LH: the luteinising hormone in charge of the reproductive cycle

Due to its importance in fertility, the LH hormone is also very important in assisted reproduction treatments, generally combined with drugs containing FSH, with the aim of optimising the ovarian response and improving the chances of success in the search for pregnancy.

We talked to the medical director of Vida Fertility Alicante, Dr. Alejandra García-Villalba about the LH hormone, its functions, normal values and what happens if it is altered during a fertility treatment.

Dra alejandra García-Villalba vida fertility

What is LH hormone and what is its function?

Luteinizing hormone (LH) is a gonadotropin produced in the pituitary gland, located in the brain, and plays an essential role in the reproductive system of both men and women.

Together with follicle stimulating hormone (FSH), LH helps to regulate hormonal balance and reproductive function from puberty onwards:

In males, its main function is to stimulate the production of testosterone in the testes, a process known as steroidogenesis.
In females, LH promotes the production of androgens in the ovaries, which are subsequently transformed into oestrogen. In addition, this hormone is responsible for inducing ovulation in the middle of the menstrual cycle.

Normal values in women

To assess hormonal balance and ovarian function, it is recommended to perform a luteinising hormone (LH) test at the beginning of the menstrual cycle. At this stage, LH levels are in their basal state and can be compared with established reference values.

Measurement of LH is usually requested together with other key fertility hormones such as FSH, oestradiol, TSH and prolactin to obtain a more complete assessment of the reproductive system.

Normal LH values: On day 3 of the menstrual cycle, LH levels usually range between 2 and 10 mIU/ml.

When results show values outside this range, possible causes may include:

Low LH: May be related to conditions such as hypogonadism, alterations in hypothalamic function, eating disorders, hyperprolactinaemia, pituitary dysfunction or Kallman’s syndrome.
High LH: May indicate early menopause, Turner syndrome, congenital adrenal hyperplasia, polycystic ovarian syndrome (PCOS) or pituitary tumours.

Impact on female fertility: Abnormal LH levels can cause menstrual irregularities and even amenorrhoea (absence of menstrual periods), directly affecting ovulation and the ability to conceive.

Normal values in men

LH analysis in men is a key test to evaluate testicular function and detect possible alterations in the production of male sex hormones. This assessment can diagnose problems of testicular failure or possible abnormalities in the hypothalamic-pituitary axis.

Normal LH values in men: In adults, LH levels are usually between 1 and 9 mIU/ml.

When results are outside this range, they may be associated with various medical conditions:

Low LH: May be related to hypogonadism, hypothalamic dysfunction, eating disorders, hypopituitarism or Kallman’s syndrome.
High LH: May be indicative of testicular failure, Klinefelter’s syndrome, anorchia (absence of testes), pituitary tumours.

Importance in male fertility: Men with semen quality problems or difficulty conceiving often undergo this test to identify hormonal imbalances that may be affecting their fertility.

Use of LH in Assisted Reproduction

The use of luteinising hormone (LH) in fertility treatments is indicated for certain profiles of women who may benefit from its administration to improve the results of ovarian stimulation.

The main cases in which its use is recommended include the following:

Women with low ovarian response: Those who, in previous cycles, have obtained few oocytes with FSH stimulation alone. In these cases, incorporating LH into the protocol can optimise ovarian response.
Women with hypogonadotropic hypogonadism: Patients with absence of menstruation (amenorrhoea) or irregular and widely spaced menstrual cycles (oligomenorrhoea).
Women with reduced basal levels of gonadotropins: low levels of LH and/or FSH can affect ovarian maturation, so supplementation may be necessary.

What are the benefits in fertility treatments?

The administration during controlled ovarian stimulation in Artificial Insemination (AI) or In Vitro Fertilisation (IVF) can provide multiple advantages:

More physiological hormone levels: stimulation more closely resembles the body’s natural processes.
It can improve oestradiol production: levels of this hormone, which is essential for ovarian maturation and endometrial development, are optimised.
Optimal preparation of the endometrium: by favouring the production of oestradiol by the follicles.

According to Dr. Alejandra García-Villalba, ‘To take advantage of these benefits, it is essential for the medical team to design an individualised administration schedule, adapted to the needs of each patient. An appropriate adjustment of LH in ovarian stimulation can make the difference in the success of the treatment’.

Frequently asked questions about LH hormone

What is a normal level?

Luteinising hormone (LH) levels in the body are usually in the range of 2 to 10 mIU/ml under normal conditions. However, when this hormone exceeds 15-20 mIU/ml in the follicular phase, it indicates that ovulation is close to occurring.

In conjunction with progesterone, LH is a key marker for assessing whether ovulation is proceeding properly. However, it is important to note that elevated LH values at the beginning of the menstrual cycle may be related to certain hormonal disorders, such as polycystic ovarian syndrome (PCOS) or even be an indicator of perimenopause or menopause.

What happens if my LH is low?

Low levels of luteinising hormone (LH) can be associated with a number of medical conditions in both men and women. Some of the main causes include:

Hypogonadotropic hypogonadism: a dysfunction in sex hormone production due to insufficient stimulation from the pituitary gland.
Hyperprolactinaemia: elevated prolactin levels can inhibit the release of LH, affecting ovulation in women and testosterone production in men.
Hypopituitarism: a failure of the pituitary gland that decreases the production of several hormones, including LH.
Eating disorders: anorexia or severe nutritional deficit can disrupt the hormonal axis and reduce gonadotropin secretion.
Kallman’s syndrome: a rare genetic condition that causes failure of gonadotropin production, affecting fertility.

Since LH is key in the regulation of the ovarian cycle in women and testosterone production in men, its deficiency can lead to fertility problems, ovulatory dysfunction and reduced sperm quality.

Difference between LH and FSH hormone

The hormones responsible for regulating the menstrual cycle and, consequently, the growth and maturation of ovarian follicles are LH (luteinising hormone) and FSH (follicle stimulating hormone).

These hormones are produced by the pituitary gland in response to gonadotropin-releasing hormone (GnRH) stimulation.

FSH plays a key role in stimulating follicular development, promoting oocyte maturation.
LH is responsible for inducing the ovulation process, allowing the release of the mature egg.

Which hormone indicates infertility??

Although there are certain hormones that can indicate fertility problems, anti-Müllerian hormone (AMH) is a key indicator of a woman’s ovarian reserve.

When AMH levels are adequate depending on age, it means that ovarian reserve is normal. However, over the years, these values tend to progressively decrease, which impacts on female fertility.

However, in men, anti-Müllerian hormone (AMH) is not as accurate an indicator as it is in women. In general terms, the analysis of FSH and LH, together with inhibin, provides a more reliable assessment of testicular function and sperm production.

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