Good grief! My moons are gone, too. I remember having them years ago, but can't tell you when they disappeared. My nails were extremely brittle and prone to snags before starting thyroid meds, but that was one of the first things to change for me. As for actually splitting, all of my nails fractured straight across twice. Going by rate of growth, the nail beds were damaged when I was briefly on Pravachol and briefly on Lipitor. I only stayed on each one a few days, as I had severe muscle pains within 48 hours. As it turns out, my cholesterol numbers are coming down as I get my thyroid back in shape.