Gut and Thyroid, Chicken and egg

Which comes first, the thyroid issues causing gut issues, or gut issues and leaky gut causing inflammation which suppresses the thyroid? What if I told you, they not only feed each other, but the initial root would change depending on certain scenarios within each case? I have seen both sides of the coin, and once the root is fixed, they all fix, but if not, they worsen each other drastically.