Michelle Pietzak, M.D.


Michelle Pietzak, M.D.

Global TA Section Head, Gastroenterology

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Michelle is a board-certified gastroenterologist and pediatrician, with over 27 years of experience in treating complex intestinal, nutritional, liver and pancreatic diseases in both children and adults. She has almost 20 years of involvement with both global and local pharmaceutical companies and laboratories, contributing to drug design, clinical study development, data monitoring safety, FDA submissions and clinical/research laboratory regulation.

Work experience

Michelle joined Parexel in 2020 and brings medical leadership and expertise in gastroenterological, nutritional, hepatic and pancreatic diseases to clinical studies. Her main areas of expertise include pediatric nutrition, celiac disease, inflammatory bowel disease, non-alcoholic fatty liver disease, the intestinal microbiome and malabsorption.

Michelle served as an attending at the renowned Children’s Hospital Los Angeles (CHLA), At CHLA and USC, she successfully led many clinical areas, including as Chief of Pediatric Gastroenterology and Nutrition at USC, Co-Chair of the USC Keck School of Medicine GI-Liver System Core, Director of CHLA Nutrition Support Team and Chair of the CHLA Nutrition Advisory Committee. As GI representative for the CHLA Pharmacology and Therapeutics Committee and The Pharmacy Functional Project Team, she was successful in obtaining institutional approval for new drugs and devised and initiated pediatric patient databases for use in clinical research projects in the Division of Gastroenterology and Nutrition and CHLA.

Her past experiences in pancreatic diseases include collaborations with the Cystic Fibrosis Center at Children’s Hospital Los Angeles. Michelle also has experience in treating other conditions with exocrine pancreatic insufficiency, such as congenital malformations of the pancreas, Shwachman-Diamond syndrome, Johanson-Blizzard syndrome, chronic pancreatitis, acute necrotizing pancreatitis, hereditary pancreatitis (PRSS1, SPINK), celiac disease, Crohn disease, and Zollinger-Ellison syndrome.


Michelle received her M.D. at the State University of New York at Buffalo School of Medicine and Biomedical Sciences. She completed her residency in pediatrics and fellowship in gastroenterology and nutrition at Children’s Hospital Los Angeles and the University of Southern California Keck School of Medicine (USC).