A person with deficient levels of testosterone or estrogen can increase his or her risk of suffering a torn rotator cuff, researchers say. A study examined the likeliness of these shoulder injuries to muscles and tendons surrounding the joint that hold the head of the upper arm bone into the shoulder socket. It found that women with low levels of estrogen had a 48% greater chance of rotator cuff injuries compared to women with normal estrogen levels. Men with low levels of testosterone had a 89% greater likelihood.