What are the functions of the LH hormone in the reproductive cycle?

Luteinizing hormone (LH) is a type of gonadotropin that is synthesized in the pituitary gland of the brain in both males and females.

Together with follicle stimulating hormone (FSH), LH has the function of regulating the reproductive and endocrine system in both sexes once puberty is reached:

In men

stimulates the production of steroid hormones in the testicle, such as testosterone (steroidogenesis).

In women

stimulates the production of androgens in the ovaries, which are the precursors of estrogens (female hormones). It is also the hormone responsible for triggering ovulation in the middle of the menstrual cycle.

In addition, LH is used in assisted reproduction treatments in combination with drugs that also contain FSH

The different sections of this article have been assembled into the following table of contents.

What is the function of LH in women?

The LH hormone begins to be synthesized in the pituitary once the female has reached sexual maturity with the arrival of the first menstruation. Its production is regulated by gonadotropin-releasing hormone (GnRH) in response to other stimuli.

At the beginning of the female menstrual cycle, the LH hormone is at basal levels. As estrogen levels increase due to the development of ovarian follicles, LH receptors begin to be expressed in their cells.

Finally, when a preovulatory follicle or de Graaf's follicle has developed and is ready to mature and estrogens are very high, continuous LH release is triggered for a period of 24 to 48 hours. This LH surge is known as lH spike and is what triggers ovulation.

Role of LH in the menstrual cycle

The LH surge also induces the conversion of the preovulatory follicle into a corpus luteum, which will be responsible for producing the hormone progesterone to mature the endometrium and allow embryo implantation.

Another important function of LH is to stimulate the theca cells in the ovary to produce androgens, the hormonal precursors of female sex hormones such as estradiol.

Normal values

LH should be tested at the beginning of the menstrual cycle, when its level is at baseline and can be compared to a reference value.

Normally, the determination of LH is requested in conjunction with other hormones such as FSH, estradiol, TSH, prolactin, etc.

In case of obtaining an abnormal LH value, the causes could be the following:

Low LH

hypogonadism, hypothalamic suppression, eating disorder, hyperprolactinemia, hypopituitarism or Kallman syndrome.

High LH

early menopause, Turner syndrome, Swyer syndrome, congenital adrenal hyperplasia, polycystic ovarian syndrome or pituitary tumor.

Altered LH values in women

All these alterations can cause alterations in menstruation and amenorrhea, i.e., the absence of menstruation.

LH in men

As in females, LH synthesis in males begins with the onset of puberty. LH is responsible for the production of male sex hormones, androgens, which cause the appearance of secondary sexual characteristics.

Steroidogenesis takes place in the Leydig cells of the testis. Thanks to the action of LH, these cells synthesize testosterone, the hormone responsible for stimulating the formation of spermatozoa (spermatogenesis) in the seminiferous tubules.

Role of LH in spermatogenesis

Testosterone also has a regulatory role in the male reproductive cycle. When its levels are very high, testosterone sends a signal to the brain, which stops releasing GnRH and, therefore, there is also no LH secretion. This is what is known as a negative feedback system.

Normal values

The analysis of LH in the male serves to diagnose a problem of testicular insufficiency or brain abnormality.

In case of obtaining an abnormal LH value, the causes could be the following:

Low LH

hypogonadism, hypothalamic suppression, eating disorder, hypopituitarism or Kallman syndrome.

High LH

castration, testicular failure, Klinefelter's syndrome, anorchia or pituitary tumor.

Altered LH values in men

Males with poor seminal quality or other types of infertility also often have this hormonal test.

LH drugs

Drugs composed of the LH hormone are prescribed in women during the controlled ovarian stimulation phase of artificial insemination (AI) or in vitro fertilization (IVF).

This is done to reproduce as closely as possible the conditions that occur in the follicular phase of a woman's natural menstrual cycle.

Normally, the administration of LH is done in conjunction with a drug that also contains FSH, the other pituitary hormone that regulates the menstrual cycle.

What types of LH drugs are there?

There are two types of LH drugs depending on how the hormone is obtained:

Urinary LH

obtained by purification from the urine of postmenopausal women. This is known as hMG (human menopausal gonadotropin) which contains 75 IU of FSH and 75 IU of LH. The drugs containing it are Menopur and HMG lepori.

Recombinant LH

obtained by genetic engineering. One of the drugs containing recombinant LH alone is Luveris. There is also another drug, Pergoveris, which contains 75 IU of recombinant LH and 150 IU of recombinant FSH.

Hormonal drugs with LH

If you want to learn more about each of these drugs, you can continue reading here: Medications used in controlled ovarian stimulation.

Indications

The use of LH in assisted reproduction is aimed at three main types of women:

• Low responders, who in previous cycles have not obtained many eggs with FSH stimulation alone. It is possible that better results may be obtained by adding LH to the protocol.
• Women with hypogonadotropic hypogonadism who present amenorrhea or very few menses (oligomenorrhea).
• Women with very low baseline levels of LH and/or FSH gonadotropins.

When are LH drugs indicated?

For more information about other gonadotropins and their indications, please visit this link: Gonadotropins: What are they and what are their functions?

What are the advantages of using LH drugs?

The advantages of administering LH during controlled ovarian stimulation in AI or IVF are as follows:

• LH levels are more similar to physiological levels
• It is possible to obtain a higher number of eggs in the stimulation
• Improved serum estradiol level
• The endometrium is better prepared to receive embryos at transfer
• Improved implantation and pregnancy rates

Benefits provided by LH drugs

In order for patients to benefit from all these advantages, it is necessary for the physician responsible for the treatment to indicate a personalized drug regimen, so that the ideal amount of LH is received.

Disadvantages

The main disadvantage of LH administration is that this hormone acts in a dependent manner, i.e., depending on its concentration, it produces one effect or the opposite.

On the one hand, too high LH levels can inhibit estrogen synthesis and affect egg maturation, causing follicles to become atretic or undergo premature luteinization.

On the other hand, too low LH levels can produce poor simulation results, such as a low response.

FAQs from users

What hormones are analyzed to determine the cause of male infertility?

Among the multiple causes of male sterility are those that depend on the interaction between the brain and the testicle, and it is in these cases where it is of interest to request a hormonal study, through the FSH (follicle stimulating hormone) and LH (luteinizing hormone). Their determination will indicate the state of the pituitary-testicular axis.

What is the LH test?

The LH test or ovulation test is a test similar to the pregnancy test, but measures the level of the hormone LH in urine in order to detect a woman's fertile days, when the LH peak that triggers ovulation occurs.

Is it common to use LH drugs for ovarian stimulation in assisted reproduction?

Gonadotropins are hormones capable of binding to their receptors in the ovary and stimulating follicular recruitment, development and maturation, a process necessary for the antral follicles to become preovulatory follicles containing mature oocytes capable of being fertilized.

The main gonadotropins involved in this process are Follicle Stimulating Hormone (FSH) and Luteninizing Hormone (LH), with FSH playing the most important and indispensable role in the follicular development stage. And, LH is the hormone that would be more involved in the process of final follicular maturation and follicular rupture, what we know as "ovulation". Even so, the synergistic action of LH together with FSH during the follicular development process can also be important during follicular development in some specific cases.

What does it mean to have a low luteinizing hormone?

There are several reasons that can cause LH depletion in both men and women. Among them: hypogonadism, hyperprolactinemia, hypopituitarism, eating disorders, Kallman's syndrome, etc.

What is the significance of having a high LH?

Most likely when an elevated LH is obtained in female fertility tests, these women have early menopause or polycystic ovarian syndrome (PCOS).

It should be noted that women with PCOS have an LH value that is almost twice that of FSH.

Recommended readings

If you need more information about the functioning of all the sex hormones that exist in addition to LH, you can access the following post: Male and female sex hormones.

As mentioned above, LH drugs are administered during the ovarian stimulation phase of assisted reproduction treatments. To know in more detail what this phase consists of, you can read the following article: What is ovarian stimulation?

References