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Tamoxifen is a non-steroidal selective estrogen receptor modulator (SERM). It has been shown to exert both agonist and antagonist activity at the estrogen receptors. Furthermore, it has been shown to activate heat shock protein. It is an FDA-approved drug prescribed for the treatment of breast cancer in men and women. It also has an off-label indication for the treatment of gynecomastia and infertility. Various studies indicate tamoxifen can increase muscle strength, leading to its ban by the World Anti-Doping Agency. Currently, it is being studied for its effect on myotubular myopathy and other types of cancers. At Pinnacle Peptides, tamoxifen for sale is exclusively available for research and experimentation.

From Pubchem

IUPAC Name: 2-[4-[(Z)-1,2-diphenylbut-1-enyl]phenoxy]-N,N-dimethylethanamine
Synonyms: trans-Tamoxifen, Crisafeno, Diemon
Molecular Formula: C26H29NO
Molecular Weight: 371.5 g/mol
CAS number: 10540-29-1
PubChem CID: 2733526

It was first developed by a chemist named Dora Richardson in 1962 when she was trying to discover a compound that could work as a birth pill. Later, the researcher discovered that it induces ovulation instead of preventing pregnancy. Initially, it was approved for the treatment of fertility but it never proved useful in human contraception.

Back then, another scientist named Walpole convinced the company he was working with to test the drug for its effect on breast cancer. In 1971, the first human clinical study on tamoxifen showed promising results, leading to its development for the treatment of breast cancer. Ultimately, it was first approved by the FDA for advanced breast cancer treatment in 1977.

Tamoxifen is an estrogen receptor modulator and it has been shown to exhibit both estrogenic and antiestrogenic activity. It acts as an antagonist in the breast tissues and competitively binds to the estrogen receptor (ER). By blocking the hormone activity, it prevents ER binding to estrogen-response elements on DNA. This, in turn, slows down the cellular response to estrogen and decelerates the progression of the cell cycle.

In the bone tissues, it acts as an agonist of estrogen receptors. Instead of blocking estrogen receptors, it activates them and might prevent osteoporosis through this mechanism. Furthermore, it has been shown to exhibit agonist activity at the estrogen receptors present in the hypothalamus of premenopausal women, thus facilitating ovulation [1].

1. X-linked Myotubular Myopathy

Myotubular myopathy, also known as X-linked myotubular myopathy (XLMTM), is a fatal congenital disorder resulting from mutations in the myotubularin gene. Its symptoms include generalized hypertonia and muscular weakness that often leads to neonatal mortality. Animal studies show promising results about the therapeutic effects of tamoxifen on histological and pathological abnormalities associated with myotubular myopathy. Furthermore, tamoxifen has been shown to offer positive outcomes such as increased life expectancy, improvement in overall motor function, hindrance of disease progression, and prevention of lower limb paralysis [2].

2. Tamoxifen resistance

Tamoxifen has been a go-to drug for the treatment and prevention of breast cancer. However, its long-term use has developed resistance over time and it is no longer a preferred drug. Studies show that anastrozole shows more promising results and better compliance in treating breast cancer as compared to tamoxifen.

Literature suggests that the mechanism behind the resistance to tamoxifen has been associated with the excessive activation of the PI3/AKT/mTOR pathway and downregulation of estrogen receptors. Furthermore, the CD63+ CAF (cancer-associated fibroblasts) subset plays an important role in the resistance to tamoxifen. CD63+ CAF is present in the microenvironment of breast cancer cells. One study found that inhibitors of CD63+ CAF have been shown to enhance the effect of tamoxifen [3].

3. Gynecomastia

Gynecomastia is characterized by the enlargement of breast tissue. It is often caused by a disturbance in the levels of estrogen and progesterone. Tamoxifen has been used for the treatment of gynecomastia for years. A 10-year cohort study concludes that tamoxifen therapy improves symptoms of gynecomastia in every 9 out of 10 patients [4].

Furthermore, research suggests that it is a safe and effective option for pubertal gynecomastia. To achieve optimal results, tamoxifen therapy should be initiated when the disc diameter is ≥3 cm and treatment should be continued for a minimum of 6 months [5].

4. Male Infertility

Research shows that tamoxifen might improve sperm density. One study was conducted to check the effect of tamoxifen on sperm motility, morphology and density. Subjects either received 10mg tamoxifen or a placebo two times a day for three months. The researchers found that tamoxifen reduced the number of dead spermatozoa and increased sperm density as compared to the control group [6].

5. Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a neuromuscular disorder that is characterized by progressive degeneration of muscles. It is often caused by a mutation in the DMD gene present on the X chromosome. Research suggests that tamoxifen is involved in the regulation of calcium homeostasis and might manage symptoms of DMD. One study in a mouse model of DMD found that tamoxifen treatment relieved motor fatigue and improved muscle strength [7].

Tamoxifen is a selective estrogen receptor modulator. It acts as an antagonist to estrogen receptors in breast tissues and reduces the proliferation of cancer cells. Research shows that it improves pathological conditions associated with myotubular myopathy and increases muscle strength in mouse models of DMD. Further, research is ongoing to confirm tamoxifen’s effect on these disorders. We don’t support its unwarranted use and offer liquid tamoxifen purchase exclusively for research and experimentation. Only buy tamoxifen if you are a licensed researcher.

1. Farrar MC, Jacobs TF. Tamoxifen. [Updated 2023 Apr 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.
2. Gayi, E., et al., Tamoxifen prolongs survival and alleviates symptoms in mice with fatal X-linked myotubular myopathy. Nature Communications, 2018. 9(1): p. 4848.
3. Gao, Y., et al., CD63+ Cancer-Associated Fibroblasts Confer Tamoxifen Resistance to Breast Cancer Cells through Exosomal miR-22. Advanced Science, 2020. 7(21): p. 2002518.
4. Mannu, G.S., et al., Role of tamoxifen in idiopathic gynecomastia: A 10-year prospective cohort study. The Breast Journal, 2018. 24(6): p. 1043-1045.
5. Sabancı, E., et al., Tamoxifen Treatment for Pubertal Gynecomastia: When to Start and How Long to Continue. Breast Care, 2023. 18(4): p. 249-255.
6. Kotoulas, I.G., et al., Tamoxifen treatment in male infertility. I. Effect on spermatozoa. Fertil Steril, 1994. 61(5): p. 911-4.
7. Nagy, S., et al., Tamoxifen in Duchenne muscular dystrophy (TAMDMD): study protocol for a multicenter, randomized, placebo-controlled, double-blind phase 3 trial. Trials, 2019. 20(1): p. 637.