Dr. Leffert graduated from Brown University and the University of Minnesota Medical School. In 1983, he moved to Dallas to begin his internship and residency in Internal Medicine at the University of Texas (UT) Southwestern Medical Center. He was awarded the AHA Bugher Fellowship in Molecular Biology to begin his research fellowship at UT Southwestern, and then received a NIH Physician-Scientist Award in 1989 for his work in cloning the rat amylin cDNA. Dr. Leffert completed his clinical fellowship in 1991, also at UT Southwestern, and entered private practice in Dallas.
In 2007, Dr. Leffert formed North Texas Endocrine Center through a partnership with Dr. Peter Bressler, and currently serves as Managing Partner.
Dr. Leffert joined AACE in 1993 and became a fellow in 1995. He served as an Advisor to the Board in 2004 and 2005, and served two consecutive terms on the Board of Directors before his election to the Executive Committee as Secretary in 2013. As a result of his legislative interests, Dr. Leffert became Chair of the Legislative Committee, and has either been a member of or chaired most of the significant committees at AACE. Most recently, he chaired the Program Committee for the 2016 AACE Annual Scientific & Clinical Congress held in Orlando. Dr. Leffert is the AACE Delegate to the AMA House of Delegates, and will begin service on the ABIM Subspecialty Board of Endocrinology, Diabetes and Metabolism on July 1, 2016.