TRIPTORELIN (GnRH)

Triptorelin description

Decapeptide Triptorelin ((D-Trp6)-GnRH)) acts as an agonist analog of endogenous peptide hormone Gonadotropin-releasing hormone (GnRH), thus reversibly repressing of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). It is a potent GnRH receptor agonist. After chronic, continuous administration, Triptorelin effects sustained decreases in LH and FSH production and testicular and ovarian steroidogenesis. Serum testosterone concentrations may fall to levels typically observed in surgically castrated men. It was patented in 1975 and approved for medical use in 1986. Animal studies comparing triptorelin to native GnRH found that triptorelin had 13 fold higher releasing activity for luteinizing hormone, and 21-fold higher releasing activity for follicle-stimulating hormone.

GnRH mechanism of action

After secretion from the GnRH secreting neurons in The hypothalamic preoptic area, GnRH is transported by the blood via the hypothalamic-pituitary-gonadial axis to the pituitary gland, which contains gonadotropic cells, with GnRH responsive receptors – a seven-transmembrane G-protein-coupled receptor named Gonadotropin releasing hormone receptor (GnRHR). The binding of GnRH to GnRHR subsequently activates in the pituitary gland the synthesis and secretion of gonadotropins – luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These processes are controlled by the size and frequency of GnRH pulses, as well as by feedback from androgens and estrogens. Low-frequency GnRH pulses lead to FSH secretion, while high GnRH pulses stimulate LH release. GnRH is degraded by proteolysis within a few minutes.

GnRH results of action

There are differences in GnRH secretion between females and males. In males, GnRH is secreted in pulses at a constant frequency; however, in females, the frequency of the pulses varies during the menstrual cycle, and there is a large surge of GnRH just before ovulation. GnRH secretion is pulsatile in all vertebrates, and is necessary for correct reproductive function. Thus, a single hormone, GnRH1, controls a complex process of follicular growth, ovulation, and corpus luteum maintenance in the female, and spermatogenesis in the male. GnRH also affects various sexual behaviors. Elevated GnRH levels lead to increased libido and sexual activity in women. In men, an increase in GnRH induces a sharp increase in testosterone levels, accompanied by all of its typical strong anabolic and androgenic effects.

Hypogonadotropic hypogonadism

Hypogonadism is a condition in which the male testes or the female ovaries produce little or no sex hormones. Hypogonadotropic hypogonadism (HH) is a form of hypogonadism that is due to a problem with the pituitary gland or hypothalamus. HH is caused by a lack of hormones that normally stimulate the ovaries or testes. These hormones include gonadotropin-releasing hormone (GnRH), follicle stimulating hormone (FSH) and luteinizing hormone (LH). There are several possible causes of HH such as damage to the pituitary gland or hypothalamus from surgery, injury, tumor, infection, or radiation; genetic defects; high doses or long-term use of opioid or anabolic steroids; high prolactin level (a hormone released by the pituitary); severe stress; long-term (chronic) medical diseases, including chronic inflammation or infections; or drug use..

Triptorelin mechanism of action and results

Triptorelin binds to Gonadotropin releasing hormone receptor (GnRHR) in the pituitary gland and stimulates secretion of gonadotrophins – Luteinzing hormone and Follicle-stimulating hormone. This causes an initial phase of LH and FSH stimulation, prior to down-regulation of the gonadotrophin-releasing hormone receptors, thereby reducing the release of gonadotrophins in the long term, which in turn leads to the inhibition of androgen and estrogen production. The effects of triptorelin can usually be reversed once the drug is discontinued.

Pharmacodynamics of Triptorelin

The first administration of triptorelin is followed by a transient surge of follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol and testosterone. The time, peak and decline of testosterone in the body varies depending on the dose administered. This initial surge is often responsible for worsening of prostate cancer symptoms such as urethral or bladder outlet obstruction, bone pain, spinal cord injury and hematuria in the early stages. A sustained decrease in FSH and LH, and significant reduction of testicular steroidogenesis is usually seen 2-4 weeks post-initiation of therapy. This result is a reduction of serum testosterone to levels which are typically seen in surgically castrated men. Ultimately, tissues and functions that require these hormones become inactive.

Triptorelin field of use

Primary indications include endometriosis, for the reduction of fibroids, for prostatic cancer, and to treat male hypersexuality with severe sexual deviation. Triptorelin is used to treat prostate cancer (PCa) as part of androgen deprivation therapy (ADT). After a transient increase, continuous administration of triptorelin results in downregulation of LH and FSH levels followed by a suppression of ovarian and testicular steroid biosynthesis. In the United Kingdom is Triptorelin used for hormone replacement therapy to suppress testosterone or estrogen levels in transgender people (in conjunction with estradiol valerate for trans women or testosterone for trans men). But Triptorelin has been also used as a chemical castration agent for reducing sexual urges in sex offenders.

Scientifically investigated possible benefits of Triptorelin

• • Treatment for prostate cancer (PCa) as part of androgen deprivation therapy (ADT)
  • Use in reproduction medicine, endometriosis, central precocious puberty

Triptorelin possible side-effects 

• • Hot flashes (a sudden wave of mild or intense body heat), sweating, or clamminess
  • Mood changes such as crying, irritability, impatience, anger, and aggression
  • Injection site irritation (pain, swelling, or itching)
  • Headache, nausea or dizziness
  • Decreased sexual ability or desire
  • Leg or joint pain
  • Breast pain
  • Depression

GnRH and Triptorelin FAQ

Can be Triptorelin used to treat prostate cancer in men?

Yes, Triptorelin can be used to treat advanced prostate cancer in men. Most types of prostate cancer need the male hormone testosterone to grow and spread. Triptorelin works by reducing the amount of testosterone that the body makes. This effect helps slow or stop the growth of cancer cells and helps relieve symptoms such as painful/difficult urination.

What stimulates GnRH?

GnRH is a hormone produced in the hypothalamus region of the brain. GnRH moves through the bloodstream and Hypothalamic–pituitary–gonadal axis to the pituitary gland. There, it binds to ist natural receptors Gonadotropin releasing hormone receptor (GnRHR). Those receptors signal the pituitary gland to create Luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

What promotes the release of GnRH in the body?

Kisspeptin signals directly to the hypothalamic GnRH neurons via the kisspeptin receptor to release GnRH into the portal circulation, which in turn stimulates the anterior pituitary gonadotrophs to produce LH and FSH.

What inhibits GnRH release?

The GnRH neurons are regulated by many different afferent neurons, using several different transmitters (including norepinephrine, GABA, glutamate). For instance, dopamine appears to stimulate LH release (through GnRH) in estrogen-progesterone-primed females; dopamine may inhibit LH release in ovariectomized females. Kisspeptin appears to be an important regulator of GnRH release. GnRH release can also be regulated by estrogen. It has been reported that there are kisspeptin-producing neurons that also express estrogen receptor alpha.

Does testosterone inhibit GnRH?

YES: A negative feedback system occurs in the male with rising levels of testosterone acting on the hypothalamus and anterior pituitary to inhibit the release of GnRH, FSH, and LH. Testosterone and/or its metabolites slows LH pulse frequency in man and inhibit LH and FSH secretion presumably by an effect on the hypothalamic GnRH pulse generator, but it also may have a direct action on the pituitary.

What are Gonadotropic cells?

Gonadotropic cells are endocrine cells in the anterior pituitary that produce the gonadotropins, such as the follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Release of FSH and LH by gonadotropes is regulated by gonadotropin-releasing hormone (GnRH) from the hypothalamus.

What are the two Gonadotropic hormones?

Luteinizing and Follicle Stimulating Hormones. Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are called gonadotropins because stimulate the gonads – in males, the testes, and in females, the ovaries.

What is the HPG axis?

HPG axis – the hypothalamic–pituitary–gonadal axis refers to the hypothalamus, pituitary gland, and gonadal glands as if these individual endocrine glands were a single entity. The HPG axis plays a critical part in the development and regulation of a number of the body’s systems, such as the reproductive and immune systems. Fluctuations in this axis cause changes in the hormones produced by each gland and have various local and systemic effects on the body. The axis controls development, reproduction, and aging in animals. Gonadotropin-releasing hormone (GnRH) is secreted from the hypothalamus by GnRH-expressing neurons. The anterior portion of the pituitary gland produces luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and the gonads produce estrogen and testosterone.

Does GnRH cause weight gain??

Suppressing sex hormone levels with gonadotropin-releasing hormone (GnRH) agonist therapy may cause fat gain.

How does GnRH reduce estrogen?

Gonadotropin releasing hormone agonists (GnRH) are a type of medication that suppresses ovulation by stopping the production of estrogen and progesterone. In order for this axis to function properly and result in ovulation, GnRH has to be released in a pulsatile fashion.

What is the function of Gonadotropic hormone?

Gonadotropin-releasing hormone causes the pituitary gland in the brain to make and secrete the hormones luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In men, these hormones cause the testicles to make testosterone. In women, they cause the ovaries to make estrogen and progesterone.

Triptorelin dosage

Usual adult dose for medical purposes in the treatment of prostate cancer (to downregulation of LH and FSH levels, reduction of serum testosterone and suppression of testicular steroid biosynthesis): An injection of 3.75 mg of triptorelin is usually given every 4 weeks, an injection of 11.25 mg of triptorelin is usually given every 12 weeks, or an injection of 22.5 mg of triptorelin is usually given every 24 weeks. When used in children with central precocious puberty: An injection of 22.5 mg of triptorelin is usually given every 24 weeks.

Any people are also discussing the ability of Triptorelin to restore testosterone production in cases of hypogonadotropic hypogonadism, for example caused by high doses or long-term use of anabolic steroids (called PCT – post-cycle therapy). If it is contemplated to use triptorelin to restore testosterone production, then 100 mcg of triptorelin should be injected subcutaneously or intravenously as a single dose and only once (because another doses or long-term administration of triptorelin contrary results in downregulation of LH and FSH levels followed by a extreme suppression of testosterone production).

Triptorelin should only be administered by a healthcare provider, and when used, the response to this drug should be monitored with LH levels, basal LH, or serum concentration of sex steroid levels during therapy as necessary.

Overview

Triptorelin is analogue of endogenous peptide hormone Gonadotropin-releasing hormone (GnRH). It is a potent GnRH receptor agonist. Triptorelin binds to Gonadotropin releasing hormone receptor (GnRHR) in the pituitary gland and stimulates secretion of gonadotrophins – Luteinzing hormone and Follicle-stimulating hormone. This causes an initial phase of LH and FSH stimulation, prior to down-regulation of the gonadotrophin-releasing hormone receptors, thereby reducing the release of gonadotrophins in the long term, which in turn leads to the inhibition of androgen and estrogen production. Primary indications include endometriosis, for the reduction of fibroids, for prostatic cancer, and to treat male hypersexuality with severe sexual deviation. Triptorelin is used to treat prostate cancer (PCa) as part of androgen deprivation therapy (ADT). Triptorelin should only be administered by a healthcare provider and response to this drug should be monitored during therapy.