freemartin syndrome

…to male hormones results in freemartin syndrome, in which the female is masculinized; this commonly is seen in cattle and rarely in humans. In human blood chimeras of the same sex, chimerism may be detected through routine blood typing, when unexpected results prompt further genetic investigation.

Lillie also demonstrated that bovine “freemartinism” is a classic example of hormonal intersexuality in which a male fetus influences the development of its female twin. Cattle twins may consist of two males, two females, or a male and a “freemartin,” an apparent female possessing a male’s internal reproductive system. Knowing…