When we enter menopause our oestrogen, progesterone and testosterone all decrease (albeit at different rates), hot flashes have been linked to the decrease in oestrogen which usually occurs 2-5 years before your last period and continues to decrease afterwards. There is still no consensus on the definite cause of hot flashes, although the most probable theory is that because oestrogen acts like a magnet for glucose (energy) to the brain, when we go through menopause the energy the brain centre for temperature regulation (hypothalamus) has, has decreased and hot flashes ensue, particularly when there are other stressors involved.