The Incredable Shrinking Brain…

As I’ve noted before, the brain responds to sex hormones.  Androgens tend to cause the brain to grow larger.  It appears that the absence of androgens in males, allows the brain size to shrink to closer to female norms over time.  In fact, such changes can occur quite rapidly.  Significant changes occur in the volume of the hypothalamus.

Lawrence has already critiqued two earlier studies of sexually dimorphic brain structure in (or near, depending on definition) the hypothalamus, in which she questions the author’s assertion that the BSTc is sexually dimophic and is an organizational effect (“locked in” during development) and is sex-reversed in transsexuals.  Lawrence argues strongly that this could not possibly be an organizational effect, since the BSTc is not sexually dimorphic until adulthood.  These studies were conducted in connection to a group of subjects from the Nederlands, with a common author, Dick Swaab.  Here I would like to explore a more recent study involving the very same subjects, joined by a few additional subjects, of another area, the hypothalamic uncinate nucleus, which is known to be sexually dimorphic.  Again, Swaab and his co-author claim this is not only sex reversed, but is again, to some degree, an organizational effect.  I question this conclusion, based on an analysis of their data.

Interestingly, the authors seem to have responded to Lawrence’s criticism regarding including only “Non-Homosexual” transsexuals in their study, in that in this third paper, they include categorization of the subjects into Blanchard’s two groups, “Homosexual” and “Non-Homosexual”.  All of the subjects that were in the earlier two studies are now either clearly identified as “Non-Homosexual” or “Not known”.  Only one new subject is identified as “Homosexual”.  As Lawrence notes, we can infer the likelihood of the not knowns as being “Non-Homosexual” based on the age at which they transitioned, as indicated by when they began HRT.  The youngest “Not known” is 36.  This strongly suggests that they are all “Non-Homosexual”.

The authors also categorized the subjects by “GID type: onset“.  For the life of me, I can’t imagine what meaning this has, as they list a subject who began treatment at age 64 as “early”, and even one who never sought any treatment at all, who died at age 84, as “early”.  I suspect this is a reference to self-reported awareness of their gender dysphoria.

This study uses a group of men who were castrated as part of treating prostate cancer as controls for reduction in circulating androgens, which is a better control group than the previous studies used.

If we accept, uncritically, the analysis of the authors, there appears to be a significant difference between the castrated men and the MTF transsexuals, while at the same time, no difference between the MTF transsexuals and natal females.  However, there is a catch, a BIG CATCH !

When one is studying these anatomic details of the brain, we are not simply slicing and dicing the brain and recording how big a clearly differentiable nodule of the brain is.  Actually, these parts of the brain are largely indistinguishable to the casual observer.  In order to even see these structures, one applies various stains to the thin slices of neural tissue where one hopes to find the structure in question.  These first slices are done literally blind, based on the distances from anatomic landmarks from maps of the “average” human brain.  Sometimes, they miss!  (It’s only about the size of a grain of sand.)  And sometimes, the stains don’t “take”.  And even when the stains do take, the boundaries between the clump of nerves of interest, and the surrounding nerves are often very, very fuzzy!  It takes an experienced bio-technician, working very carefully, to trace the boundary using computer software of photos of the region in question.  To get an idea of how difficult this can be, please examine the photos included in the paper.  Honestly, can you clearly tell where the borders are?  I sure can’t.

So, here’s the catch… Swaab and his co-author have chosen to include those subjects where they couldn’t identify the nucleus in question.  They give the numerical volume of the missing nucleus as “zero”.  This is akin to a school teacher misplacing a pupil’s exam paper and giving that student a score of “zero”!  An assertive student would then argue that they could also be given a score of 100%, given that the teacher can’t prove that they got any of them wrong.  Giving a missing data point a numeric value is very questionable.

Why do I argue that this is questionable?

Note that this makes several of the data groups bimodal, with a cluster at some non-zero value, and a cluster at zero, for each group that had such missing data.  This skews the mean downward.  The authors argue this is an acceptable analysis, noting that the MTF and natal female groups have approximately the same number of subjects in which they couldn’t identify the nucleus.  However, note that one of the control males also had no identifiable nucleus.  Are we to accept that such a bimodal distribution is real?  I don’t.

So, if we throw out these null results, given that we can’t reasonably give them a numerical volumetric value, is there still a significant difference between the groups?  Once again, we note that there is no difference between the MTF and natal female data.  But now, there is also no difference between these two groups and those men who were castrated!

Simply put, the data clearly shows that though the hypothalamic uncinate nucleus of the average MTF transsexual is the same as natal female, after years of HRT, so is that of castrated non-transsexual men.  Thus, the data clearly shows that this is purely an activational effect, and in no way gives us any clues as to the etiology of MTF transsexuals.

Addenda 3/2/2010

If the size of the INAH3 is an activational effect of the absence of androgens in the MTF transsexuals, it would follow that the time spent on HRT might correlate with the size.  It was always possible that it happens too fast to be in the useful time window of this data set, but I plotted the data anyway, just to see what would happen.  Interestingly it looks like the shrinkage of the INAH3 takes on the order of years, as suggested by this graph:

For more essays on trans-brains see Brain Sex.

References:

Hulshoff Pol, H. E., Cohen-Kettenis, P. T., Van Haren, N. E., Peper, J. S., Brans, R. G., Cahn, W., et al. (2006). Changing your sex changes your brain: Influences of testosterone and estrogen on adult human brain structure. European Journal of Endocrinology, 155(Suppl. 1), S107-S114.
http://eje-online.org/cgi/content/full/155/suppl_1/S107

Garcia-Falgueras A, Swaab DF. A sex difference in the hypothalamic uncinate nucleus: relationship to gender identity. Brain. 2008
http://brain.oxfordjournals.org/cgi/reprint/131/12/3132

 

Do as I say, not as I do…

…or in this case, believe what I say, not what I do.

The God Jupiter pretending to be the Goddess Diana to seduce / rape Callisto

One of the constant complaints of those who disagree with the two type taxonomy is that sexologists ignore their narratives, which would “prove” their theories wrong.  Of course they do… because they aren’t interested in their narratives, but in what they actually do!

What is of academic interest to researchers, becomes a matter of the ability to navigate a difficult social landscape, with the occasional land-mine, for the feminine androphilic transsexual.  If I may share with you a personally painful episode in my own life?

One day, back in ’76, when I was but eighteen years old, my roommate, Stella, also eighteen years old, and I were hosting our friends Jennifer, nineteen years old, and Marcella, twenty-four years old.  Our place was a tiny, cramped, poorly furnished studio apartment, hot in the summer, cold in the winter.  The four of us were very poor and still pre-op.  As Jennifer was a beautician, she was helping the others remove unwanted facial hair by waxing, while the three of them good humoredly bitched and complained in envy that I did not need to deal with such,  (I never grew a beard, no facial hair, just girl like, transparent vellus).  None of us could afford electrolysis yet, of course.  As we talked about our boyfriends, sex, and such… Jennifer abruptly exclaimed in a horrified tone, “Did you know that Karen is really bisexual?”

I knew in that instant what was coming next… Jennifer then told of how Karen had tried to seduce her in a very inappropriate manner!  I flashed back a few months…

Kay Brown in college

The household I had been temporarily sheltered in, with several older women, all lesbian ( save for one who we would today recognize as a “noho transman” / transmasculine who had bound his breasts to live as a man for several years but had detransitioned, who joshed me, occasionally trying to flirt with me, knowing I was only into men) was disbanding.  I needed a new place and I didn’t have much income, being dependent on a very meager remittance from my family.  The remittance came with the proviso that I was to stay far enough away from them such that I wouldn’t accidentally be seen by my family’s social connections, so as not to embarrass them.  This meant that I couldn’t seek to live with any of my high school friends.

Karen, a twenty-five year old recently post-op transsexual I had met at the Stanford Gender Dysphoria Clinic only days before eagerly sought me as her roommate.  She had a nice, but very small, apartment and her own car.  She consistently represented herself as a straight woman, looking for Mr. Right.  I felt safe enough accepting her invitation.  Living with her was OK at first, but I noticed that she was insanely jealous of my boyfriends.  At first I thought that that was the result of her not having any… So I hosted several parties, inviting available young men, straight, but open minded.  But… she ignored efforts at flirtations from cute guys… and flatly rebuffed several date invitations by these men.  This seemed odd and confusing.  Then, one very early weekend morning, while I was still in bed, Karen tried to seduce me, insisting on having sex with me or she would throw me out… which is exactly what she did when I very strenuously refused her!  Karen became irrationally angry and verbally abusive.  Further, while yelling at me, she balled both of her (rather large) fists and threatened me with them.  I feared for my safety.  I was out on the street that very morning!

In tears and very distraught, I had to beg my mother for assistance, since I was flat broke with no where to go.  She was very annoyed, but found and paid for first and last month’s rent of the small studio mentioned earlier.  I had been corresponding with Stella, since being given her contact information by the Stanford program, when I asked them if there was “anyone else like me?”  Stella moved from her parents home in a small town to become my roommate a couple weeks later, sharing expenses.  So, I guess it all worked out “OK”, but…

I listened to Jennifer’s story of being embarrassed by Karen, then recounted my own story, beginning “She isn’t bisexual”, which horrified my listeners even further.  I admitted I didn’t understand how this could happen… and we all began to discuss about the “older transsexuals” and how odd they seemed to be.  It was the much more world-wise Marcella who explained it all, “They are all TVs that need a bigger fix!”  We discussed it further and pieced Karen’s story together.  She had transitioned recently, starting HRT and had SRS only six months later at a clinic in the mid-west, near where her folks lived.  Her folks had paid for it in cash.  That clinic was known for only performing SRS on “true transsexuals”, which meant that Karen had to lie about being interested in men, hiding her real interest in women.  But, somehow, that medical lie had become a social lie… or maybe more accurately, a part of her established personal narrative, her self-image.  However, that was not her actual sexuality.  She was totally uninterested in men, focusing on women, or more likely those males who looked and acted like women, namely feminine androphilic transsexuals.  In the next few years that I saw her around in the community, she deliberately sought out the society of the feminine androphilic TS, while continuing to represent herself as straight (androphilic).  Whether she was ever successful in her efforts to find an HSTS lover, I can’t say.

So, there we were, three young transies (as we called ourselves back then) learning from our older and wiser mentor.  Marcella taught us how to survive, how to date straight boys who didn’t know we were TS without them discovering that we were pre-op; which straight night-clubs would let us in without carding us; and most importantly, giving us a working understanding of how autogynephilia operated, though we didn’t use that word, since that wasn’t even coined until a decade later.  We learned how to differentiate AGP TS and “our kind”… because this wasn’t a matter of academic interest, it was potentially a matter of survival… but certainly one of social necessity.  We learned how to spot an AGP TS by the way she walked, talked, held her body, what interests she had… and most especially, to trust our gut, which was invariably right.  If we felt that we were talking to a girl, she was like us… if we were getting mixed signals… she was AGP.

In recounting the above story, I know that I am risking offending many.  This is not my intention.  But this is the simple truth.

Further Reading:

Essay on Gynadromorphophilia (specific attraction to transwomen)

Essay on Gynandromorphilia and Autogynephilia / CrossDreaming

Essay on “Misplaced Moralizing” by gender critical’ individuals and the true meaning of “rapey”

This is your brain; This is your brain on hormones…

Your brain is like a muscle:  Use it or lose it… and it responds to sex hormones, which are really “growth hormones”, but with specific areas of the body that are targets for sexually dimorphic development.

In exploring the possibility that transsexuals may have a “brain sex” that is similar to their preferred gender identity, we are also stepping into the realm of gender politics in general.  What is the difference between men and women?  Is there a significant difference between them?  Once upon a time, in pre-feminist days, the early 19th Century, scientists supported the then prevailing view that women’s’ minds were inferior to men.  Proof of such was found in the measurable fact that women have, on average, smaller brains than men.  Of course, women also, on average, are both shorter and weigh less, so really, was this difference in brain size a significant one?  Then, came a more unbiased age (relatively speaking) in which it was shown that women and men have similar mental abilities, similar intelligence, and most importantly, similar potential for intellectual achievement.  Thus, came an age where to suggest that men and womens’ brains might differ in significant ways, was academically unpopular.  But nagging differences were still found… in animals.

In animal research, one could side step sexual politics, as well as ethical problems of experimenting on humans.  In animals, in the early to mid-20th Century, it was found that sex hormones, were responsible for brain changes during critical periods in development which led to sexually dimorphic behaviors in adulthood, especially those related to sexual behavior, sexual preference, and rearing of young.  One could castrate a young male rat and that rat would fail to behave in the typical masculine fashion as an adult.  Similarly, one could inject a young female rat with testosterone, and that female rat would later mount other female rats as an adult.  Dissection of these rats showed that certain regions of their brains showed sexually dimorphic structures that were changed to be more like the opposite sex to the presence or lack of testosterone.  Since these behaviors are similar in nature to behaviors found in humans this led to the belief that these changes should be present in human brains as well,  and that humans should have sexually dimorphic brain structures as well.  In the beginning of the research into possible sexually dimorphic brain structures, it was thought that there were be only a few areas involved.  But, as techniques for brain research improved, it was found that more and more areas were involved.  Eventually, it became standard practice to consider each part of the brain sexually dimorphic until proven otherwise!

From the early work, it was recognized that some areas of the brain must be sexually dimorphic from early in embryonic development, while others only become sexually dimorphic later.  It has been found that some effects are ‘locked-in’ by exposure to sex hormones at different times in development.  There are associated behavioral consequences to these locked in changes.  These are referred to as “organizational effects” of the sex hormones.  Other effects were found to occur later, and even be reversible, for example, testosterone will increase both libido and aggressive behaviors, and even improve one’s spatial navigation and mental object rotation skills, while estrogen will increase verbal language skills.  But, stop taking these hormones, and the effects will reverse back to previous levels.  These kinds of effects are called “activation effects”.  Both of these kinds of effects involve changes in both relative size, morphology, and density of neural connections in different areas of the brain.  It turns out, that using cross-sex hormones, even in adulthood, really does make one’s brain look more like the other sex!

Much is made of the research on the sexually dimorphic brain differences between transsexuals and non-transsexuals by transsexuals who find comfort in them and believe that they “prove” that they in fact have the neurological organization of their preferred target sex (gender identity).  But what is this evidence and how significant is it?  Further, are these observed differences from early exposure to anomalous sex hormones (or differences in receptor density or sensitivity, which has the same effect) or are they the result of later, exogenous hormones, from Hormone Replacement Therapy (HRT)?

The most well-known study by Zhou, et. al.  involved a very small number of subjects.  The team specifically searched for areas of the brain that were sexually dimorphic but were not known to also be associated with sexual orientation.  This is potentially most of the brain!  They were specifically looking for an area of the brain which would provide a unitary theory of transsexuality, an area of the brain which would be effected in the same way in both HSTS and AGP transsexuals and thought that they had found it in the BSTc.  The study failed in two ways, first, they failed to include any HSTS subjects, mistakenly using self-reports of sexual orientation, they were all in fact AGP; second, the BSTc turns out to be sexually dimorphic only in adulthood.  That is to say, that this area is very plastic, responding to sex hormones, the sexually dimorphic structure being an “activation effect”, casting serious doubt on the value of the entire study.  Anne Lawrence has a very well thorough discussion of this study, which you may want to read:

http://www.annelawrence.com/brain-sex_critique.html

For more essays on trans-brains see Brain Sex.

 

Counting Noses…

Among those who acknowledge that there are indeed autogynephilic males who seek and obtain somatic feminization there is a common belief that they must be the odd man out, so to speak.  However, the data does not support this belief.  On the contrary, the data says quite the opposite.  Consider the 2005 Netherlands study, looking at self-report of sexual arousal to cross-dressing, by definition, an expression of autogynephilic arousal.  Those who report Erotic Cross Dressing are nearly half of the total population:

ECD  46  (45%)

Not  56  (55%)

However, if we look at those who self-report being presently gynephilic, we see that percentage climb significantly:

ECD  28  (64%)

Not  16  (36%)

Fully two thirds of those transsexuals who self-identify as gynephilic readily admit to being autogynephilic.  This is hardly a small handful!  In addition, Blanchard has shown that many transgendered males who state that they do not have sexual arousal to cross-dressing, none-the-less experience physiological arousal as measured by increases in penile volume when listening to narration of cross-dressing literature.  Thus, for a number of TS folk, the self-report of no arousal is likely unintentionally inaccurate, leading to smaller reported numbers.  If we also consider that acknowledging erotic cross-dressing is potentially shame provoking and that some individuals may also believe that such admissions may hurt one’s chances of receiving medical services, they may fail to report it. Further, this is only an assessment of erotic cross-dressing.  There are also TS folk who acknowledge other forms of autogynephilic arousal which do not include the use of cross-dressing.  Some report arousal to the thought of being or becoming female in an of itself.  They find the thought of being female, of having female anatomy, sexually arousing and may use such imagery as an aid to arousal during masturbation or even partnered sex.  If an individual uses autogynephilic ideation in which she is a nude female, use of cross-dressing is not going to useful, nor reported.  The Netherlands study did not capture this data, so we must count these percentages as a lower bound to the percentage of transsexuals who are autogynephilic.

Contrast this with Lawrence’s resorted Netherlands (Smith) exclusively androphilic group combined with the group from Leavitt and Burger (L&B) who also had no sexual experience with women:

Study:  Smith         L&B               Total

ECD   5 (15%)     1 (7%)         6   (12%)

Not  29 (85%)   14 (93%)   43  (88%)

Thus, when we look at those individuals who self-identify as androphilic and that they have not had sexual experience with women, we see a very different pattern.  Very few report erotic cross-dressing.  We know that there are individuals who originally self-identified as gynephilic before transition, but report that they are are self-identified as androphilic post-transition.  (How this happens is perhaps a subject for another post?)  We also know that there are transsexuals who self-identify as asexual, who Blanchard has shown have similar levels of self-reported autogynephilic arousal as those who self-identify as bisexual and gynephilic, so it isn’t a stretch to imagine that there would be a small number of TS folk who would be more like a cross between the asexual and bisexual group, having no experience with women, but still self-identifying as androphilic.  Indeed, we see that in Leavitt and Burger’s study, that there are those who self-identify as being androphilic but have never actually had sex with a man! This may explain the small number of self-identified autogynephilic “androphilic” transsexuals.

In addition to showing a significantly reduced number of individuals reporting erotic cross-dressing, exclusively androphilic transsexuals show a distinctly different clinical profile.  They have been obviously feminine from early childhood and begin living full time as women at a much younger age than those who are not exclusively androphilic.  In fact, the clinical presentation difference is so noticeable, as to lead us to conclude that they are a distinctly different population, with a different etiology.

If we take these differences between the two groups, and the similarities within each group, we can create a description of the “prototypical” member of each.  While no one individual will conform to the prototype in all respects, it still has clinical value to describe each.

The prototypical feminine androphilic transsexual was called a “sissy” by her peers growing up.  She avoided rough & tumble activities.  Her primary social circle consisted of one or two girls.  She actively participated in girls games and imaginary play.  Her parents were embarrassed by her femininity, and may or may not have sought professional help in trying to discourage her behavior.  As a young teen, she became interested in girls fashion and make-up, often exploring how she might look as a girl by dressing up and experimenting with make-up.  This did not involve erotic cross-dressing.  She had crushes on boys at school.  Her peers thought she might be homosexual.  She was hassled, perhaps even bullied, by homophobic boys, but otherwise was reasonably popular in her chosen circle.  She was considered very neat and well dressed in boy’s clothes.  She sought out opportunities to interact with small children and infants, taking on babysitting jobs.  As she approached adulthood, looking at her own nature, her potential future, both romantic and economic, made a rational decision to transition to living as a girl so as to grow up to be a woman socially.  Her family may or may not have disowned her in late adolescence.  As she is naturally feminine, she found that she was socially and romantically more successful as a woman.  She actively dated men while pre-op, but assiduously avoided direct contact with her penis, finding that emotionally uncomfortable.  She lived several years as a woman, taking feminizing hormones, before having SRS to improve her sex life, replacing genitalia that she didn’t use with those that she did.

The prototypical autogynephilic transsexual was accepted as a boy as a child, though she wasn’t the most masculine.  She was often a “loner”, finding her hobbies and reading to be more rewarding, but still willing and ready to participate in rough & tumble play.  She often envied girls and observed them more often than most masculine boys.  As she entered puberty, she began erotic cross-dressing in private, often masturbating while dressed, usually with lingerie.  She found this shameful and hid her cross-dressing as best she could.  She entertained thoughts of living as a woman, often in very idealized situations.  As a young adult, she dated women, often finding it necessary to imagine that she was female to “perform”.  She typically hid this fact from her dates.  She fell in love and found that the previously growing desire to live as a woman abated for a while.  She married and had children.  Her need to cross-dress… and use autogynephilic ideation grew, as the first blush of their romance matured into committed love.  She agonized about it obsessively, trying alternatively to push it out of her thoughts and trying to appease it by cross-dressing.  At one point, perhaps in her early 30s, or in her late 50s, a set-back or other significant personal change brought all of these feelings to the fore… and she made the fateful decision that she could no longer ignore her sexuality.  After having tried to ignore the cognitive dissonance between her successful social identity as a man, husband, and father, and her obligatory autogynephilic image of being female, concluded that the female image is her “true” image.  She then made steps to begin counseling with a gender therapist, obtained prescription for feminizing hormones, and then began the painful steps to living full time as a “transsexual”, since she had too many social connections who know of her previous status as a man.  She had SRS within a short time of nominally living as a woman, as she was impatient, feeling like she had waited long enough in her previous life as a man.  Her wife may or may not have demanded a divorce.

Again, although recognizing not every individual will fit the prototype (lest we fall into believing stereotypes), these profiles still describe a large number.  However, it should be noted that feminine androphilic transsexuals are much more likely to be like the prototypic description than autogynephilic type.  There is simply more variation in the autogynephilic population in their responses to their condition.  Having described the prototypical autogynephilic transsexual, we can see that even those who report, nay, insist, that they do not experience autogynephilic arousal, still closely fit the clinical profile.  We can, as makes sense in evidence based medicine, assume if an individual fits the clinical profile, then they belong to that class.  Indeed, common sense would demand, that if they “walk like a duck”…

Although difficult to sort out, I am interested in trying to calculate how many folk are likely feminine androphilic (homosexual) transsexuals (HSTS) and how many are non-exclusively androphilic, likely autogynephilic (AGP) transsexuals, as percentages.  If we make the assumption that Lawrence accidentally excluded the same number of feminine androphilic transsexuals as the number of AGPs she accidentally included, we can ignore the small number of self-reported AGP TS folk in her androphilic sample.  (I believe this is valid because human lives are messy.  One can imagine that under certain circumstances an MTF transkid may have been briefly married, and thus accidently excluded.  e.g. I personally know an MTF transkid who, because of parental expectations and community pressure, married her best friend, both were still virgins… that “marriage” lasted only long enough to find out that this had been a very bad idea, and ended with them jointly, happily, hiring a lawyer to process the paperwork.)  This would give us a rough estimate of the ratio:

Transkid    37  (33%)

AGP             75  (66%)

Thus, we find that the majority of transsexuals are autogynephilic, likely out-numbering the feminine androphilic transsexuals two to one.  However, if we assume that Lawrence did not accidentally exclude any transkid, then we must remove all of those that report erotic cross-dressing, as well as removing those that didn’t report either way just for good measure:

Transkid    29  (26%)

AGP             80  (74%)

Which would mean that AGPs out number MTF transkids by three to one.  It could even be higher, if several of those self-identifying as androphilic had failed to report their autogynephilic arousal.  If we assume that the number that reported is the same as those that didn’t report, that would move another five from the Trankid to the AGP catagory:

Transkids    24  (22%)

AGP                85  (78%)

Which is about four to one.  From personal experience, over the years, this number seems more realistic to me.  But in any case, we have numbers that range from 45% that absolutely admit to being AGP up to 80% that are likely to be.  Far from being rare, the autogynephilic transsexual is the majority, no matter how you slice it.

Addendum 4/2/2013:

The ratio of AGP vs. exclusively androphilic transwomen varies by culture, as Anne Lawrence has shown.  The Anglo-American culture has the highest ratio and more extended family (collectivist) cultures have the lowest.  See the this essay for more information.

References:

Male-to-female transsexual subtypes: Sexual arousal with cross-dressing and physical measurements
Lawrence, A.
http://akikos-planet.cocolog-nifty.com/blog/files/maletofemale_transsexual_subtypes_sexual_arousal_with_crossdressing_and_physical_measurements_319320.pdf

Transsexual subtypes: Clinical and theoretical significance
Yolanda L.S. Smith, Stephanie H.M. van Goozen, A.J. Kuiper, Peggy T. Cohen-Kettenis
http://akikos-planet.cocolog-nifty.com/blog/files/psychiatry_research__transsexual_subtypes_clinical_and_theoretical_significance.pdf

Clinical Patterns Among Male Transsexual Candidates with Erotic Interest in Males
Frank Leavitt, Ph.D., Jack C. Berger, M.D.
http://www.springerlink.com/content/fp15j71n57474k1l/