Abstract: The invention is in the field of disorders of glucose homeostasis therapy. In particular the invention relates to a CFTR inhibitor or an inhibitor of CFTR gene expression for use in the treatment of disorders of glucose homeostasis. The present invention also relates to an in vitro methods for increasing the pool of Ngn3+ endocrine progenitor cells, pancreatic endocrine cells, or ? cell mass obtained from stem cells, wherein said methods comprises the step of contacting stem cells with a CFTR inhibitor or an inhibitor of CFTR gene expression. The present invention also relates to a method of testing a subject thought to have or be predisposed to having disorders of glucose homeostasis, which comprises the step of analyzing a sample of interest from said subject for: (i) detecting the presence of a mutation in the CFTR gene and/or its associated promoter, and/or (ii) analyzing the expression of the CFTR gene.