Hormones & Cycles

Your Luteinizing Hormone: Function, Symptoms and more

Did you know? The luteinizing hormone (also called lutropin) is found in both women and men and it is involved in controlling your reproductive system.

What’s the function of the Luteinizing Hormone?

The luteinising hormone (LH) is produced in the pituitary gland (hypophysis) and gets released into the blood when it’s needed by your body. In women, the luteinising hormone (LH) (like the follicle stimulating hormone (FSH)), is responsible for the production of estrogen in the ovaries and the maturation of eggs. It’s also responsible for ovulation, which is why a high concentration of luteinising hormone is found in the blood shortly before ovulation. After ovulation, the concentration of LH in the blood decreases again. If your body produces too little luteinising hormone, it can be one of the reasons for difficulties in getting pregnant. This is why it is also used in fertility treatments such as IVF (in vitro fertilization). To ensure that several eggs mature simultaneously in the woman's body, both the luteinising hormone and the follicle-stimulating hormone are injected during preparation for IVF.

How does our body know how much LH is needed?

When and how much LH is needed is regulated by your Gonadotropin-releasing hormone (GnRH, or LH-releasing hormone). The Luteinizing hormone is released in a part of your brain, the anterior pituitary gland, and is converted into testosterone and estrogen as described. If the GnRH recognizes that these hormones are present in sufficient quantities, it stops the release. (1,2) This very sensitive regulation is linked to your monthly cycle and in close coordination with other hormones, a high concentration of the luteinizing hormone triggers ovulation. After ovulation, the remaining follicle transforms into the corpus luteum again under the influence of LH (hence the name luteinising = yellow). This produces the hormones progesterone and estrogen. In addition to the formation of testosterone, LH also causes the maturing process of the sperm and is therefore an essential factor on the male side in a couple trying to conceive.

The cycle of your Luteinizing Hormone

During menstruation, the concentration of the Luteinising hormone is low, but with the end of your period phase, the concentration of LH in your blood slowly begins to rise again. This increase ensures that [estrogen]/blog/entry/all-you-need-to-know-about-estrogen) and progesterone are produced in the body. In the first two weeks of the cycle, estrogen causes the lining of the uterus (also called endometrium) to grow and a follicle containing the egg grows in the ovary. When estrogen reaches its peak, it signals the pituitary gland to produce LH and FSH and the increase in these two hormones then initiates ovulation. When ovulation occurs, the egg is released from the follicle, which is located in the ovary, into the fallopian tube. After ovulation, the luteinising hormone ensures that a corpus luteum is formed from the empty follicle and the concentration of LH and FSH decreases again. During this time the concentration of progesterone increases. Progesterone is a hormone that ensures that the uterine lining is better supplied with blood and thus becomes softer and like a sponge. This way the uterine lining is optimally prepared to implant the fertilized egg. You can read more about Progesterone here. If the egg is not fertilized, the amount of progesterone in the blood drops again. As a result, the uterine lining is again less supplied with blood and the outer layer of the uterine lining detaches and is washed out of the body with menstruation.

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Why is the concentration of LH measured?

For women, the determination of LH is mainly associated with ovulation and test strips for measurement in urine are very common. But LH can also provide important statements when it comes to the Polycystic Ovary Syndrome (PCOS) or masculinisation (virilisation). For this purpose the ratio between LH and FSH (follicle stimulating hormone) is calculated.

The GnRH test

For your gynaecologist, the luteinising hormone can provide information about a possible functional disorder of the endocrine system. Here, above all, an initial differentiation of the causes is made: During a GnRH test, the pituitary gland of the patient is stimulated with a synthetic gonadotropin-releasing hormone and LH and FSH are determined after a specified time. If both values increase, the cause is to be found in the superior hypothalamus. In this case it is unable to produce GnRH.

What is a normal LH value?

There is no normal value, such as blood sugar, when measuring hormones. The concentration of most hormones is subject to your so-called circadian rhythm. This means that the values fluctuate due to the day-night rhythm or seasonal conditions, for example. The female sex hormones are linked in a fixed way to the course of the female cycle and are responsible for healthy reproduction.

As described, LH is produced by the pituitary gland. The blood then serves as a transport vehicle to all target organs, therefore the hormone can be detected in blood but also in urine, since the values in urine correlate with the blood values. The measured results provide the current amount of LH provided by the pituitary gland.

The standard values of LH are divided into three cycle phases:

In the first phase of the cycle a result of 2 to 6 units per litre (U/L) is expected. The concentration during ovulation (ovulatory peak) is between 6 and 20 U/L. In the corpus luteum phase (luteal phase), the concentration of LH decreases again to values of 3 to 8 U/L. During menopause, however, measurement results of more than 30 U/L are normal. Different normal ranges also apply to men and children. Significant concentrations in children can only be measured after puberty. LH values in men vary between 0.8 and 8 U/L and are directly related to the level of testosterone.

When taking a blood sample to determine the LH level, it is important to hit the right time during the cycle- depending on what you want to examine. Rarely the measurement of the luteinising hormone alone is sufficient to obtain a sufficient statement in the context of fertility treatment (cycle monitoring) or for determining ovulation and both, the level of the results, and the normal ranges can vary considerably from laboratory to laboratory. For this reason, each measured value must be interpreted accordingly by the doctor performing the test. Measurement results deviating from the standard values can therefore only be classified as too low or too high in connection with the corresponding reason for examination.

If you want to monitor your LH hormone throughout your whole cycle, you can use the Pearl Fertility system to make sure you never miss a peak.

When is the LH value too low?

The cause of too low concentrations of both LH and FSH can be an impairment of the pituitary gland or hypothalamus: If the pituitary gland itself is affected, it may not produce enough LH. If the superior hypothalamus is unable to provide enough GnRH, LH production will also cease. Possible causes are tumours, injuries or environmental factors such as extreme sports or anorexia.

When is the LH value too high?

Even if the result of a laboratory test indicates that ovulation is imminent, it does not necessarily have to take place. A high LH value could also have its origin in polycystic ovary syndrome (PCOS). Elevated values can also occur in LUF ("luteinized unruptured follicle") syndrome. Especially in the context of fertility treatment, there is a probability of up to 25%. In LUF, LH and other hormones indicate ovulation, but the follicle does not burst. As a result, the egg cannot enter the fallopian tube- the LH concentration would therefore be considered too high for the clinical situation.

The causes here are still largely unexplained. (3,4) However, there are various indications that there is a connection between childlessness caused by LUF syndrome and the intake of non-steroidal anti-inflammatory analgesics (NSAIDs, for example painkillers). (5) Another study was able to show a correlation between women suffering from endometriosis and the LUF syndrome. (6)

If high LH and FSH levels are detected in the blood in the laboratory, the problem is almost certainly located in the ovaries themselves. If the ovaries do not function and therefore produce too few hormones (estrogen, progesterone), this is registered by the hypothalamus and the pituitary gland. As a result, they provide high levels of LH and FSH to stimulate the ovaries more.

If premature menopause or early puberty is suspected, the determination of LH can support the diagnosis. It should be noted that an increase in luteinising hormone can be the sign of a variety of possible causes of ovarian dysfunction. These must be clarified in advance if for example artificial insemination is planned.

Although rare, a high value can also be due to a measurement error. Sometimes very high HCG concentrations in the blood can simulate a false positive LH result. However, experienced laboratory staff are able to detect such difficulties in time.

[1,2]http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/hypopit/lhfsh.html

[3] Complete and partial luteinized unruptured follicle syndrome after ovarian stimulation with clomiphene citrate/human menopausal gonadotropin/human chorionic gonadotropin. Coetsier T, Dhont M. Human Reproduction. 1996;11(3):583–587. http://dx.doi.org/10.1093/HUMREP/11.3.583

[4] LUF-Syndrom, Häufig, selten oder nicht existent? M. Ludwig, B. Sonntag Springer Link, Gynäkologische Endokrinologie May 2010, Volume 8, Issue 2, pp 112–116

[5] Nonsteroidal anti-inflammatory drugs and reversible female infertility: is there a link? Stone S1, Khamashta MA, Nelson-Piercy C. Drug Saf. 2002;25(8):545-51.

[6] P-205 Basement membrane integrity is altered in the late secretory phase in women with endometriosis: implications for the pathogenesis of endometriosis Palial, K.K., Drury J., Heathcote L., Valentiji A., Farquharson, Gazvani R., Rudland, K. H., , Oxford Journal, Human Reproduction, 2011 26,suppl 1:202-223

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