Clinical Chemistry Blog Notes 03: GnRH

Gonadotropin-releasing hormone (GnRH)

Known as Luteinizing-hormone releasing hormone (LHRH), it is a tropic peptide hormone responsible for the release of FSH and LH from the anterior pituitary.

Control of FSH and LH

At the pituitary, GNRH stimulates the synthesis and secretion of the gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These processes are manipulated by the size and frequency of GNRH pulses, as well as by response from androgens and estrogens. Low frequency GNRH pulses lead to FSH release, whereas high frequency GNRH pulses stimulate LH release.

In GNRH discharge between females and males. In males, GNRH is secreted in pulses at a fixed recurrence, but in females the frequency of the pulses varies during the menstrual cycle and there is a large surge of GNRH just before ovulation.

GNRH flow is in all vertebrates, and is all-important for right generating function. a single hormone, GNRH1,command a complex process of follicular growth, ovulation, and corpus luteum support in the female, and spermatogenesis in the male.

GNRH action is very low during childhood, and is activated at puberty. During the generating years, pulse activity is critical for successful reproductive function as controlled by feedback loops. However, once a pregnancy is established.

GNRH in other organs

GNRH is found in organs outside of the hypothalamus and pituitary and its role in other life processes is poorly understood. For instance, there is likely to be a role for GNRH1 in the placenta and in the gonads.

(GnRH)

Its secretion aon ae onset of puberty triggers sexual development and from then on its movement for normal sexual physiology of both males and females. In both sexes, its secretion occurs in periodic pulses usually occurring every 1–2 hours.

Primary Effects Secondary Effects

FSH and LH Up estrogen and progesterone Up (in females)

Testosterone Up (in males)

Gonadotropin Releasing Hormone (GnRH) Test

Indication

To recognize hypothalamic-pituitary disease in advance and delayed puberty in both sexes in those children with low basal gonadotropins.

Contra-indications

This test may be performed simultaneously with TRH or glucagon as part of triple pituitary test.

Principle

GnRH (gonadotropin releasing hormone) is a weak secreted by the hypothalamus which stimulates the production and secretion of LH and FSH by the anterior pituitary.

Side Effects

GnRH may rarely cause nausea, headache and abdominal pain.

Preparation

no specific patient preparation is required.

Requirements

3 Lithium heparin tubes
GnRH the dose for children is 2.5 microgm/kg to a max 100 microgm

Procedure

time 0 min 2 mL blood for LH & FSH immediately give GnRH

time 20 min 2 mL blood for LH & FSH

time 60 min 2 mL blood for LH & FSH

Interpretation

* Normal basal reference values in prepubertal children are:
LH <>

* Following GnRH, the reaction may be considered normal if the basal values are in the reference range and there is at least a doubling at 20 min for LH and FSH. The response varies throughout the menstrual cycle: early (D4) <>

* An extreme response is seen in primary & secondary gonadal failure.

* A flat response in gonadotropins (<>

* The importance of the LH response is equal to the mean nocturnal LH and therefore the development of puberty.

LH test

Formal name: Luteinizing hormone
Related tests: FSH, Testosterone, Progesterone, Estradiol, Total estrogens

LH Test

How is it used?

LH is commonly used in combination with other tests (FSH, testosterone, estradiol and progesterone) in the workup of infertility in both men and women. LH levels are also useful in the investigation of menstrual changes and to help in recognize of pituitary disorders or diseases involving the ovaries or testes.

A urine test may be used to detect the surge in LH that indicates that development will occur in the next 1-2 days.

In children, FSH and LH are used to diagnose delayed and childhood.

LH is measured in relation to gonadotropin releasing hormone (GnRH) to tell difference between primary or secondary disorder of the hypothalamic-pituitary axis. GnRH is the hormone produced by the hypothalamus that activates the pituitary to release LH and FSH. this test, a baseline blood sample is drawn and then the patient is given an injection of GnRH. After blood samples are drawn at specified times, and the level of LH is measured. This test can help characterized between disease of the ovaries or testes and a disorder of the pituitary or hypothalamus. It is also often applicable in the evaluation of advance or delayed puberty.

FSH test

Formal name: Follicle-stimulating hormone
Related tests: Total estrogens, Estradiol, LH, Testosterone, Progesterone

How is it used?

FSH is often used in combination with other tests (LH, testosterone, estrogen, and progesterone) in the workup of infertility in both men and women. FSH levels are used to help conclude the reason a man has a low sperm count. FSH levels are also useful in the detecting of menstrual irregularities and to aid in the examination of pituitary disorders or diseases involving the ovaries or testes. In children, FSH and LH are used to diagnose delayed or childhood.

In women, FSH and LH levels can help to tell the difference between failure of the ovaries themselves and failure of the ovaries due to disorders of either the pituitary or the hypothalamus). Increased levels of FSH and LH are fixed with primary ovarian deficiency.

When a woman enters menopause and her ovaries stop working, FSH levels will rise.

Low levels of FSH and LH are constant with secondary ovarian deficiency due to a pituitary or hypothalamic problem.

In men, high FSH levels are due to primary testicular failure. This can be due to developmental defects in testicular growth or to testicular injury.