Enarei

Estrogen monotherapy

Estrogen monotherapy is an alternative to antiandrogen medication (testosterone blockers) that uses only estradiol to stop the body’s production of testosterone (and other androgens like DHT). It is widely used by trans people who take DIY hormone therapy, and occasionally used in formal healthcare settings.

Estrogen monotherapy avoids the drawbacks of antiandrogens, and can therefore be much safer, but may require higher dosages of estradiol than normally recommended to successfully block testosterone production, which can increase the risk of problems such as blood clots (Aly, 2020).

In practise, only modestly higher estradiol levels seem to be needed for successful testosterone suppression using estrogen monotherapy: where traditionally, estradiol levels in the 100 - 200 pg/mL (367 - 734 pmol/L) range are targeted, estrogen monotherapy may instead require levels of roughly 100 - 300 pg/mL (367 - 1101 pmol/L) (Langley et al., 2021; Aly, 2021).

Key points

  • May avoid the drawbacks of antiandrogens
  • May require higher estradiol dosages to successfully block testosterone
  • May carry a higher risk of complications such as blood clots at high dosages

Dosing

There is no standardized dosing for estradiol monotherapy, and only limited data is available.

Estrogen patches have been shown to suppress testosterone as effectively as GnRH analogues at a dose of 300 - 400 μg, with median estradiol levels of 230 pg/mL (844 pmol/L) (Langley et al., 2021).

Estrogen injections may require estradiol levels of approximately 100 - 300 pg/mL (367 - 1101 pmol/L) based on literature analysis (Aly, 2021).

Risks & management

Oral (swallowed) estradiol pills carry a greater risk of blood clots than other forms of estrogen. As a result, estrogen monotherapy using estradiol pills is unlikely to be safe or effective (Langley et al., 2021; Mohammed et al., 2015; Olié, Canonico, & Scarabin, 2010; Leinung, Feustel, & Joseph, 2018).

With any form of estrogen, the risk of problems such as blood clots rises with higher dosages. When using estrogen monotherapy, it is therefore still important to avoid unnecessarily high estradiol levels; for example, those in excess of 300 pg/mL (1101 pmol/L). (Aly, 2020).

See also

References

  • Aly. (2020). Estrogens and Their Influences on Coagulation and Risk of Blood Clots. Transfeminine Science. [URL]
  • Aly. (2021). An Informal Meta-Analysis of Estradiol Curves with Injectable Estradiol Preparations. Transfeminine Science. [URL]
  • Langley, R. E., Gilbert, D. C., Duong, T., Clarke, N. W., Nankivell, M., Rosen, S. D., Mangar, S., Macnair, A., Sundaram, S. K., Laniado, M. E., Dixit, S., Madaan, S., Manetta, C., Pope, A., Scrase, C. D., Mckay, S., Muazzam, I. A., Collins, G. N., Worlding, J., Williams, S. T., … Parmar, M. (2021). Transdermal oestradiol for androgen suppression in prostate cancer: long-term cardiovascular outcomes from the randomised Prostate Adenocarcinoma Transcutaneous Hormone (PATCH) trial programme. Lancet (London, England), 397(10274), 581–591. [DOI:10.1016/S0140-6736(21)00100-8]
  • Leinung, M. C., Feustel, P. J., & Joseph, J. (2018). Hormonal Treatment of Transgender Women with Oral Estradiol. Transgender health, 3(1), 74–81. [DOI:10.1089/trgh.2017.0035]
  • Mohammed, K., Abu Dabrh, A. M., Benkhadra, K., Al Nofal, A., Carranza Leon, B. G., Prokop, L. J., Montori, V. M., Faubion, S. S., & Murad, M. H. (2015). Oral vs Transdermal Estrogen Therapy and Vascular Events: A Systematic Review and Meta-Analysis. The Journal of clinical endocrinology and metabolism, 100(11), 4012–4020. [DOI:10.1210/jc.2015-2237]
  • Olié, V., Canonico, M., & Scarabin, P. Y. (2010). Risk of venous thrombosis with oral versus transdermal estrogen therapy among postmenopausal women. Current opinion in hematology, 17(5), 457–463. [DOI:10.1097/MOH.0b013e32833c07bc]