Hot flashes and night sweats are signs of instability of the sympathetic nervous system. They typically appear as a feeling of intense heat lasting from two minutes to half an hour. Hot flashes may occur infrequently or several times a day and usually begin before menopause and may continue for years after menstruation has stopped. Menopause refers to the permanent cessation of menstruation, a process that can be natural, premature, or the result of surgery, radiation, or chemotherapy. In many women, this transition can affect many systems in the body, be accompanied by unpleasant symptoms such as hot flashes while increasing the risk of osteoporosis and cardiovascular diseases as estrogen levels decrease.