Leonid Poretsky MD
Gerald J. Friedman Diabetes Institute
Wikipedia page

Pamela Flores,

Gerald Bernstein, MD
Diabetes Management Program


Dr. Gerald Bernstein graduated from Dartmouth College and Tufts University  School of Medicine. He is board Certified in Internal Medicine (1966) and Endocrinology (1973). After 2 years of military service and 2 years of research fellowship he entered practice in 1966. He served as President of the American Diabetes Association from 1998-1999 following more than 20 years of committee work and chairmanships. He joined ADA’s board of directors in 1994. While president he instituted the first study group for Type 2 diabetes in adolescence. In 1995 he established a diabetes education program for a group of Manhattan physicians. In 1999 he established and became director of an educator based diabetes education and management program at Beth Israel Hospital in New York. In 2006 with the Chief of Endocrinology, they obtained a $5 million grant to establish the first Friedman Diabetes Institute. This was staffed by diabetes educators of all types including nutrition, exercise, psychology including structured programs to go with them.  The Institute moved to the Department of Endocrinology at Lenox Hill Hospital, part of Northwell Health Care. Part of the mission is not only to serve patients but to continually upgrade the professional capabilities of the staff. Dr. Bernstein has been an Associate Clinical Professor of Medicine at the Albert Einstein College of Medicine and The Mount Sinai School of Medicine as well as an Attending Physician at Montefiore Medical Center, Einstein College Hospital and Lenox Hill. He has emeritus status at all of the above. He is the author of many papers scientific and clinical and coauthored the book “If it runs in your family”. He also served as Vice President for Medical Affairs at Generex Biotechnology.

Edward Merker, MD
Staff Endocrinologist

Luisa F. González Ballesteros, MD
Pediatric Endocrinologist

Agustin Busta, MD
Assistant Director,
Gerald J. Friedman Diabetes Institute


Dr. Agustin Busta received his medical doctor degree from the Federico Villareal National University in Lima, Peru. He completed internal medicine residency training at New York Medical College—Cabrini Medical Center, and a fellowship in endocrinology and metabolism at New York University Medical Center. He is board certified in internal medicine and in endocrinology and metabolism. He was a faculty member at Bellevue and NYU Langone Medical Center and also served at Beth Israel Medical Center as the director of diabetes section and clinical trials unit. At Beth Israel he was promoted to the rank of Associate Professor of Medicine. In 2017 he joined the Northwell Health Physician Partners – Endocrinology at Lenox Hill Hospital as the Assistant Director of the Gerald J. Friedman Diabetes Institute. Dr. Busta has been a practicing endocrinologist for over 25 years with focus on diabetes in pregnancy and type 1 and type 2 diabetes. He also has expertise in adrenal, pituitary, thyroid and parathyroid disorders. He is a dedicated clinician and educator, with published manuscripts and book chapters, and is well respected in the endocrine community.

Marina Krymskaya, NP
Assistant Director,
Gerald J. Friedman Diabetes Institute


Marina Krymskaya is an Assistant Director of the Gerald J. Friedman Diabetes Institute in the Department of Medicine at Lenox Hill Hospital. She is a Board Certified Adult Nurse Practitioner, and Certified Diabetes Educator. Marina obtained her undergraduate degree from Molloy College, and her graduate degree from Hunter College in New York. At work, Marina progressed from Staff Nurse to Diabetes Educator, Research Coordinator, Assistant Director. Mrs. Krymskaya is an author of the chapter on the resources for people with diabetes in the “Principles of Diabetes Mellitus” textbook. She has been co-investigator and coordinator of various research studies, and provided multiple presentations, including ones for ADA, and New York City Department of Health and Mental Hygiene. Marina Krymskaya is a recipient of OTTY Award.

Maria Pajares, RN
Nurse Educator


Maria Pajares, RN is a diabetes nurse educator with over 34 years of experience. She is a graduate of the National University of Cajamarca, Peru where she received her bachelor’s degree in nursing, and also from the National University Federico Villarreal, where she obtained her masters in nursing. Upon relocating to the United States, her passion for nursing continued and she attended the Beth Israel Nursing School Program for International Nurses where she was awarded a certification in conjunction with the University of the State of New York Education Department. Before joining the Diabetes Institute, she had a diverse background which included critical care, neonatal nursing and pediatrics. She believes in patient-centered care and educates patients of all ages how to manage their diabetes diagnosis. Maria is a member of the American Association of Diabetes Educators and the American Diabetes Association.

Chui Pereda, RD
Registered Dietitian


Chui Pereda, RD, CDE, CDN is a New York-based registered dietitian and certified diabetes education. She obtained her bachelor’s of science degree at Cornell University and completed her dietetic internship at Queens College. After completing her internship, she worked as a community dietitian in Special Supplemental Nutrition Program’s WIC and then as a clinical dietitian at North Central Bronx Hospital. She currently works at Northwell’s Friedman Diabetes Institute where she specializes in diabetes education and weight management. In her spare time, she enjoys running around the reservoir in Central Park.

Natalie Morrow, LCSW
Social Worker


Natalie Morrow, LCSW is the practice social worker in the department of medicine for the Gerald J. Friedman Diabetes Institute, the Gerald J. Friedman Transgender Health and Wellness Program and the endocrinology division at Lenox Hill Hospital. She is a licensed clinical social worker who received her master’s degree in social work from New York University and continued her education with a two year training program at New York Psychoanalytic Institute in psychodynamic psychotherapy. Prior to getting her masters, Natalie attended a two year program at the East West Institute for Holistic Health studying alternative approaches for treating the mind, body and spirit. She has spent the bulk of her career as a medical social worker, beginning as a hospice social worker and moving on to work with those with chronic illnesses. Throughout her career Natalie has continued to study diverse philosophies and teachings and over the years has developed a deep understanding of what patients and their families go through. It is her goal to provide support and assistance with empathy and compassion so individuals may work towards living their best lives.

Dimiter Avtanski, PhD
Research Laboratory

AVTANSKI, Dimiter Ph.D.

Dimiter Avtanski is a director of the endocrine research laboratory at Friedman Diabetes Institute at Lenox Hill Hospital in New York City, and an assistant professor of medicine at Donald and Barbara Zucker School of Medicine at Hofstra/Northwell in Hempstead, New York. Dr. Avtanski received his master’s in science degree in biology and chemistry from Sofia University in Bulgaria and his Ph.D. degree from the Bulgarian Academy of Sciences in collaboration with Beth Israel Medical Center at Albert Einstein School of Medicine in New York City. Before joining Friedman Diabetes Institute, Dr. Avtanski specialized at the University of Leipzig, Germany and completed seven years of post-doctoral fellowships at The Johns Hopkins University School of Medicine in Baltimore, Maryland. His main research focuses on the interactions between obesity, diabetes, carcinogenesis, and steroidogenesis. Dr. Avtanski serves as an associate editor for Molecular Medicine journal, is reviewing for multiple scientific journals, and was recognized as an outstanding reviewer for Metabolism and Nutrition, Metabolism and Cardiovascular Diseases journals. He is a research mentor of rotating fellows from Lenox Hill Hospital, The Feinstein Institute for Medical Research, and Hofstra University.

Gail Kaplan, RD
Practice Dietitian Nutritionist


Gail Kaplan, RD is a practice dietitian at the Gerald J. Friedman Diabetes Institute at Northwell Health. She holds a bachelor of science in nutrition from the University of Massachusetts Amherst, and completed the dietetic internship program at Bluffton University. Gail believes that nutrition education should be accessible to all people as a tool for disease prevention and treatment. She enjoys promoting a healthy lifestyle through nutrition and exercise. At the Friedman Diabetes Institute, Gail provides nutrition guidance to patients and their families. She shares her passion for cooking, while leading monthly cooking demonstrations using healthy ingredients. In her free time, Gail likes to read, crochet, visit museums, and explore the city. She can always be found in the kitchen trying new recipes.

Conrad Sanchez
Exercise Consultant

SANCHEZ, Conrad Exercise Consultant

After a few years of working in finance, I switched careers because I have experienced first-hand, and through others, the multitude of physical, mental, and spiritual benefits that a progressive, well-designed training program can offer. I collaborate with individuals looking to make healthy lifestyle changes, and provide them with the necessary tools and guidance to obtain their fitness goals. In my childhood, I enjoyed playing sports, especially basketball, inspired by my father who was a professional basketball player. I knew then that sports would always be part of my life, and as I grew older I became drawn to the union of athleticism and health. This, in combination with my penchant for helping others led me to my career path in personal training. After graduating in the top 5% of my class at the American Academy of Personal Training in New York City, I took my first job at a high-end gym. I then had the opportunity to work with top industry leaders and gained a wealth of knowledge and expertise. Today, in stark contrast to my days in finance, every morning I wake up excited to work with a broad spectrum of enthusiastic and motivated individuals seeking fitness training in a number of different areas. My personal philosophy is to do what you love and to always be learning. I continue to learn by attending as many seminars, conferences and fitness workshops as possible. Furthermore, I have a Master’s degree in Kinesiology from the A. T. Still University. I am fluent in Spanish, French, English, and German, as well as a little Basque.

Marilyn Jefferson
Fellowship Program Coordinator

Sandra Miranda
Billing Coordinator

Karina Ziskovich
Research Coordinator


Since July of 2016, I have been working as a Clinical Research Coordinator for the division of endocrinology at Northwell Health Physician Partners at 59th Street. My current projects include an NIH trial and several pharmaceutical trials. Prior to joining Northwell Health, I had been working in the administrative sector at Mount Sinai Beth Israel Medical Center for about 8 years. I was excited to switch gears and embark on a different role as a Clinical Research Coordinator for the D2d study at Lenox Hill Hospital. The D2d study investigates whether Vitamin D slows the progression to diabetes for patients who have prediabetes. Every day has been a learning experience for me and I enjoy advancing my skills in clinical research and am grateful for the opportunity to work with the Friedman Diabetes Institute staff. I regard the Friedman Diabetes Institute team as a wonderful team of healthcare professionals and am truly happy to work and learn from them on a daily basis. I genuinely enjoy interacting with patients and in my experience found that exhibiting enthusiasm and concern for each patient is the key to succeeding in the challenging tasks of clinical research recruitment and retention. I consider myself a dependable individual who is respectful and caring towards others. I hold a BBA degree from Pace University in Management Information Systems.

Ruthie Perez
Research Supervisor

PEREZ, Ruthie

Ruthie Perez graduated with her master’s in science in Allied Health Studies from the College of Mount Saint Vincent in Riverdale, NY. She has over 10-years of research experience. She joined Northwell Health in July 2017 as a Research Supervisor at Lenox Hill and works on diabetes and endocrine studies. Previously, she was a Senior Research Coordinator at Mount Sinai Hospital for over 9-years working on multiple sclerosis studies.