Transsexual people experience a gender identity that is inconsistent with their assigned sex, and desire to permanently transition to the sex or gender with which they identify, usually seeking medical assistance (including sex reassignment therapies, such as hormone replacement therapy and sex reassignment surgery) to help them align their body with their identified sex or gender. Transgender people have a gender identity or gender expression that differs from their sex assigned at birth. Some transgender people who desire medical assistance to transition from one sex to another identify as transsexual. Transgender, often shortened as trans, is also an umbrella term. In addition to including people whose gender identity is the opposite of their assigned sex (trans men.). transgender evidence on the biological nature of gender identity date february 13, 2015 source boston university medical center summary medical care of. A worker checks the serial number on a slice of human brain before using a saw to cut a piece from the sample at a brain bank in the bronx borough of new york city, new york, u. transgender research the role of biology in gender identity development written by kristin della volpe recent studies provide evidence that biology plays a role in transgender identity development, explained stephen m.