They are two faces of the same coin, basically your brain trying to make sure it has the glucose it needs to keep running. Because the brain runs entirely on glucose it will send signals to the body to keep glucose levels available for it come heck or high water. The brain does not care about
high blood sugar, it only cares about
its needs. The following is a very simplified unscientific explanation.
The Dawn Phenomenon is part of the body's rhythm of preparing us for the energy needed to rise and begin the day's activities until we can find food. (Think cave person needing to go out hunting and gathering.) In a normal it tells the liver and muscles to convert glycogen to glucose and put it out there before the morning to get us up and going. In Type2 diabetics the cells don't take up all the glucose they need to get going (insulin resistance) and it just floats around in the blood stream as a high reading amount. To compound the problem the liver may be putting out too much because of information it's getting from the cells that didn't get their glucose ration. Metformin is a medication that helps the insulin get into the cells so they get their ration. For this reason you may ask your doctor if you should be splitting your metformin dose between morning and nighttime so you have it available when your blood glucose starts to go high.
The Simogyi effect is often seen when a person exercises too much or doesn't eat their night time snack. If the glucose levels drop because there is no food available in the intestines to extract glucose from, or the muscles have used all the available glucose in exercise, the brain panics and sends out an alarm to the liver to convert some glycogen to glucose and pump some into the body pronto! The liver reacts and puts lots of glucose out into the blood stream and the brain is happy... but then the blood sugar is too high because we are asleep or have stopped exercising and we're not using the sugar. This is a rebound effect from sugar lows and can be treated with nightime insulin (I use Lantus.) as well as a small snack at bedtime or before exercise to keep the blood sugars level.
The real explanation for this can be found at: Hyperglycemia from the Dawn & Simogyi Effects
The total package of understanding Diabetes2 is to figure out how to keep the blood sugars in the low range and level thru most of the day and night. Our bodies want to take all of the food we eat and convert it to fat, making us more hungry so it can make more fat. Our anti-famine mechanism has gone haywire. The secret to successful blood sugar treatment for most of us is to make the foods we eat the kind that are mechanically slowly digested so there is a 'time release' effect of carbs entering the blood stream. This can be accomplished by eating more vegetables whose cell walls slow down digestion and avoiding easily absorbed carbs and sugars like pastas, white rice and desserts. Hope this helped.
~ Jeannie "People are like stained glass windows: They sparkle and shine when the sun's out, but when the darkness sets in
, their true beauty is revealed only if there is light within."- Elizabeth Kubler-Ross