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Levothyroxine T4 refers to a synthetic chemical that mimics the natural chemical thyroxine. Thyroxine is secreted by the follicular cells within the thyroid. Scientists are attempting to perfect an artificial version of this hormone as a means of treating thyroid deficiencies or cancers in animals in the future.

Currently, research into the development of levothyroxine T4 largely focuses on addressing the symptoms of hypothyroidism. Some studies have implied that this chemical could be used to manage goiter because it has been shown to lower the presence of thyroid-stimulating hormone in animal subjects.

However, the application of this chemical must be taken with care as test subjects that were exposed to this chemical long-term showed a variety of negative side effects including decreases in bone mineral density.

Effects on Hypothyroidism on the Testes of Mature Rats

The study hoped to investigate the effects of propylthiouracil (PTU) on rat testes compared to the treatment regimens of zinc and levothyroxine.

• A group of 20 sexually mature albino rats were exposed to PTU for two weeks to make the subjects hypothyroidism.

• The effects of PTU on the testicular function were studied using histopathological methods after the unilateral orchiectomy performed on day 15 of the study. Treatments were evaluated using serum thyroid-stimulating hormone and the zinc levels on the first day, after one week and on day 15.

• After this administration, the rats were divided into five groups that would be given lr3 igf1 or zinc for a total of 15 days.

Those treated with levothyroxine saw a decreased tubular diameter, thickening of the basal membrane and interstitial oedema in the hypothyroidic testicles. After the treatment was completed the testicular histology and the spermatogenesis would gradually recover in all of the groups that were given hypothyroidism.

Those that were given a combination of levothyroxine and zinc sulphate saw the greatest increase in improvement levels, which implies that zinc may have an effect on testicular function.

Effect on Rat Skeletal Muscle Resistance Arteries

This study investigates the idea that hormones would have vasodilatory effects on the body of the subjects and attempts to determine if such effects would be endothelium-dependent.

• Skeletal muscle in rats and the resistance arteries of around 100 microns were dissected to measure the vessel diameter changes by using a video-detection system.

• Each vessel was then pre-constricted using thromboxane to measure the percentage of dilation after the exposure of increasing concentrations of levothyroxine or triiodothyronine. Dialation in response to triiodothyronine was measured after the endothelial denudation.

• The measurements indicated that triiodothyronine had a greater effect on the rat test subjects than levothyroxine.

These results indicate that thyroid hormones cause direct vasodilatory effects in body endothelium-dependent and endothelium-independent components. These results imply that that these hormones can have direct vasodilatory effects which can partially account for the cardiovascular actions these hormones have when a rat has hyperthyroidism or when the chemicals were administered pharmacologically during cardiac surgery.

Given the current risk of side effects associated with the application of levothyroxine T4 in animal test subjects, this chemical is not yet approved for use in human subjects or in a clinical setting.

Sources:

http://onlinelibrary.wiley.com

http://www.anesthesia-analgesia.org/content/85/4/734.short

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Letrozole is an aromatase inhibitor that may have benefits in managing hormonally-responsive breast cancer in animals. In scientific studies it has been indicated that letrozole may be used for ovarian stimulation because it has fewer side effects than Clomiphene Citrate and fewer changes of causing multiple gestation. Some studies indicate that letrozole may have a lower risk of birth defects in lab rats than chemicals applied for similar purposes.

Studies have also focused on letrozole as a potential option to address gynecomasstia if this disease is in the early stages of treatment, as well as a potential way to manage spermatogenesis.

However, it is important to note that this chemical should not be used outside of a scientific setting and is not yet approved for use on humans or studies on humans.

Influence on Complexation and Hydroxybutenyl-beta Cyclodextrin

• This study worked to examine the in-vitro effects of three various CDs on the chemical letrozole because this chemical is insoluble in water.

• This study indicated that the most promising chemical, hydroxybutenyl-beta cyclodextrin could be used in-vivo in both male and female rats in spite of the fact that letrozole has dramatic gender-based difference when applied as a pharmacokinetic.

• The terminal half-life of the chemical letrozole in male rats is 11.5 while it is 42.3 in female rats.

• Creating a more complex chemical by combining letroxole with the HBenbetaCD helps to improve oral absorption in male rat subjects and helped to maximize the abortion in female rat subjects. In both genders, the presence of HBenbeta CD helped to improve in-vivo rates of absorbtion.

When letrozole was applied in the rat test subjects in capsule form the HBenbetaCD, presence resulted in a higher absolute oral bioavailability. This implies that the solubility limits in the extent and rate of letrozole absorption exist for male rats, but are not limited in the rate of absorption for female rats.

Induced Polycystic Ovaries in the Rat

• This study attempted to develop new models in animals for the study of what’s known as polycystic ovaries by using aromatase inhibitor letrozole(non-steroidal).

• Thirty-four rats were taken as subjects and divided into a control group and three test groups of 10 rats each. Each of these treatment groups were given concentrations of letrozole in .1, .5 and 1 mg respectively. The chemical was administered to the rats once a day for 21 days.

• Throughout the testing period, the rats were collected for vaginal spears and estrus cycle determination. On the subsequent day letrozole administrations, the rats were killed and the ovaries and uteri were weighed and excised while serum hormone levels in the ovaries were examined.

• Compared to the rats in the control group, the ovaries in the study groups had a higher incidence of subcapsular ovarian cysts with capsular thickening with incomplete luteinization. A decreased number of corporea lutea was also seen.

These results are not fully convincing in the study of polycystic ovaries or PCOS. However, this is a vital step in developing an animal model that could be used to study polycystic ovary syndrome in humans without the need for human test subjects.

Letrozole is still in the testing phase. There are no approved doses or applications of this chemical that are approved for use in humans or outside of a research setting.

Sources:

http://www.ncbi.nlm.nih.gov/pubmed/17637172

http://www.ncbi.nlm.nih.gov/pubmed/15010188

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GHRP-6 is a peptide which comprises the AA sequence of H-His-D-Trp-Ala-Trp-D-Phe-Lys-NH2. In studies GHRP-6 has shown biological actions similar to the naturally occurring hunger stimulating peptide ghrelin.

GHRP-6 contains D-amino acids that are entirely synthetic, lacks opioid activity, and shares no sequence relation with GHRH.

It has also been shown that GHRP-6 can lead to re-stimulation of the natural production of GH.

Studies have shown that GHRP-6 increases the secretion of IGF-1 by the liver of some lab rats (Insulin-Like Growth Factor 1), which is speculated to be a required component in the anabolic mechanisms leading to the action of GH. It also appears that GHRP-6 has positive implications for the central nervous system, as ghrelin is known to protect neurons.

What may be the most interesting aspect of ghrelin (and therefore GHRP-6) is the huge variety of roles it plays in biological functions. It is involved in processes in lab rats that include appetite regulation, cardiac functions, gastrointestinal functions, metabolism of carbohydrates, and even has some behavioral effects.

GHRP-6 fills many of ghrelin’s roles, but does not fill all of them. It has been largely shown to focus on the release of GH. Of all synthetic peptides, GHRP-6 is the most ghrelin-like.

When ordering GHRP-6, be sure to choose a research company that:

• Provides MS and HPLC reports on its products.

• Has the ability for large scale production thereby lowering cost and improving efficiency.

• Is committed to customer satisfaction and customer service.

Settle for nothing less than the best in quality peptides.

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