do the darker nipples caused by hormones ever go away and they lighten up again?

I do believe they will lighten with time. I recall that during both of my pregnancies, my nipples went very dark but they lightened to their normal pink colour after breastfeeding for a while. I think it is the sky high hormone levels during pregnancy that causes the darkening and it should be the same for anyone getting darker nipples because of hormone intake. Once you stop, or lower the dose, the nips will get lighter.