Mesterolone is the trade name for the oral androgen mesterolone (1-methyldihydrotestosterone) from Schering (now Bayer). Similar to dihydrotestosterone, mesterolone is a strong androgen with weak anabolic activity. Like dihydrotestosterone, mesterolone is rapidly reduced to the inactive diol metabolite in muscle tissue, where concentrations of 3-hydroxysteroid dehydrogenase are high. The weak anabolic properties of this compound suggest a tendency to block androgen receptors in muscle tissue, and due to its extremely high affinity for plasma binding proteins such as SHBG, mesterolone may actually enhance the activity of other steroids by displacing a higher percentage of the compound with free testosterone in an unbound state. In the athletic population, mesterolone is primarily used to increase androgen levels during fat loss or in preparation for competition, and is also used as an anti-estrogen due to its inherent ability to antagonize aromatase.
Brand Names Proviron, Mesterolone, Mesviron
Androgenic Index 30-40
Anabolic Index 100-150
Measurement Testosterone Propionate
Chemical Name 17beta-hydroxy-1alpha-methyl-5alpha-androstan-3-1-methyl-5alpha-dihydrotestosterone
Estrogenic Activity None
Progestogenic Activity None
Structural Features of Mesterolone
Mesterolone is a modified form of dihydrotestosterone. It differs in that a methyl group has been added to the carbon group at the -1 position, which helps protect the hormone from liver metabolism during oral administration. The same structural modification is also used in the oral Primobolan. Alkylation at the first position slows liver metabolism of the steroid during absorption, although not nearly as much as c-17 alpha alkylation. Although the overall bioavailability is still much lower than that of c-17 alpha alkylated oral steroids, Mesterolone is resistant enough to breakdown to achieve adequate blood levels for adequate dosing. Mesterolone also has a very strong binding affinity for the sex hormone binding globulin SHBG, which may displace other steroids that bind more weakly to SHBG into the free (active) state.
Side Effects of Mesterolone (Estrogenic)
Methadone does not aromatize and is not converted to estrogen. There is no need to worry about transestrogenicity or water storage when using this steroid.
In fact, it is thought that Mesterolone may act as an anti-aromatase in the body, thereby preventing or slowing the conversion of steroids to estrogen. Its effects may be somewhat comparable to Arimidex.
Side Effects of Mesterolone (Androgenic)
Methadone is an androgenic steroid, and androgenic side effects are common with this compound, especially at high doses, which may include oily skin, acne, and body/facial hair growth. Anabolic/androgenic steroids may also exacerbate male pattern hair loss. Women also need to be warned of the potential side effects of anabolic/androgenic steroids: these may include deepening of the voice, menstrual irregularities, changes in skin texture, facial hair growth, and clitoral enlargement. In addition, 5-alpha reductase does not metabolize mesterolone, so its non-androgenic properties are not affected by finasteride.
Side Effects of Mesterolone (Hepatotoxicity)
Methadone is not c17-alpha alkylated and therefore does not produce hepatotoxic effects.
Side Effects of Mesterolone (Cardiovascular)
Anabolic/androgenic steroids may have a detrimental effect on serum cholesterol. This includes a tendency to lower HDL (good) cholesterol values and increase LDL (bad) cholesterol values, which may shift the HDL to LDL balance toward a greater risk of atherosclerosis. The relative effects of anabolic/androgenic steroids on serum lipids depend on dose, route of administration (oral or parenteral), type of steroid (aromatizable or non-aromatizable), and degree of resistance to hepatic metabolism. Mesterolone is an oral non-aromatizable androgen that has negative effects on lipids. Studies of hypogonadal men taking 100 mg of mesterolone daily for approximately 6 months have shown significant increases in total cholesterol (18.8%) and LDL cholesterol (65.2%), while HDL cholesterol has been significantly reduced (-35.7%).
To help reduce cardiovascular strain, it is recommended to maintain a regular aerobic exercise program at all times during dosing and to minimize saturated fat, cholesterol, and simple carbohydrate intake. Supplementation with fish oil (4 grams per day) and natural cholesterol/antioxidant formulas such as products such as lipid stabilizers are also recommended.
Side Effects of Mesterolone (Testosterone Suppression)
Mesterolone has a very weak inhibitory effect on gonadotropins and serum testosterone. Studies have shown that when given at moderate doses (150 mg per day or less), testosterone levels are not significantly suppressed. However, in studies of high doses (300 mg per day or more), the drug strongly suppresses serum testosterone.
How to Use Mesterolone (Male)
To treat androgen insufficiency, Mesterolone is usually taken at the beginning of treatment at a dose of 1 tablet (25 mg) 3 times a day. Later, the drug is continued at a lower maintenance dose, which is usually 1 tablet (25 mg) 1 to 2 times a day. It is often used in combination with other fertility drugs (such as injectable FSH) to maintain male fertility.
In male athletes, the usual dose is 50 mg to 150 mg of Mesterolone per day, and the drug is taken in cycles of 6-12 weeks.
Many bodybuilders like to use Mesterolone during a fat loss phase or competition preparation, especially when used with anabolic drugs such as Winstrol, Anavar, or Primobolan, which are relatively low in androgen content. Mesterolone can effectively adjust the ratio of androgens to estrogens upward, thereby increasing muscle hardness and density, increasing libido, and increasing the efficiency of burning body fat. It is also commonly used (at similar doses) to prevent breast development in women, often in conjunction with Nolvadex tamoxifen 10-20 mg daily.
How to Use Mesterolone (Women)
Mesterolone is not approved for use in women. The drug is not recommended for women who wish to enhance their physique or athletic performance due to its strong androgenic properties. However, some women do like the drug and find that a 25mg tablet daily is enough to effectively change the hormonal balance in the body, greatly affecting body size changes. In such cases, intake is usually limited to no more than four to five weeks to minimize the chance of lasting toxic effects. One 25mg tablet of Mesterolone per day combined with 20mg of tamoxifen can more effectively build muscle, thereby making the body more inclined to burn off excess body fat, especially in specific areas such as the hips and thighs. However, it should be used with extreme caution.