The complex hormonal changes that accompany the aging process, in particular the declining levels of estrogen as a woman approaches menopause, are thought to be the underlying cause of hot flashes. A disorder in thermoregulation (methods the body uses to control and regulate body temperature) is responsible for the heat sensation, but the exact way in which the changing hormone levels affect thermoregulation is not fully understood.

Hot flashes are considered to be a hallmark characteristic symptom of the menopausal transition. They also occur in men and in circumstances other than the perimenopause in women as a result of certain uncommon medical conditions that affect the process of thermoregulation. For example, the carcinoid syndromewhich results from a type of endocrine tumor that secretes large amounts of the hormone serotonin can cause hot flashes. Hot flashes can also develop as a side effect of some medications and sometimes occur with severe infections or cancers that may be associated with fevers and/or night sweats.