There are gender differences in the odor of human urine, according to Nature World News. The hormone estratetraenol is only in female urine, and its scent produces a different reaction in straight men versus straight women or gay men.
Estratetraenol is a steroid hormone that researchers suspect may be a human pheromone, states Scientific American. It has no discernible odor of its own, but experiments have shown that the human nose can perceive it.
Only in female urine contains estratetraenol. A similar compound, androstadienone, is a male hormone, but can also be present in women's secretions, explains Scientific American.
A study involving human perception of both compounds found that straight men perceived a gender-neutral walking animation as more feminine after sniffing estratetraenol, Scientific American reports. Straight women and gay perceived the same animation as more masculine after sniffing androstadienone. Gay and bisexual women had no particular reaction to either compound.