What would happen if a girl suddenly started producing testosterone? and is it possible to happen?

Depends: Hi. Relatively mild over production of testosterone, as with PCOS generally causes hirsutism, oligomenorrhea/amenorrhea, and acne. More severe androgen exposure causes virilization with amenorrhea, hirsutism, and acne, but also voice deepening and clitoromegaly. The main source of testosterone in women are the ovaries. However, the adrenals can produce a very similar clinical picture.