There are 0 male hormones in the body from the start.
As an FYI, if that were true, it would be extremely unhealthy. Humans of all sexes* need proper levels of testosterone, estrogen, and other hormones to be healthy. Women generally have around 10-20% of the amount of testosterone that males have (
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) and, similarly, men need to have "female" hormones, like estradoil and esterone, in order to function properly (
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).
Furthermore, the evidence we have today shows that changes in hormone levels in adults seems to have little or no effect on sexual preference, and that any influence they have is only during childhood development (
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So, in the real world, if a male's brain remained the same, it being put into a female body wouldn't likely affect its sexual preferences.
That said, it's fiction, so it's all up to the author's discretion.
*: Yes, sex isn't simply binary male/female. It's often those two, but
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.