The researchers studied how removing ovaries, adrenal glands, or pituitary glands affected the growth of spontaneous tumors in mice. They found that removing adrenal glands or pituitary glands caused some tumors to shrink, but also led to shorter survival times for the mice. Adrenal gland removal alone or with ovary removal caused complete tumor regression in a small percentage of mice, while pituitary gland removal led to regression in a higher percentage of mice.