Fish gonads are typically pairs of either ovaries or testes. Fish reproductive organs include testes and ovaries. Genetic sex determines whether the gonads will be testes or ovaries. These organs include the pituitary, thyroid, adrenals, ovaries, testes, and pancreas. The most common type of testicular cancer occurring in undescended testes is seminoma. Thus, many tissues producing steroids, including the adrenal glands, testes, and ovaries, produce progestogens. Symptom onset often follows physical activity or trauma to the testes or scrotum. It may also affect the ovaries in women and the testes in men. MIH and androgens cooperate to allow for movement of testes into the scrotum. It is often associated with the testes and ovaries. In turbellarians there are one or more pairs of both testes and ovaries. Cryptorchidism is the absence of one or both testes from the scrotum. After the individual mates, the weight and size of the testes and scrotum decrease. At least one contributing mechanism for reduced spermatogenesis in cryptorchid testes is temperature. LH acts on Leydig cells in the male testes and theca cells in the female.