Hot flashes are due to the hypothalamic response to declining ovarian estrogen production.
Extremely high pulses of LH occur during the period of declining estrogen production. The LH has vasodilatory effects, which leads to flushing. For some women the loss is so great that they actually find sex repulsive, in much the same way as they felt before puberty. What hormones give, loss of hormones can take away. There is a feeling of loss of self.