Your mileage may vary: Trans women and erectile function

One common question asked by trans women considering hormone therapy is how this may affect their ability to have penetrative sex. Antiandrogens and estrogen can impair erectile function, reducing spontaneous erections, responsiveness to sexual arousal, and nocturnal erections — an effect noted by treatment protocols and guidelines. However, the extent of that impairment can be unpredictable for a given individual. Among communities offering advice on transition, a variety of folk wisdom on how this can affect trans women’s experience of sex has proliferated, with maxims such as “your mileage may vary”: you won’t know its effects on you for certain without finding out firsthand.

As it turns out, a study of hormone therapy and erectile function in trans women confirms the “YMMV” phenomenon. Bettocchi et al. (2004) studied 25 trans women on HRT, nearly all of whom had low or undetectable levels of testosterone, and conducted numerous tests of their erectile function. This allowed researchers to identify any correlations between hormone levels and trans women’s ability to become erect. Interestingly, no correlation was found between testosterone levels and sexual function self-reported on a questionnaire:

Questions 2 and 4 of the IIEF-15 questionnaire were used for subjective determination of EF and the results are reported in Table 1. To determine whether or not hormonal depletion had caused subjective changes in EF, all patients were asked to state if they would have scored the same or better in IIEF questions 2 and 4 just before hormonal treatment. Interestingly, all of them reported their EF before hormonal depletion being comparable to their EF at the time of our evaluation. …

Serum levels of morning total testosterone were found to be normal (4.5–8.5 ng/ml) only in the patient treated with finasteride, low (1–4.4 ng/ml) in 10 patients and undetectable (<1ng/ml) in 14 patients. As shown in Table 1, testosterone levels did not correlate with IIEF scores (P-value 0.7 for question 2 and 0.4 for question 4).

Additionally, the results of Doppler ultrasonography of their erections, after pharmacological stimulation with injection of prostaglandin E1, showed no correlation with their testosterone levels:

Penile CDU after pharmacological stimulation yielded normal results (PSV >35 cm/s, RI >0.9, erection score 4–5) in all patients, suggesting no correlation between pharmacologically induced erection and testosterone levels. Interestingly, the erection score was always upgraded after the period of manual genital stimulation, thus providing further information on the role of sexual stimulation in this group of patients.

However, when occurrence of nocturnal erections was measured, this was found to be significantly correlated with testosterone:

The NPT test was performed for two consecutive nights with the Rigiscan Plus device (Dacomed, USA) and considered normal in the case of recording of at least four erectile events per night lasting at least 30 min, an increase in circumference ≥2cm at the base and ≥2 cm at the tip, and maximal rigidity at both base and tip ≥60%. …

The NPT test, conversely, yielded normal results in 12 patients, equivocal (sporadic, ie less than 4 rigid events per night) in seven, and pathologic (no rigid events at all) in six. Interestingly, NPT test results were strictly related (P<0.006) to serum testosterone levels (Table 1).

Nocturnal erections play an important role in maintaining penile health in cis men. Dr. Tobias Köhler has stated that frequent nighttime erections keep penile tissue stretchy and pliable, whereas absence of these erections can lead to shortening of the organ over time:

“Your penis is a ‘use it or lose it’ organ,” says Dr. Köhler.

Frequent erections—say, multiple times a night—keep your penile tissue soft and stretchy, Dr. Köhler explains.

They also prompt the smooth muscle in your penis to relax, which allows the blood to rush in and get you hard.

It’s important this happens often, because the stretchiness of your penis decreases if the smooth muscles stay contracted for too long, Dr. Köhler says. Without a regular relaxing-contracting workout, the length of your erect penis may actually shorten.

Given the observed effect of blocking testosterone on nocturnal erections and the role they play in maintaining penis size, the reduction in frequency of these erections may account for the long-term shrinkage and atrophy experienced by many trans women on HRT. 

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About Zinnia Jones

My work focuses on insights to be found across transgender sociology, public health, psychiatry, history of medicine, cognitive science, the social processes of science, transgender feminism, and human rights, taking an analytic approach that intersects these many perspectives and is guided by the lived experiences of transgender people. I live in Orlando with my family, and work mainly in technical writing.
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One Response to Your mileage may vary: Trans women and erectile function

  1. Pingback: Trans people soared in the 2010s. But theres still work to do – Sports News

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