Letrozole Review | Buy Letrozole Liquid
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Letrozole is an antiestrogen that is an orally active, nonsteroidal and selective third-generation aromatase inhibitor. It was first discovered in the 1980’s by swiss scientists screening compounds for their aromatase inhibiting abilities.
It inhibits the formation aromatase from producing estrogens by binding itself to the heme of its cytochrome P450 unit in a competitive and reversible manner. It is weakly protein bound and has a large volume of distribution (approximately 1.9 L/kg).
During the final stage of estrogen biosynthesis, aromatase catalyzes the aromatization of androstenedione and testosterone into estrone and estradiol.
Letrozole has a specific form of action and does not reduce production of corticosteroids.
Structure of Letrozole
Letrozole is an order less white or yellowish crystalline powder which is freely soluble in dichloromethane, slightly soluble in ethanol, and insoluble in water.
Mechanism of Action
When tested on adult non tumor and tumor bearing female animals, letrozole is as effective in decreasing uterine weight, elevating serum LH, and causing the regression of estrogen-dependent tumors. In contrast to ovariectomy, letrozole does not cause an increase in serum FSH. Letrozole selectively inhibits gonadal steroidogenesis but does not significantly affect adrenal mineralocorticoid or glucocorticoid synthesis.
Letrozole inhibits the aromatase enzyme by totally binding to the heme of the cytochrome P450 subunit of the enzyme, this causes a reduction of estrogen biosynthesis in all tissues. Studies on female rats indicate that letrozole significantly lowers serum estrone, estradiol and estrone sulfate and has not been shown to significantly affect adrenal corticosteroid synthesis, aldosterone synthesis, or synthesis of thyroid hormones.
Further tests on animal subjects shows that letrozole is rapidly and completely absorbed from the gastrointestinal tract, rate of absorption is not affected by food. The major clearance pathway is through renal excretion of the glucuronide conjugate from a slowly metabolized inactive metabolite. About 90% of radiolabeled letrozole is recovered in urine.
Letrozole has a terminal elimination half-life of about 2 days. Steady-state plasma concentration after administration of a daily 2.5 mg dose to animal subjects is achieved in 2-6 weeks. There is a slight non-linearity in the pharmacokinetics of letrozole upon daily administration of 2.5 mg, which is indicated by plasma concentrations at steady state which were 1.5 to double what was predicted from the concentrations measured after a single dose.
These steady-state levels were observed to be maintained over extended periods without the occurrence of continuous accumulation of letrozole.
Letrozole Uses
This compound is used in the treatment of hormone receptor positive or unknown receptor status breast cancer postmenopausal females.
It is also used in the induction of ovulation and treatment of early stage gynecomastia. Studies have also shown letrozole to delay the fusing of the growth plates in mice. Studies have also shown letrozole to be useful when combined with misoprostol in pretreatment for pregnancy termination.
Letrozole for gynecomastia
Research shows that gynecomastia occurs when there is an increase in the circulating and/or local breast tissue ratio of estrogen to androgen, it is also caused by increased aromatase activity and decreased testosterone. Letrozole proved effective in the treatment of male rats with gynecomastia as a result of its antiestrogenic and aromatase inhibiting properties.
Letrozole vs Clomid
Clomid had always been the first option for ovulation induction in unexplained fertility for its ease of use and cheapness. Although repeated use led to thinning of the endometrium, or the blood lining of the uterus. Letrozole stimulates ovulation without these side effects by working in a different manner with less chance of multiple gestation.
Recent studies show that letrozole led 18.7% success while clomid lead to 23.3%. There isn’t a significant difference between the effectiveness of the pair but letrozole does not cause thinning of the endometrium when used repeatedly.
Where to buy letrozole
Letrozole for sale can be purchased at Loti Labs. The compound is sold in a concentration of 2.5mg per ml. Letrozole purchased from Loti Labs meets the highest US quality standards by passing through testing by high power liquid chromatography (HPLC) and mass spectrometry.
References
1.Simpson ER (2003). “Sources of estrogen and their importance”. The Journal of Steroid Biochemistry and Molecular Biology.
2. Biljan MM, Hemmings R, Brassard N (2005). “The Outcome of 150 Babies Following the Treatment With Letrozole or Letrozole and Gonadotropins”. Fertility and Sterility.
3. Vivian Chi Yan Lee; Ernest Hung Yu Ng; William Shu Biu Yeung; Pak Chung Ho (2011). “Misoprostol With or Without Letrozole Pretreatment for Termination of Pregnancy”. Obstetrics & Gynecology.
