BIRTH ORDER AND ANDROPHILIC MALE-TO-FEMALE TRANSSEXUALISM IN BRAZIL.

Autor:	Vanderlaan DP; Department of Psychology,University of Toronto Mississauga,Mississauga,Ontario,Canada., Blanchard R; ‡Department of Psychiatry,University of Toronto,Toronto,Ontario,Canada., Zucker KJ; ‡Department of Psychiatry,University of Toronto,Toronto,Ontario,Canada., Massuda R; §Gender Identity Program-PROTIG,Hospital de Clinicas de Porto Alegre,Rio Grande do Sul,Porto Alegre,Brazil., Fontanari AMV; §Gender Identity Program-PROTIG,Hospital de Clinicas de Porto Alegre,Rio Grande do Sul,Porto Alegre,Brazil., Borba AO; §Gender Identity Program-PROTIG,Hospital de Clinicas de Porto Alegre,Rio Grande do Sul,Porto Alegre,Brazil., Costa AB; §Gender Identity Program-PROTIG,Hospital de Clinicas de Porto Alegre,Rio Grande do Sul,Porto Alegre,Brazil., Schneider MA; §Gender Identity Program-PROTIG,Hospital de Clinicas de Porto Alegre,Rio Grande do Sul,Porto Alegre,Brazil., Mueller A; §Gender Identity Program-PROTIG,Hospital de Clinicas de Porto Alegre,Rio Grande do Sul,Porto Alegre,Brazil., Soll BMB; §Gender Identity Program-PROTIG,Hospital de Clinicas de Porto Alegre,Rio Grande do Sul,Porto Alegre,Brazil., Schwarz K; §Gender Identity Program-PROTIG,Hospital de Clinicas de Porto Alegre,Rio Grande do Sul,Porto Alegre,Brazil., Da Silva DC; §Gender Identity Program-PROTIG,Hospital de Clinicas de Porto Alegre,Rio Grande do Sul,Porto Alegre,Brazil., Lobato MIR; §Gender Identity Program-PROTIG,Hospital de Clinicas de Porto Alegre,Rio Grande do Sul,Porto Alegre,Brazil.
Jazyk:	angličtina
Zdroj:	Journal of biosocial science [J Biosoc Sci] 2017 Jul; Vol. 49 (4), pp. 527-535. Date of Electronic Publication: 2016 Nov 07.
DOI:	10.1017/S0021932016000584
Abstrakt:	Previous research has indicated that biological older brothers increase the odds of androphilia in males. This finding has been termed the fraternal birth order effect. The maternal immune hypothesis suggests that this effect reflects the progressive immunization of some mothers to male-specific antigens involved in fetal male brain masculinization. Exposure to these antigens, as a result of carrying earlier-born sons, is hypothesized to produce maternal immune responses towards later-born sons, thus leading to female-typical neural development of brain regions underlying sexual orientation. Because this hypothesis posits mechanisms that have the potential to be active in any situation where a mother gestates repeated male fetuses, a key prediction is that the fraternal birth order effect should be observable in diverse populations. The present study assessed the association between sexual orientation and birth order in androphilic male-to-female transsexuals in Brazil, a previously unexamined population. Male-to-female transsexuals who reported attraction to males were recruited from a specialty gender identity service in southern Brazil (n=118) and a comparison group of gynephilic non-transsexual men (n=143) was recruited at the same hospital. Logistic regression showed that the transsexual group had significantly more older brothers and other siblings. These effects were independent of one another and consistent with previous studies of birth order and male sexual orientation. The presence of the fraternal birth order effect in the present sample provides further evidence of the ubiquity of this effect and, therefore, lends support to the maternal immune hypothesis as an explanation of androphilic sexual orientation in some male-to-female transsexuals.
Databáze:	MEDLINE
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