Identical Reared apart Twins Concordant for Transsexuality – Review

This is a brief article about a case of identical twins reared apart who both had gender dysphoria. Unfortunately, it is based on an interview with only one of the twins. This makes it a suggestive report, but not scientific proof.

In addition, one of the twins was born with an intersex condition. This raises the question of whether his gender dysphoria was caused by genes or the prenatal environment.

The twins were born male and separated at birth and raised in different families. They did not meet each other until they were 15. DNA testing confirmed that they were identical twins.

This is only one case, so the conclusions we can draw are limited.

The main weakness of the report, however, is that it is based on the memories of only one of the twins, LT. The authors were able to interview LT in his 50s.* It is possible that his memories of meeting his twin AT 35 years ago would be incorrect or might exaggerate similarities or differences.

According to LT,

“Prior to meeting, by age 8 years both twins experienced gender discomfort, engaged in cross-dressing, and felt that they should have been born as the other gender. Also prior to meeting, both twins experienced unease with the anticipated and actual secondary sexual development of puberty. Furthermore, unbeknownst to his twin, at age 14 years LT was fully committed to undergoing sex reassignment surgery and so convinced his mother that she took him to see a urologist.”

According to the author of the report, this means that both twins met the criteria for gender dysphoria, “persistent cross-gender identification and a strong desire to change the sexual characteristics to those of the other gender.”

I am not comfortable with diagnosing someone you have not interviewed. Clearly, AT had some issues with his gender, but how did he define himself? Did he want to have surgery? Did the twins continue to have contact and did AT’s gender dysphoria persist into adulthood? Did they influence each other after age 15?

This report is also about a tragedy. AT committed suicide at age 35.

The twin’s birth mother had skin cancer and doctors believed she should give one twin up for adoption. AT was therefore put in a state-run institution and then adopted by a less well-to-do family. His parents were “religious, punitive, and rejecting of his cross-gendered behaviors.” (Presumably we know all this from his twin, LT.)

LT was raised by his biological parents. His family was more financially comfortable. His mother and sisters “supported his female identity as it developed and afterward.”

The authors of the study stress the importance of family support in preventing suicide, but there are a number of other factors that might have also influenced AT. Adoptees are more likely to attempt suicide than non-adoptees. It might also be upsetting to learn that you had a twin and your birth parents had kept them, as AT did. Having parents with a lower socio-economic status also increases the risk of suicide. AT was therefore more at risk for suicide to start with, although we also know that family support reduces the risk of suicide for people with gender dysphoria.

An interesting aspect of this study is that LT was a “sickly infant” and had hypospadias, a birth defect in the urethra. The Intersex Society of America lists it as an intersex condition. There is no information in the study as to whether or not AT also had hypospadias or any other intersex condition.

Did the hypospadias contribute to LT’s gender dysphoria? Could having a scar on your penis influence feelings about gender identity?

Could the hypospadias be a sign of something else that also caused LT’s gender dysphoria?

According to Wikipedia, the cause of most cases of hypospadias is unknown, but it may be influenced by: having an older mother, the mother taking progesterone during pregnancy, the fetus not producing enough testosterone or nor responding to it, or genetics. It seems reasonable to ask if these factors might also affect gender identity.

In this case, the mother was 40 when the twins were born, which might have been a factor in LT’s hypospadias. We don’t know about any hormonal factors.

We have no way of knowing what caused LT’s hypospadias, but it does raise the question of whether the twins’ issues with gender were caused by a genetic factor or something to do with the prenatal environment or the genital surgery.

I am frustrated by this study. It seems like a good case for a genetic component to gender dysphoria – twins reared apart are a classic test of genetic effects. Unfortunately, since it is based on the account of one twin, the evidence is not as strong. It might be that the twin who lived developed a narrative to make sense of his twin’s tragic suicide.

In addition, the fact that one twin had an intersex condition at birth might be a sign of something unusual in the twin’s prenatal environment.

Mostly, though, you can’t say you have scientific proof that the twins were alike if you only interview one of the pair of twins.

It is so very hard to get good data on gender dysphoria. People with gender dysphoria are extremely rare and twins with gender dsyphoria are even rarer. Add in a much-too-high suicide rate, and you have even less ability to collect data.

Once again, we need more research in this area. As Heylens et. al said in their review of the literature: “detailed registers of GID twins, preferably on MZ twins discordant for GID and DZ twins are needed, to gain more decisive information about the influence of genetic vs. environmental factors in the development of GID.

Original Case Report:

Identical Reared apart Twins Concordant for Transsexuality by Nancy Segal & Milton Diamond, Letter to the Editor, published in: Journal of Clinical and Experimental Medicine, April 2014 Volume 6, Issue 2, Page 74.

*The article refers to the twins with male pronouns. The article does not make it clear what the twins did when they grew up. LT, if you have transitioned and I am using the wrong pronouns, I apologize.

More about twins and gender dysphoria:

My review of “Gender Identity Disorder in Twins: A Review of the Case Report Literature.”