Hi Ellen!

What happens is that Estrogen is often stored in fat and when the fat is released, so is the extra Estrogen. That can cause a whole array of symptoms from extra PMS symptoms to earlier or more frequent periods. Yes, it does settle down as weight loss slows and your body adjusts. Many women actually report that their PMS symptoms are much less severe while following low carb.
From my own experience, I always experience breast tenderness as soon as I ovulate and it doesn't go away until my period begins. Funny enough, that was how I knew I was pregnant (after the first time)...the tenderness was always worse when I was pregnant.