestingly, chronic stress, such as strenuous exercise or extreme weight loss, can suppress the hypothalamus. Administration of exogenous glucocorticoids can also suppress 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 suppresses the secretion of FSH and LH, leading to hypogonadism, infertility, and galactorrhea (29).
Treatment of LH deficiency depends on sex, age, and underlying causes. In men, testosterone replacement therapy is a common avenue to boost hormone levels. In women who are looking to conceive, human chorionic gonadotropin (HCG) is a popular treatment option to induce ovulation.
The use of estrogen therapy in pre-pubertal girls is another potential treatment option. Women with stress–induced LH deficiency, typically see a balancing of hormones after the stressors have been removed (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 patients trying to conceive, you can use at-home urine tests to determine if you are ovulating correctly. 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 Disorders
LH plays a crucial role in both the diagnosis and management of infertility. There are several underlying causes of infertility, such as anovulation, endometriosis, diminished ovarian reserve, hormonal dysregulation, fibroids, fallopian tube blockage, and many more (49).
Regarding LH and infertility, high or low levels can cause an inability to conceive. When trying to conceive, a low LH level correlates to a lack of ovulation and warrants a more in-depth investigation of the root cause. It is known that LH stimulates the production of steroid hormones in the growing follicle during conception.
Elevated LH concentration causes a change in the hormonal environment of the follicle. Studies show that ovarian follicles exposed to prolonged elevated levels of LH result in abnormal embryo development (45).
Genetic disorders such as Klinefelter syndrome and Turner syndrome can cause disruption of LH, leading to infertility. Klinefelter syndrome is the most common cause of genetic hypogonadism in males. This disorder causes an elevation of FSH and LH, leading to androgen deficiency in adulthood.
Turner syndrome is the most common sex chromosome disorder seen in females. Individuals with Turner Syndrome have a surge in both LH and FSH at birth, suggesting the onset of ovarian failure (22, 53).
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When to Contact Your Healthcare Provider?
Consulting with a functional medicine practitioner 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, infertility, decrease in muscle mass, or development of breast tissue (gynecomastia), it is advised to seek a practitioner to diagnose and properly manage the cause of your hormonal imbalance.
In women, LH deficiency may present with hot flashes, irregular periods, loss of pubic hair, 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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