There are serious doubts about the validity of the postulated metaplasia of Barrett's esophagus. The appearances can be better explained by esophageal shortening. What can be done about it. On the first question I have some clues. One of them is the dramatic postpartum relief of the heartburn, nausea and vomiting of pregnancy - not due to pressure of the gravid uterus on the diaphragm as is usually supposed.
Progesterone is surely the cause as it also produces pyrosis in patients on birth control pills.
There are also hormones of intestinal origin that could affect the LM, particularly CCK and secretin. Fats entering the duodenum trigger CCK secretion triggering smooth muscle contraction in the GB to inject emulsifying bile into the duodenum. Patients with pyrosis are often greatly improved by cholecystectomy. The connection warrants looking into. The gallbladder requires CCK to contract.