Many factors are directly involved in BA malabsorption in CF such as (see Figure 1): defective CFTR channels [17], small intestine bacterial overgrowth (SIBO) [9], increased BA losses, decreased BA resorption in the terminal ileum, and an impaired BA interaction with the hepatic and intestinal farnesoid X receptor (FXR), which modulates cholesterol 7α-hydroxylase (CYP7A1), the rate-limiting enzyme in BA synthesis [5,18,19]. The gene discussed is CYP7A1; the disease is cystic fibrosis.