Female mice that had never become pregnant had approximately 15 times as much cancer in their bladders as their counterparts that had become pregnant, according to new findings.
The researchers focused on the open question: Why does bladder cancer affect about three times as many men as women? Scientists long blamed men's historically higher rates of smoking and greater exposure to dangers in the workplace, but the gap has persisted even as women swelled the workforce and took up smoking in greater numbers.
The authors of the study investigated ways in which hormones might make males more vulnerable to bladder cancer. They compared rates of bladder cancer in male and female mice and, taking a closer look at the female ones, found a marked difference in cancer rates and volumes among those.
Female mice that had gotten pregnant repeatedly had far fewer bladder cancers than both their normal male counterparts and their female counterparts that had never gotten pregnant. On average, the total tumor volume was about 15 times greater in female mice that had never gotten pregnant compared to mice that had gotten pregnant.
The mice that were pregnant nursed their offspring and a protective effect could be related to pregnancy, lactation or both, the scientists suggest. The results highlight a possible role for hormones in bladder cancer, perhaps like the known role hormones have in the development of breast cancer.
In a study of April, the same team dealt with the way male hormones might boost bladder cancer risk. They demonstrated a link between testosterone and the ability of new tissue to form new blood vessels, a crucial ability for cancerous tissue as it seeks to grow.
MEDICA.de; Source: University of Rochester