All of us know how important hormones are and the vital role they play in transferring signals and information from one set of cells to another. They are secreted by one of the glands that make up the endocrine system. GnRH is one such hormone that is produced in the hypothalamus (a part of the endocrine system) region of the brain.
Isolated in the early 1970s, GnRH (gonadotropin-releasing hormone) is said to be one of the earliest of hormones to be synthesized and released within the hypothalamus. The credit of discovery goes to two Nobel laureates Guillemin and Schally.
GnRH or Gonadotropin-Releasing Hormone (Triptorelin): Product Information
GnRH is a poly peptide that is made up of 10 amino acids and is important for the production of sex hormones in the body. From the hypothalamus, it moves into the bloodstream and reaches the pituitary gland and gets attached to certain receptors. Once this happens, it triggers the gland to produce two more hormones: LH (luteinizing hormone) and FSH (follicle-stimulating hormone). These are known as the gonadotrophic hormones, which stimulate the reproductive organs to secrete Testosterone, estrogen, and progesterone.
GnRH Mechanism of action
FSH stimulates the growth of eggs in the ovaries and also leads to the production of estrogen and in males, LH stimulates the production of testosterone. When estrogen is produced, it signals the pituitary gland to make more LH and release FSH more slowly. LH is responsible for the mature egg being released by the ovary. When ovulation results, there is a drop in both the hormones.
Thus we see that GnRH governs the sexual physiology of men and women. However, the GnRH secretion is different for both. GnRH secretion is pulsatile, that is- the frequency at which it is secreted varies. In males, this is secreted at a constant frequency, whereas in females the frequency varies during the menstrual cycle and just before ovulation, the production of GnRH increases.
Pharmacokinetic and other information
Since GnRH is associated with the production of sexual hormones, it is not very active during childhood; however once puberty or adolescence is reached and the reproductive period begins, it gains momentum and plays an important role in the reproductive function. It again becomes inactive when a woman becomes pregnant and activity is also disrupted when the hypothalamus and pituitary glands dysfunction.
The Biochemical Process
Many neurons and neuro transmitters are involved in the regulation of GnRH neurons. Some help in the stimulation and inhibition of LH release. That is why GnRH is essentially considered a neuro- hormone.
GnRH Antagonists and Agonists
No sooner than Guillemin and Schally discovered GnRH, they tried to modify the peptide to help stimulate and block variants for various procedures– the result was a new avenue of therapy with GnRH antagonists and agonists.
GnRH agonists and antagonists belong to a group of hormone drugs called GnRH analogues. These analogues are used in infertility treatment. The use of GnRH agonists is a big advancement in hormone therapy and is used to stop the production of testosterone and estrogen. GnRH agonist injections are given every day—these force the pituitary gland to stop producing hormones.
GnRH antagonists are very similar to the naturally occurring hormone GnRH that is made in the hypothalamus, but as the name suggests it has an antagonistic effect. Like GnRH it is also a peptide molecule that is made up of many amino-acids. When it binds to the GnRH receptors, it prevents GnRH from going into action. As a result it blocks the release of LH and FSH in the pituitary glands, thus suppressing the production of testosterone and estrogen. This is invaluable during fertility treatments, especially when preparing for in-vitro fertilization, when it is needed to control the amounts of LH and FSH. GnRH antagonists are usually administered in the form of an intramuscular or subcutaneous injection.
Shutting down the pituitary gland is essential to proceed with an infertility procedure.
Although the end result is the same, the GnRH antagonists and agonists work slightly differently. While the GnRH antagonist ensures an immediate drop in LH and FSH production, GnRH agonists take some time before they bring about a drop in the secretion of LH and FSH.
After the discovery of GnRH, any research that was done was directed toward treating infertility, but with synthetic GnRH proving to be rather resourceful, the focus of diagnosis and treatment was turned toward endocrine disorders and cancer.
Other potential medical uses of GnRH
Recently there have been newspaper reports that the hypothalamus plays a role in aging and researchers were focusing on the effect of GnRH on aging. Scientists found that it was possible for GnRH to reach the brain from the periphery, indicating that the hormone could have some anti-aging properties. Of course this does require additional study, but the prospects do seem exciting.