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GSI Doctors

Our Physicians are all Board Certified

Board certification means that doctors have completed the amount of training that a specialty board requires. These physicians have practiced for a specified period of time and passed rigorous written and oral exams. Board certification is generally accepted as a strong indicator of a physician’s competence and experience.

Dr. Hood John R. Hood, MD
Dr. Hood received his B.S. from Oral Roberts University in Tulsa, Oklahoma. He went on to earn his M.D. at the University of Oklahoma in Oklahoma City, Oklahoma, June 1982. Following medical school, he completed his residency and fellowship in Oklahoma City, at the University of Oklahoma Medical College, 1987 and the Oklahoma City Teaching Hospital in 1989. Dr. Hood is board certified in Internal Medicine and Gastroenterology by the American Board of Internal Medicine (ABIM).
  • H.S. - Robert H. Goddard H.S. , Roswell, NM 1971
  • College - Oral Roberts University , Tulsa, OK 1976
  • Med School - University of Oklahoma , Oklahoma City, OK 1982
  • Board Certified Internal Medicine and Gastroenterology
  • Fellow of American College of Gastroenterology
  • Core Belief: All healing comes from God.


Dr. Martin Michael J. Martin, MD
Dr. Martin has special interests in the diagnosis and management of a wide array of gastrointestinal disorders and colon cancer prevention. He was awarded honours at the University of Texas and later went on to graduate from the University of Texas Medical School at San Antonio. He completed his Internal Medicine Residency at the University of Oklahoma, College of Medicine, Tulsa, and his Gastroenterology Fellowship at the University of Texas Health Sciences Center, M.D. Anderson and affiliated hospitals in Houston, Texas. He and his wife loved northeast Oklahoma, so they and their family returned here to live in 1994. He has served as Chief of Gastroenterology and Endoscopy at St. Francis Hospital and has been involved with teaching residents. He loves "doing life" with all kinds of people and has travelled to other countries for medical missionary work. He enjoys spending time with his family and is active with various volunteer endeavours in the community and church. Dr. Martin has been certified by the American Board of internal Medicine and Gastroenterology.

Dr. Briggs William K. Briggs, MD
Dr. Briggs received his B.S. from the University of Oklahoma in Norman, Ok. He went on to earn his M.D. at University of Oklahoma in Tulsa, Oklahoma. Following medical school, he completed his residency at University of Oklahoma College of Medicine in Tulsa, Oklahoma and his fellowship in New Orleans, Louisiana at Louisiana State University. Dr. Briggs is board certified in Internal Medicine and Gastroenterology by the American Board of Internal Medicine (ABIM).


Dr. Bigler Jeffrey L. Bigler, MD
Dr. Bigler received his B.S. from the Southwest Baptist University in Bolivar, Missouri. He went on to earn his M.D. at University of Oklahoma in Tulsa, Oklahoma. Following medical school, he completed his residency at University of Oklahoma and his fellowship at University of Missouri in Columbia, Mo. Dr. Bigler is board certified in Internal Medicine and Gastroenterology by the American Board of Internal Medicine (ABIM). Interested in psychological aspects of some GI disorders. I decided to be a gastroenterologist after my father was diagnosed with colon cancer while I was in Medical School Member of AGA, ASGE and ACG. Married to Jennifer with 6 children, one girl and five boys. Primary interests: Inflammatory Bowel Disease, Colon Cancer Screening, IBS, Functional Abdominal Pain.
  • Primary Interests: Inflammatory Bowel Disease, Colon Cancer screen, IBS, Functional Abdominal pain
  • Married to Jennifer with 6 children (one girl, and 5 boys)
  • Member of AGA, ASGE & ACG
  • Interested in psychological aspects of some GI disorders


Dr. Berger Sheldon C. Berger, DO
Dr. Berger received his B.S. from the University of Kansas in Lawrence, Kansas. He went on to earn his D.O. at University of Health Sciences College of Osteopathic Medicine in Kansas City, Missouri. Following medical school, he completed his residency at Tulsa Regional Medical Center and his fellowship at the Chicago Osteopathic Hospital System, Chicago, Illinois. Dr. Berger is board certified in Internal Medicine and Gastroenterology by the American Osteopathic Board of Internal Medicine.
  • Undergraduate education at University of Kansas
  • Medical school in Kansas City, MO. with internship & residency in Tulsa, OK.
  • Gastroenterology fellowship in Chicago, IL.
  • Board certified in Gastroenterology
  • Tulsa resident for greater than 20 years


Dr. Morris David W. Morris, DO
Dr. Morris received his B.S. from the Oklahoma State University in Stillwater, Oklahoma. He went on to earn his D.O. at College of Osteopathic Medicine, Oklahoma State University in Stillwater, Oklahoma. Following medical school, he completed his residency at Tulsa Regional Medical Center and fellowship in Olympia Fields, Illinois at the Chicago College of Osteopathic Medicine. Dr. Morris is board certified in Internal Medicine and Gastroenterology by the American Osteopathic Board of Internal Medicine.
  • Graduate of Oklahoma State University and Oklahoma State University College of Osteopathic Medicine
  • Active in international and local mission work
  • Active in multidisciplinary clinical medical research since 1994
  • Board certified in Gastroenterology and Internal Medicine
  • Fellow American College of Osteopathic Internists


Dr. Thompson Roy L. Thomspon, MD
Dr. Thompson graduated from Broken Arrow High School. After graduating from Oklahoma University with a degree in biochemistry, he also obtained his medical degree from OU. He then trained at the University of Tennessee in Memphis for his residency, chief residency and fellowship in gastroenterology. He maintains board certifications in internal medicine and gastroenterology. Away from work he enjoys spending time with his family, friends and church family.


Dr. Fillmore Geoffrey A. Fillmore, DO
Dr. Fillmore received his B.S. from the University of Central Oklahoma in Edmond, Oklahoma. He went on to earn his D.O. at University of Osteopathic Medicine in Tulsa, Oklahoma. Following medical school, he completed his residency and fellowship in Temple, TX, at Scott and White Memorial Hospital. Dr. Fillmore is board certified in Internal Medicine and Gastroenterology by the American Board of Internal Medicine. Dr. Fillmore has also received additional extensive training in endoscopic ultrasound (EUS) and performs these procedures at our contracted hospitals.
  • Oklahoma State University College of Osteopathic Medicine, Graduated 2004
  • Residency: Internal Medicine Scott & White Hospital, Temple, TX 2004 - 2007
  • Internal Medicine Chief Resident 2007 - 2008
  • Gastroenterology Fellowship Scott & White Hospital 2008 - 2011
  • Certified American Board of Internal Medicine and Gastroenterology
  • Interests in general gastroenterology and endoscopic ultrasound

Contact Us

Yale Location
6565 S. Yale #1200
Tulsa, OK 74136
(918) 494-9433

Garnett Location
Berkshire Plaza
1621 S. Eucalyptus Ste 102
Broken Arrow OK, 74012
(918) 806-5222
Fax: (918) 494-9499

This should not be used in case of an emergency. If you are having an emergency, please call the clinic or emergency personnel (911) directly.

If you are a patient, please contact us through the Patient Portal. If you are NOT a patient, please call us at 918.494.9433 or 918.806.5222.

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