Diabetes Team

Our Team - Geckle Diabetes & Nutrition Center at GBMC

James Mersey, MDJames Mersey, MD
Chief, Division of Endocrinology
Medical Director, Geckle Diabetes and Nutrition Center


Dr. Mersey received his undergraduate degree from Amherst College in Massachusetts and his medical degree from the Johns Hopkins School of Medicine in Baltimore, Maryland. He completed his internship and medical residency in Internal Medicine at Johns Hopkins Hospital and an endocrine fellowship in Endocrinology and Metabolism at Peter Brent Brigham Hospital, a division of Harvard Medical School, in Boston, Massachusetts. Dr. Mersey then spent 11 years on the full-time faculty at the University of Maryland in Baltimore and is now in private practice. He and his associate endocrinologists are actively involved in clinical research in diabetes, hypertension, lipid disorders and osteoporosis. Dr. Mersey is also the Chief of Endocrinology at Greater Baltimore Medical Center and Medical Director of the Geckle Diabetes and Nutrition Center at GBMC. He is an instructor for the GBMC medical residency staff and fellows and also retains faculty appointments at the University of Maryland School of Medicine and Johns Hopkins School of Medicine. Dr. Mersey is board-certified in both Internal Medicine and Endocrinology and is a fellow of the American College of Physicians and the American College of Endocrinology.

Karen M. Bolderman, RD, LDN, CDEKaren M. Bolderman, RD, LDN, CDE
Clinical Program Manager


Karen M. Bolderman, RD, LDN, CDE is the Clinical Program Manager of the Geckle Diabetes and Nutrition Center. She earned her Bachelor of Science degree in Human Ecology/Dietetics from Marywood University in Scranton, Pennsylvania and completed additional graduate studies in nutrition. She has more than 30 years of experience in the field of diabetes, having worked as a diabetes educator and research study coordinator for a large Baltimore endocrinology practice as well as served as a chief clinical and administrative director dietitian in several Baltimore and New Jersey hospitals. She also worked in the diabetes industry, and held clinical management positions with several insulin pump companies and was a diabetes-focused medical science liaison and medical information senior specialist for a diabetes biomedical company. She has been an active diabetes volunteer and officer on local, state, regional, and national levels of several diabetes professional organizations, including the national Board of Directors of the American Diabetes Association. She is a recipient of the Maryland Dietetic Association's Maryland Recognized Dietitian of the Year award and is a member of the American Academy of Nutrition and Dietetics' Diabetes Care and Education Practice Group and AADE Insulin Pump Specialty Practice Group. Ms. Bolderman has written various diabetes- and nutrition-related publications for both healthcare professionals and patients and has presented extensively to both healthcare professional and lay audiences on various diabetes- and nutrition-related topics.

Estelle Carter, BS, PA-C, CDEEstelle Carter, BS, PA-C, CDE
Certified Diabetes Educator


Ms. Carter is a Clinical Educator at GBMC's Geckle Diabetes Center. Her responsibilities include patient management, clinical instruction, pump training and program development. Ms. Carter is a physician assistant with over 30 years experience. In NYC she was employed at Beth Israel Medical Center, Montefiore Hospital and Kings County/Downstate Medical Center. She has been employed in Maryland as a Physician Assistant at Maryland General Hospital, University of Maryland and GBMC.

She has over 20 years experience as a certified diabetes educator working in NYC as well as here in Maryland She is a graduate of Long Island University's Physician Assistant Program in Brooklyn, New York. Ms. Carter's commitment to diabetes education is fueled by her passion to assist patients with diabetes self-management education in an effort to aid them with a healthier lifestyle and preventing or delaying complications. Her quest is to educate patients, families, medical personnel or anyone interested in learning about diabetes and its co-morbidities.


Rebecca Denison, RD, LD, CDE, Doctor of Integrated MedicineRebecca Denison, RD, LD, CDE, Doctor of Integrated Medicine
Certified Diabetes Dietitian Educator


Ms. Denison has been a Registered Dietitian for over 20 years and a Certified Diabetes Educator for almost 5 years. She is also a certified insulin pump trainer for the Animas Ping Pump and working toward her certification for the Minimed Pump and the Omnipod. She earned her Certificate of Training in Childhood and Adolescent weight Management in November of 2007. She provides professional and personal guidance and education to groups and individuals as they maneuver the intricacies of manipulating and improving their nutritional intake and changing their lifestyles to achieve the results they and their health care team desire. She empowers those she counsels to make decisions that blend with their own current life philosophy and abilities. She sees clients as young as 2 years of age to adulthood with a wide variety of diagnoses. Though the majority of her patients are diagnosed with Type 1 diabetes, Type 2 diabetes and Gestational Diabetes, she often sees patients with issues such as cholesterol (or lipid) management, failure to thrive, obesity, celiac disease and tube fed patients. The patients she sees often have multiple diagnoses and are not limited to only the above diagnoses. She enjoys a challenge and expanding her knowledge. However, if the patient is above her skill level, she will refer them to someone more appropriate for the patient's condition.  Her education includes a bachelor's degree in both nutrition and biology at Stephen F. Austin State University in Nacogdoches, Texas; a master's degree in nutrition at University of Texas in Austin and a doctoral degree in Integrative Medicine at Capitol University of Integrative Medicine in Washington, DC. Ms. Denison goes out in the community for diabetes screening at health fairs, supermarket tours, cooking classes and support groups in addition to seeing patients in the outpatient center at GBMC.

Joanne Dielmann, RD, LD ,CDEJoanne Dielmann, RD, LD ,CDE
Certified Diabetes Dietitian Educator


Ms. Dielmann graduated from the University of Delaware with a B.S in Nutrition and dietetics and completed a co-coordinated Master's Degree /Dietetic Internship program at the University of Alabama in Birmingham. She has spent the majority of her 25-year career span primarily working in outpatient and community nutrition. Before joining GBMC in 2003 she worked as an outpatient dietitian for many years at Franklin Square Hospital, Good Samaritan and Bon Secours Hospital Systems and developed nutrition programs for several sites including the Harford County Government, the Belair Athletic Club and Carefirst. She is a Certified Pump Trainer and Certified Diabetes Educator, specializing in renal nutrition.

Joanne Dielmann, RD, LD ,CDEJennifer Muller, RD, LD, CDE
Certified Diabetes Dietitian Educator


Ms. Muller has been a registered and licensed dietitian with the Geckle Diabetes and Nutrition Center since June 2004. She gained her certification as a diabetes educator in 2007, followed by her certification as an Animas Pump trainer in 2009. She graduated from the University of Maryland College Park and completed her internship at Johns Hopkins Hospital.

Ms. Muller reaches out to the community through Health Fairs, Support Groups and fund raising events held through the American Diabetes Association, as well as seeing outpatients in the Center at GBMC. She has taken a special interest in helping to educate patients with Polycystic Ovarian Syndrome.

Joanne Dielmann, RD, LD ,CDEKathy Noppinger, RN, MS, CDE
Certified Diabetes Educator


Ms. Noppinger received a BS degree from Towson University and a Master of Science degree, with a concentration on Diabetes Clinical Specialty, from University of Maryland. She received her certification in diabetes education in 2007 and her certification as an Animas Pump Trainer in 2009.
Her careers in diabetes management include residential nursing Camp Glyndon, provision of workshops as a consultant and volunteer with the American Diabetes Association, diabetes education fro Dr. Thaddeus Prout and pump training with Animus Corporation. She has been employed at Geckle Center since June 2004, where she provides not only education and management of Type 1 diabetes, Type 2 diabetes and Gestational Diabetes but also support groups and health fair screenings. She is an active member of the American Diabetes Association and the American Association of Diabetes Educators.

Dianna Cotterell, RN, BSN, MLA, MED, CDEDianna Cotterell, RN, BSN, MLA, MED, CDE
Certified Diabetes Educator


Ms. Cotterell received her Bachelor of Science degree from the College of Notre Dame of Maryland and earned her Master of Education degree from the University of Phoenix. She received her certification in diabetes education in 1988. Her career in diabetes education and management includes positions in Baltimore with the Joslin Diabetes Center Affiliate at the University of Maryland Medical System, MedStar Diabetes Institute and St. Agnes Hospital. She has a strong interest and a wealth of experience in the use of technology systems to assist persons with diabetes with self-care management. Additionally, Ms. Cotterell has an extensive background in homecare and case management. At GBMC, Ms. Cotterell is the inpatient diabetes specialist. Her main role is to work with hospitalized persons with diabetes to facilitate a seamless transition from inpatient to outpatient diabetes education and care.

Justin Kotler, MS, RD, LDN, CDEJustin Kotler, MS, RD, LDN, CDE
Certified Diabetes Educator


Mr. Kotler is a registered dietitian, licensed dietitian nutritionist and certified diabetes educator. He received a Bachelor of Science degree in Finance and a master's degree in Dietetics and Nutrition from Florida International University. Mr. Kotler's areas of expertise include diabetes, weight management, health and wellness, and sports nutrition. His experience includes positions as a coordinator of nutrition services at the Washington, D.C. Veterans Administration Medical Center and wellness coordinator for the CSX Transportation Wellness Project in Bloomington, Indiana. Additionally, Mr. Kotler has served as a nutrition and wellness coach in the Baltimore metropolitan area. He is a member of the volunteer faculty for Baltimore Fitness Academy (BMorefit) where he provides underprivileged youth with the nutritional knowledge needed for lifelong health.

Educational Staff:
Estelle Carter, BS, PA-C, CDE
Rebecca Denison, RD, LD, CDE, Doctor of Integrated Medicine
Joanne Dielmann, RD, LD ,CDE
Jennifer Muller, RD, LD, CDE
Kathy Noppinger, RN, MS, CDE

Administrative Staff:Linda Armetta, Senior Secretary
Tara Hegberg, Patient Services Assistant
Arteara (Tia) Watkins, Senior Secretary

Greater Baltimore Medical Center | 6701 North Charles Street | Baltimore, MD 21204 | (443) 849-2000 | TTY (800) 735-2258
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