Meet the Fellows

Third-year Fellows

Holly Cooper, MD

Medical School
University of California, San Diego School of Medicine

Pediatrics Residency
University of California, Los Angeles

Growing up in the Bay Area, I was always drawn to science. As an undergraduate at Stanford University, I considered many different career avenues that would allow me to pursue this passion, including research, marine biology, veterinary medicine, and animal husbandry. Ultimately, I decided that a career in medicine would best allow me to combine my interest in applied science with my desire to have a direct and meaningful impact on the lives of those around me. After completing my master’s degree in biology at Stanford University, I took a year to work in clinical research and volunteer for an international medical non-profit before moving to Southern California to attend University of California, San Diego School of Medicine. It was in medical school that I first developed an interest in endocrinology, but it wasn’t until I was in pediatrics residency at University of California, Los Angeles that I was able to fully explore all that pediatric endocrinology had to offer as a field. I found myself enamored of the variety within the field, from diabetes to growth, thyroid to bone, puberty to pituitary, and everything in between. It was also in residency that I first learned that pursuing a career in pediatric endocrinology would afford me an avenue of working in gender medicine and with the LGBTQ+ community, something that had interested me long before I contemplated a career in medicine. 

As a pediatric endocrinology fellow at Stanford, I have honed my skills as a clinician and an educator while gaining exposure to the broad field of pediatric endocrinology and developing longitudinal relationships with my patients. I have been able to take part in providing gender care to children and adolescents and have worked alongside the diabetes research teams to introduce my patients to the rapidly evolving field of diabetes technology. Following fellowship, I hope to continue to work with gender diverse children, children with diabetes, and children with endocrine disorders. 

In my free time, I enjoy painting, mosaicking, sculpting, and working on other art projects. I also have a strong connection to the ocean and to nature and spend as much time as I can hiking or walking on beaches or the nearby Baylands trails. Although not entirely successful thus far, I have also been enjoying the slow process of turning my black thumb into a slightly green-tinged one while trying not to kill all the plants in my garden. 

Walter Zegarra, MD

Medical School
University of Miami Leonard M. Miller School of Medicine

Pediatrics Residency
University of Miami, Jackson Health System

I was born in Lima, Peru but grew up in Miami, Florida since I was 12 years old.  My father was a physician in Peru; thus, medicine was always in my mind growing up. I took a slight detour between college and medical school by becoming a Middle/High School Science teacher for 3 years. This was an amazing experience and reinforced my love for teaching and working with kids. Upon starting medical school at the University of Miami Miller School of Medicine, I knew pediatrics was the field for me.  I stated at the University of Miami for my Pediatrics Residency at Jackson Memorial Hospital/Holtz Children’s Hospital. It was during my residency elective rotations that I chose to do a month of pediatric endocrinology. After being exposed to the pathophysiology, teaching opportunities, and long-term management of endocrinologic conditions, I knew I had found my niche. I look forward to learning from leading experts in the Pediatric endocrinology field here at Stanford. My interests within endocrine are disorders of growth and management of type 1 diabetes. 

When I am not at work, I enjoy trying out new restaurants and sight-seeing the great places California has to offer. I am also trying to become more proficient in cooking without hurting myself, but it’s a work in progress! 

Second-Year Fellow

Connor Corcoran, MD

Medical School
University of Southern California, Keck School of Medicine

Pediatrics Residency
University of Vermont Medical Center, Burlington, VT

I grew up in a few different places but primarily in the St. Louis area before moving out west to study biology at the University of Southern California. After college, I had the good fortune to remain at USC for medical school to learn from the many wonderful patients and health professionals at its affiliated hospitals and solidify my desire to become a pediatrician. Through my pediatric residency training at the University of Vermont Children’s Hospital, I had the privilege to work with fantastic clinicians and families in general pediatrics and in various pediatric subspecialties. Increasingly I realized that pediatric endocrinology would enable me to partner with children and families longitudinally through growth and development while also navigating diabetes and other endocrine conditions of particular interest for me clinically.

Here at Stanford, I am thrilled to be part of such invested and collegial interdisciplinary teams in both endocrinology and diabetes. We are especially lucky to have so many colleagues interested in improving access to advancements in diabetes technologies to help decrease the burdens youth with diabetes and their families experience. Other areas of particular professional interest for me include growth, puberty, differences in sexual development, and youth with risk for multiple endocrine conditions, such as children with Prader-Willi syndrome (PWS) and survivors of childhood cancers. Outside of work, I enjoy spending time with my dog, playing the piano, watching comedy, and exploring the Bay Area with its many great restaurants, hiking trails, and museums.


Jennifer Ni, MD

Medical School
University of Pittsburgh School of Medicine

Pediatrics Residency
University of Texas Southwestern Medical Center, Dallas

I grew up mainly in the Bay Area of California, attending UC Berkeley for undergraduate (Go Bears!) with a major in Bioengineering. After a gap year working at a biotech start up, I traveled to the East Coast for medical school at the University of Pittsburgh, and then back to my birth state of Texas for residency at UT Southwestern. During my experiences in medical school and residency, I discovered that I enjoyed the logic of thinking through signaling pathways to understand the pathophysiology of endocrine disorders. In the future, I hope to combine my background in engineering with my passion for medicine to advance the field of endocrinology, especially in diabetes management. I am very excited to return to the Bay Area for fellowship in Pediatric Endocrinology. Outside of the hospital, I enjoy baking sweet treats, trying new restaurants, and running.

Luisa Valenzuela Riveros, MD

Medical School
University of California, Davis School of Medicine

Pediatrics Residency
Stanford University School of Medicine

I was born and raised in Bogotá, Colombia, I moved to the Central Valley of California in my early teens. Ever since then, California has been my second home. I majored in Neurobiology, Physiology and Behavior at UC Davis. I continued my medical education at UC Davis as part of the San Joaquin Valley PRIME program which allowed me to do my clinical years in the Central Valley. This experience allowed to delve deeper in the unique health challenges rural families face and cultivated my passion for pediatrics. I completed pediatrics residency at Stanford where I was part of the medical education scholarly concentration and LEAD (Leadership Education in Advancing Diversity). My interests include medical education, research in healthcare delivery, disparities in management of endocrinological disorders in vulnerable communities, as well as diabetes technology development. In my free time I enjoy exploring the outdoors, spending time with family/friends and baking.

Fellowship Program

Recent Graduates


Ananta Addala, DO, MPH - Instructor, Pediatric Endocrinology and Diabetes at Stanford University