What college are you going too? The brain is charge with producing some hormones but NOT the sex hormones, these are produced by the testicles or ovaries, testosterone is produced in the testicles and oestrogen is produced in the ovaries.
Anyway it is agreed by most people it is caused by early development in the womb, it is theorised that hormonal influences in the womb cause the brain to develop so it believes it is the opposite gender from what the body is. Although he male and female mind are more or less the same certain areas of the brain are more active in males than in females and vice versa. Basically in a trans person, the wrong zones producing greater activity which basically causes the brains confusion, cos in essence it is thinking as if it were the opposite gender.
Another thing that possibly influences the development of a transsexual person is it was discovered in trans people the androgen regulator gene, the gene charge with converting oestrogen to testosterone in women and testosterone to oestrogen in males to give that balance of both hormones is slightly longer than it should be, chemistry 101, greater surface area for a reaction the faster it will take place meaning more oestrogen is being produced than should be in someone born male and vice versa in someone born female who is trans.
20 year old pre-op male-to-female transsexual