Scientists have discovered that breast cancer can disturb the brain’s daily stress hormone rhythms early in disease development.
“The brain is an exquisite sensor of what’s going on in your body,” says Cold Spring Harbor Laboratory Assistant Professor Jeremy Borniger. “But it requires balance. Neurons need to be active or inactive at the right times. If that rhythm goes out of sync even a little bit, it can change the function of the entire brain.”
Researchers in Borniger’s lab have shown that breast cancer alters the normal daily pattern of stress hormone release in mice. The hormone involved is corticosterone, which plays a central role in the rodent stress response. In people, the comparable hormone is cortisol.
Under healthy conditions, these hormones follow a predictable cycle, rising and falling over the course of the day. In mice with breast cancer, however, the researchers found that tumors dampen this natural pattern, leading to a flattened hormone profile that is associated with poorer quality of life and higher rates of death.
Stress, Sleep, and the Body’s Internal Clock
When daily biological rhythms are disturbed, the effects can extend well beyond hormone levels. In humans, disrupted rhythms have been linked to stress-related problems such as insomnia and anxiety, both of which are frequently reported by people with cancer.
Maintaining stable stress hormone levels depends on a tightly regulated feedback system known as the HPA axis. This system connects the hypothalamus (H), pituitary gland (P), and adrenal glands (A), which constantly communicate to keep the body’s internal timing on track and preserve regular daily rhythms.
