The development of Nipples isn't influenced by hormones, only the functionality and the growth of glands and tissues behind them. For an example of development influenced by hormones, look at the genitalia, they only form when certain hormones are present, and in certain individuals, androgens are ignored or partially ignored during development, and a middle ground between a snake and a vagina is formed with a strange combination of testes and a shallow vagina. How odd!
You're gender is decided when sperm hits egg.
Alas, no, many defining aspects of gender are there because of hormones. If certain hormones aren't, or are present when they shouldn't be in such quantities, then you can get females growing facial hair and men growing breasts and other strange phenomena normally restricted to circuses.
