Positive correlation of body weight with pituitary tumor incidence in rats.

Data based on 4700 Wistar rats in 13 two-year studies were used to calculate the correlation between body weight at 12 months and pituitary tumor incidence. The positive correlations of 0.754 for male rats and 0.828 for female rats were both highly significant (p less than 0.0001). The results indicate that any treatment which causes increased body weight will probably be associated with an increased incidence of pituitary tumors.