It is called the GnRH or LHRH (LH Releasing Hormone) test and is generally performed in adolescent subjects to check for any hormonal disorders that occur during puberty. But in many cases it may also be required for adult patients. What the GnRH
test is for The GnRh test is performed above all to investigate the cause of any hormonal irregularities and the relative dosage of luteinizing hormone (LH). In adults, ovarian or testicular activity, usually insufficient, may be measured. In children, doctors may prescribe testing to understand the cause of early or delayed puberty. What is luteinizing hormone
LH or luteinizing hormone is directly related to the release of eggs from the ovary. While in men it can be associated with the production of testosterone. Generally, to get a broader picture of the situation, the specialist also requires other tests such as those relating to the dosage of progesterone, estradiol and FSH. The amount of LH can also be assessed on days when the woman should be in the mid-cycle – that is, during ovulation – to measure the luteinizing hormone during its peak. Hypothalamic or pituitary disorders
In order to verify if the basis of ovarian or testicular irregularities there may be problems related to the hypothalamus or the pituitary, the luteinizing hormone (LH) is calculated as a consequence of the response of GnRh, acronym for Gonadotropin Releasing Hormone. This, under normal conditions, is produced by the hypothalamus by stimulating the pituitary to secrete LH and FSH (gonadotropins). The test can detect the presence of primary or secondary hypogonadism.
- In depth: hormones in relation to age
The hormones LH and FSH are absent in the child and begin to be produced shortly before puberty, when the FHS is superior to the luteinizing hormone. If the patient is healthy, the relationship is reversed after development. The two gonadotropins, in essence, are the mechanism that triggers the actual puberty and the reproductive capacity.
When the GnRH test is prescribed
Your doctor may request the test for several reasons: for example if infertility is suspected in men or women – especially if too low testosterone levels (in men) are associated with it. If there is a pattern of amenorrhea or irregular menstruation, when there is no normal (early or late) pubertal development or there is some age-related abnormality: excessive growth of the breasts, testicles or penis and growth of hair around the genital organs in childhood. Finally, it can also be requested in case of suspected – and early – menopause, or of abnormal symptoms linked to a hormonal imbalance: weight loss, inappetence, chronic fatigue. How is the GnRH test performed
First, a blood sample is performed which determines the blood concentration of the hormone. Thereafter, 200 mg of synthetic LHRH, the analogue of natural GnRH, is administered intravenously. The patient will not be able to leave the analysis laboratory because samples will be taken again: generally within two hours. The first after 15 minutes; the second after 30; the third after 60; the fourth after 90 minutes and the fifth after two hours.
- Deepening: Gonadotropin deficiency and infertility
Man can begin to have a correct production of sperm thanks to the secretion of FSH, while LH helps synthesize testosterone through the testicles. It goes without saying that when there is a deficiency in gonadotropins, an infertility problem can occur, while an increase can lead to serious testicular damage.
Preparation for the GnRH test
For the preparation for the test, no special precautions are generally required. Although it is a blood test, fasting is not necessary. It is good to say that the doctor may request that some medications be stopped which could affect the results. These include anticonvulsants (increase LH) and oral contraceptives which may lead to decreased gonadotropin. GnRH, the normal values
​​When a subject is healthy, intensity peaks are recorded 15 to 30 minutes later for luteinizing hormone and 30 to 60 minutes for FSH. Normal LH values ​​fall within a 30% to 100% increase from baseline, while FSH values ​​range from 10 to 50%. Gonadal changes
In the presence of gonadal changes the basal values ​​of LH (30-40 mu / ml) and FSH (45-55 mU / ml) are already high, with increases of three to four times already after thirty minutes. These values ​​could indicate an ovarian hypoplasia in progress, a gonadal dysgenesis or Turner syndrome. Elevated Luteinizing Hormone
When only Lh hormone is elevated and FSH is normal it could be polycystic ovary syndrome. Baseline values ​​are around 20-30 mU / lm and increase up to 4 times after 30 minutes. If both have increased, it could be menopause with very high basal values ​​of 50-80 for LH and 80-120 for FSH.
- Alterations
Ovarian deficiency: increased LH and FSH
Hypothalamic deficiency: decreased LH and FSH
Pituitary deficiency: increased LH and decreased FSH
Hyperprolactinaemia: slightly increased LH and FHS
Premature puberty: increased FSH and LH
Causes of Premature Puberty
In some cases it could be due to trauma or brain surgery, but also inflammation or tumors of the central nervous system. If it is pseudopuberta there could be testicular tumors, adrenal and ovarian cysts. It could also be testotoxicosis or McCune-Albright syndrome. Scientific Bibliography
[1] MedLine Plus – US National Library of Medicine
[2] Evaluation of GnRH analogue testing in diagnosis and management of children with pubertal disorders. Hemchand K. Prasad, Vaman V. Khadilkar, Rahul Jahagirdar, Anuradha V. Khadilkar, and Sanjay K. Lalwani.
