differenceblog, posts by tag: testosterone - LiveJournal

Advanced age and female sex are risk factors for osteoporosis, a bone disease characterized by decreased bone density. Sex hormones play an important role in bone health: levels of estrogen or testosterone seem to regulate the replacement of cells in mature bones. Eriksen et al (1988) first reported the presence of estrogen receptors in mature bones. Lower levels of sex hormones can lead to decreased bone density. The effect of lowered testosterone seems to be less severe than that of lowered estrogen. The reason for this difference is unclear: Moggs et al (2003) state that there is "no sexual dimorphism in receptor distribution" in bones.

Thomas et al (2001) found a relationship between body fat and bone mineral density (BMD) for women, but not men. However, Thomas found that bioavailable estradiol predicted BMD equally in men and women, pre- or post-menopause.

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I can think of three reasons why women have a greater risk of osteoporosis, despite the fact that aging lowers sex hormones in both men and women. First, women's estrogen levels typically drop post-menopause, while men's testosterone levels decline more slowly. Second, the effect of the estrogen drop seems to be more severe. Third, women live longer. They're around more to suffer the effect. Still, with my non-standard hormone distribution, I do worry about the health of my bones. There simply isn't enough research into the long-term side effects of cross-sex hormone therapy. Dr. Nick Gorton's Medical Therapy and Health Maintenance for Transgender Men: A Guide For Health Care Providers gives a great review of what little is known.

Androstenone, a testosterone derivative present in sweat and urine, can smell very differently (or not at all) to people depending on a single gene, according to Keller et al (2007). It is, of course, stronger in men's sweat and urine. Some smellers report a "sweet, floral" odor, while others report a more logical "sweaty, urinous" odor, and some can not detect the scent at all. Twin studies two decades ago (e.g. Wysocki & Beauchamp, 1984) implicated a genetic component to this ability, but Keller's study found a strong effect of a single gene. Dorries et al (1989) suggest that most, if not all, children are able to detect androstenone, but that this ability decreases with age, and is more likely to decrease in men. Brand and Millot's review (2001) confirms that many studies find that women are more sensitive to androstenone than men, but that men are more likely to find the smell pleasant.

Because some mammals use androstenone to communicate social signals, many consider the variation in human sensitivity "intriguing." Leslie Vosshall, one of the co-authors of Keller's study, asks "what happens to humans who can't get the signal because they have the nonfunctional copy of the gene? Or the hyperfunctional one? What could be the social and sexual implications of this on one's perception of the smell of fellow humans?" (RU News, 9/16/07)

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As I have mentioned with no small amount of embarassment before, I'm a smoker. The fact that I can smell anything amazes and concerns me. In the past, when I have temporarily quit smoking, I've actually found the smells and tastes of the world to be fairly overpowering and largely unpleasant -- however, I recognize that my continued smoking makes me overpowering and unpleasant to a lot of people. *shrug*

I bring this up because, even with my senses dulled by smoking (and possibly by testosterone, but I'm not sure), I still get a very strong sense of "my people" or "not my people" when I meet someone. Traditionally, I've identified it as "they smell right" or "they smell wrong." Discussing this sense, I've encountered other people who say they smell people as "right" or "wrong" -- and they are all women. (Granted, my n is 3 or 4)

Judy Skatssoon (6/4/2007), writing for news.com.au, says that the University of Warwick has "dealt heterosexual women a final indignity." Skatssoon is referring to research by Michael Tlauka that found differences in mental rotation ability, with straight men scoring the highest while straight women scored the lowest. However, although the news articles attribute this work to Tlauka, the paper published in April's Archives of Sexual Behavior was published by Maylor et al (2007).

Tlauka et al (2005) tested men and women with paper and computer maps in a virtual store, and found that men required less time and made fewer mistakes than their female counterparts. Martin et al's 2007 review of the effect of testosterone and estrogen finds that gender differences in spatial ability are "large and robust."

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Mental rotation tasks (MRT) are probably one of my favorite topics because they really do seem to consistently break down by gender. The fact that Maylor et al found that ability appeared to vary by sexuality (determined by self-identification, on an internet survey) continues to tie sexuality and gender together in a way that I politically deny and inwardly fear may be true. Research that classifies by sexuality often seems to suggest that lesbians are more "manly" and gay men more "womanly" than their straight counterparts. I don't know what to make of it, but it feels to me as if they are asking the wrong questions.

Cognitive testing on people undergoing transgender therapy is rare, but has happened on a few occasions. The Netherlands seem to be the source of much of this research. Van Goozen et al (1995) found differences in spatial and verbal ability in both female-to-male and male-to-female transsexuals after just three months on hormone therapy. Hulshoff Pol et al (2006) performed MRIs on transsexuals before and after 4 months on hormones (but before any surgical intervention). This group found structural changes towards normal for the patient's new sex; "The magnitude of this change (i.e. 31 ml over a 4-month period) is striking, since it signifies a decrease in brain volume, which is at least ten times the average decrease of around 2.5 ml per year in healthy adults." In contrast, Haraldsen et al (2005, Norway) did not find any differences between transsexuals and birth-sex-matched controls on six sex-sensitive areas of cognitive testing, pre-hormones or at 3 and 12 months into hormone therapy.

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I generally try to avoid using transsexual studies, because I'm dissatisfied with the controls. I'm not sure of an ethical way to do it, but I'd really like to see studies done with a non-treated transsexual control group. Most theories of transsexuality suggest that there are already differences between transsexual and non-transsexual males and females, and therefore it may not be appropriate to use non-transsexuals as a control group. One interesting confound noted by Haraldsen et al is the socio-economic difference between transsexuals and non-transsexuals in the US; transsexuals tend to have a higher socio-economic class, because it is mostly the people who can afford the rigorous and unsupported medical standards who present for transsexual treatment.

The Local (3/1/07) reports that Carina Bladh (Linköping, Sweden) was outraged to discover that her car insurance premium jumped up when her official sex changed from female to male. After her complaint, the insurer decided to lower her premium back to its prior level. According to Esurance's website (2007), in the U.S., gender only figures into insurance rates for drivers under 25, where men pay more.

As discussed in "A Driven Man" (11/27/06), men have been involved in more accidents than women over the history of automobile driving. J.J. Arnett's 2002 review repeats the frequently-stated suggestion that because testosterone is linked to aggression, and aggressive driving is linked to accidents, testosterone must be a contributing factor to frequency of traffic accidents. However, I've been unable to find any studies that actually connect testosterone levels to differences in driving behavior.

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I used to joke that I didn't transition until I was 25 because I didn't want my car insurance to go up. I've driven so much less since my transition that it's very hard for me to judge if my driving habits have changed. Just prior to transition, I had a job that required a 40 minute commute by car each way. Since transition, my only job has been easily accessible on public transportation, so I only drive about once a week, if that. I am not at all convinced that aggressive driving and other measures of aggression are similar enough to draw the kinds of conclusions that seem to be common in this research. It seems that aggressive driving is far more focused on the self vs. a system (e.g. "I need to get ahead of this traffic") whereas other types of aggression are more focused on the self vs. a specific other (e.g. "This guy spilled his drink on me").

Eva Emerson, in Medical News Today (2/11/07) reports on John Tower's (2006) model for explaining aging and the mortality gap between the sexes. Tower's work with drosophila (fruit flies) suggested that sexula differentiation might come at great cost in terms of aging. Mitochondria seem to be less functional in older fruit flies and mammals, with sex-specific effects. Yan et al (2004) found mitochondrial aging in monkey cardiac cells was accelerated in males compared to females. Vina et al (2006) suggest that estrogen may have a protective effect, by "up-regulation of longevity-associated genes." Ballard and Whitlock (2004 review) point out that much mitochondrial modeling at this point is speculative. Ballard and Whitlock discuss weaknesses in the current data, and in the generalizability of animal models to humans.

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I'm still baffled by the mortality gap. Women seem to be more prone to disease, yet outlive men on average. Social theories about fewer violent deaths or lower risk jobs make some degree of sense to me, but considering the other biological costs of accomodating pregnancy, the genetic theories just confuse me. On that note, any comments on my possible misinterpretation of today's results is welcomed.

However, I have to say that the phrase "[estrogen] cannot be administered to males because of its powerful feminizing effects" (Yan et al, 2006) caused me a bit of a chuckle. My male-to-female transsexual friends are constantly complaining about how ineffective estrogen is in comparison to testosterone, because estrogen supplements seem to achieve very little feminization without the complementary testosterone blockers, whereas my testosterone shots shut down my estrogen production on their own.

Burnham et al (2003) found that men in current committed relationships (whether married or unmarried) had 21% lower saliva testosterone levels than single men. Gray et al (2004) confirmed these results, and found that this effect was more pronounced in afternoon and evening samples of testosterone levels than in morning samples. However, it is not clear whether partnering causes lower T levels, or whether lower T levels increase the chance of partnering.

Van Anders and Watson (2006) found that single people with lower testosterone levels in Phase 1 of their study were more likely than high-testosterone subjects to be partnered at follow-up (6+ months later). Interestingly, van Anders and Watson also looked at testosterone levels in women, and took sexuality into account. They found that lower testosterone levels were associated with partnered status in heterosexual men, and non-heterosexual women, but not with heterosexual women or non-heterosexual men.

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I've been lucky enough to be in one stable, committed relationship since before I began injecting testosterone. This makes me fairly rare among the transmen I know. Transition is necessarily a stressful, self-absorbed period in a person's life, and this tends to make maintaining a relationship difficult. The suddenness of the hormonal changes (in the case of ftms, the simultaneous onset of menopause and second puberty) can make the most trivial interactions difficult, as well. Therefore, I doubt the effect of hormone administration on the relationships of transsexuals is a good comparison model for hormone levels in the general population.

Susman et al (1985) found that high-for-age sex hormone levels were linked to poor psychosocial outcomes for both adolescent girls and boys. Most studies of hormone effects on social interactions focus on this age group. Kershbaum et al (2006) compared saliva-measured testosterone levels in a group of 42 adolescents, and asked them to fill out evaluations of themselves and each other. Boys with high testosterone levels were considered to be leaders, but not likable, by their peers. Girls with higher testosterone were considered likable, but not leaders.

In adults, the results seem to be similar. Testosterone levels have often been linked to social status and success, but a review by Zitzmann and Nieschlag (2001) cautions against any broad interpretation of these results. In contrast, Cashdan (2003) found that high-estradiol women reported fewer competitive interactions over sports than women with lower levels, but most other competitive interaction measures were tied to androgens. While Cashdan does express different modes of aggression and competitiveness observed in her study (e.g. verbal aggression, overt competitiveness), she does not express whether any group was more or less socially successful as a result.

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I'd like to start by recommending the Zitzmann and Nieschlag review to anyone who is interested in the research on testosterone effects. It's very broad and cautious, but it covers a lot of interesting research, and I found it fascinating. Now, on to the anecdotal drivel! I was (like my mother and father) a late bloomer. I didn't reach menarche until I was 15.5 (putting me solidly in the upper 10% of that particular curve), and was still just developing secondary sexual characteristics in college. I felt like this really made my social development difficult in a number of ways, although being a smug little brat probably didn't help, either.

Although present in both men and women, DHEA levels are higher in men throughout life. DHEA is produced in the adrenal gland, and according to Quackwatch.com (2004) "no one knows exactly what it does in the body." DHEA is easily converted into testosterone and estrogen. A Mayo Clinic study (Nair et al, 2006) published today in the New England Journal of Medicine examined the effects of the sex steroid Dehydroepiandrosterone (DHEA) in elderly men and women. Despite health-food store and internet claims that DHEA is the "fountain of youth," Nair et al largely confirmed results of the French "DHEAge" study (2000) which showed that the only consistent effect of DHEA administration was to raise DHEA levels.

In terms of gender-specific responses to DHEA administration, results have been inconsistent enough that it is difficult to draw conclusions. The DHEAge study showed some increase in female (but not male) libido. Nair et al. reported bone mineral density increased in both men and women, but these were site-specific and different between the sexes. As Paul M. Stewart (2006) puts it in his editorial about Nair et al's study, BMD changes "have been small, specific to site and sex, and not reproducible between studies." Nair et al also found a slight decrease in HDL ("good" cholesterol) for men and women taken together, but no other lipid changes. Kudielka et al (1998) showed that DHEA treatment seemed to affect adrenal stress hormone levels in elderly women under social stress tests, but not in men. Kudielka et al's study did not show any reduction of subjective stress, however. Gurnell and Chatterjee's review (2001) suggested that DHEA's seeming effectiveness in women might be attributable to raising androgen levels above what would normally be expected in women, although (being pro-DHEA) they were quick to point out that the body hair and lipid level side effects had not been demonstrated as being present.

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My relationship to OTC hormones is largely influenced by my participation in the transsexual community. It seems like the question arises again and again in the female-to-male online forums: "will taking DHEA give me masculinizing effects?" Testosterone itself is schedule III controlled substance (like ketamine or codeine), with heavily restricted access and legal implications for unauthorized possession, which DrugPolicy.org says are rapidly increasing due to media attention. Therefore, a lot of transsexuals frustrated with the red tape attempt to jump-start their transition with "dietary supplements" -- an expensive and ineffective habit. I am somewhat heartened to see that most of the DHEA studies show no ill effect from the administration of DHEA, but I worry about what long-term effects may be looming in the future. However, this concern is probably biased, since the Mayo Clinic points out that long-term effects of the plain-old-testosterone therapy I take myself are largely unknown.

On the opposite side of the coin from yesterday's post about the effects of estrogen levels, testosterone levels also have distinct effects multiple functions. Interestingly, while Bhasin et al. (2001) found many physical performance changes related to testosterone levels in healthy young men, they did not find changes in sexual function, visual-spatial cognition, or mood. This is in contrast to Gray et al.'s 2005 study which did show dose-dependent changes in these factors for older men. These studies focus more on exogenous testosterone treatment, unlike studies of menstrual cycles, because the variations in testosterone levels seem more complex and less predictable. There seem to be several cycles which affect endogenous testosterone levels in males.

Reinberg and Lagoguey (1978) found peaks in plasma testosterone in the early morning and late evening, with a minor peak in the afternoon, although Plymate et al (1989) found that aging may blunt this peaking effect. Doering et al's 1975 study found a 20-22 day cycle in testosterone levels in 12 out of 20 volunteers. Smals et al. (1976) found that there were seasonal changes in testosterone levels as well, with levels peaking in the summer and autumn, and at their lowest in the winter and early spring. This is in addition to the normal reduction in bioavailable testosterone that Morley et al (1997) correlated with aging.

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My own testosterone levels are highly predictable, because more than 90% of my serum testosterone at any given time is artificially raised. Once a week, I inject 50mg of testosterone cypionate into my thigh muscle. This seems to be the dose that works best for me, although many female-to-male transsexuals (ftms) are on different doses. It is quite common for ftms to be treated on a 2-week cycle, while other ftms use a daily, topical treatment, which give them a much more stable testosterone level. I prefer injections for convenience and cost, but found that I couldn't handle the peaks and valleys. When my testosterone levels are low, I feel moody and lethargic. When they are high, I feel invulnerable. I notice the mood variations a lot less now than when I first began testosterone therapy; I have a couple of theories as why this might be, but no way of testing them. My suspicion is that I had to build up to a baseline with my small weekly doses, and that my valleys are not as deep as they were when I was first starting. However, I think it is more likely that I've simply become used to the shifts, and have found other ways to compensate.