Our Mission
At Amity Health, our mission is to rekindle the bond between patients and doctors through the delivery of Direct Primary Care (DPC) in Orange County. We are dedicated to offering personalized, comprehensive, and patient-centered healthcare with an emphasis on innovation and accessibility.
Our Team
I grew up here in Orange County and attended Villa Park High School. Following my roots, I pursued higher education, earning my Bachelor of Science in Biopsychology at the University of California, Santa Barbara. My journey in healthcare began at California Northstate University, College of Medicine, where I completed my medical education.
Driven by a desire to make a meaningful impact in patient care, I embarked on my residency training journey. Initially, I delved into General Surgery at U.C. Davis Medical Center in Sacramento, gaining valuable experience in the surgical realm. However, my true calling emerged as I transitioned to specialize in Family Medicine through UC Davis's satellite program in Modesto, CA.
Frustrated with the challenges posed by the corporate and insurance-driven healthcare system, I founded Amity Health with the vision of revitalizing family medicine. Committed to restoring the doctor-patient relationship, my team and I prioritize the compassionate foundation on which medicine was built.
Outside of my professional pursuits, I find joy in motorsports, particularly Formula 1, and hockey. Cherished moments include spending time with my wonderful border collie, Remy.
Board Certified Family Medicine
Dr. Trevor Tsay, MD
Dr. Cindy T. Yang, MD
Hi, I’m Dr. Cindy Yang, and I’m excited to be a part of Amity Health! I believe great healthcare should feel unrushed, personal, and grounded in real partnership. My goal as a physician is to help you understand your body, address the root causes of illness, and build lasting health — not just mask your symptoms.
I grew up in Orange County, and it’s a privilege to now care for the same community that shaped me. I earned my degree in Human Biology from UC San Diego (Summa Cum Laude), attended medical school at Boston University, and completed my Family Medicine residency at UC Irvine, where I also served as chief resident.
I chose Family Medicine because I value long-term relationships and caring for the whole person across every stage of life. My experience in primary and urgent care reinforced how essential time and accessibility are to good medicine, which is why I practice Direct Primary Care. I place strong emphasis on understanding the lifestyle factors that shape health, such as sleep, stress, nutrition, and daily routines, as these often play a central role in chronic conditions such as diabetes, hypertension, and fatigue. I’m currently pursuing fellowship training in Integrative and Functional Medicine at UC Irvine, where I combine evidence-based medicine with deeper, thoughtful evaluation.
If you’re looking for a physician who will take the time to listen, think deeply about your health, and build a long-term partnership in your care, I would be honored to work with you.
Board Certified Family Medicine
Cristina Terwilliger brings a personal passion for functional nutrition to Amity Health Direct Primary Care, inspired by the profound improvements it brought to her own health. She helps patients uncover the root causes of symptoms through individualized, science-based nutrition and lifestyle strategies. Cristina integrates advanced functional testing—including GI-MAP gut microbiome analysis—to guide personalized plans for digestion support, inflammation reduction, hormone and thyroid balance, stress recovery, and immune optimization. With a supportive, patient-centered approach, she empowers individuals to understand their bodies, make meaningful changes, and achieve sustainable long-term wellness.
Cristina Terwilliger
Functional Nutritionist, RN
I grew up in the Inland Empire receiving a bachelor's in environmental science from UC Santa Barbara and later receiving a Master’s in Business Administration from UC Riverside. I have been very active in my life doing everything from surfing, snowboarding, weightlifting, Brazilian Jiu Jitsu, and more. My health is something I have always valued highly as it has allowed me to delve myself into so many passions. Having had many injuries and being a patient through many insurance based systems, the 10 minute appointments and advice to stop doing the things I love were the reasons I found Direct Primary Care so fascinating. It allows patients to have a relationship with their doctor who thoroughly cares about the well-being of their patients. When Trevor approached me to help manage the practice, I was thrilled at the opportunity to be able to give patients a level of care that I was unaware was even possible in the current medical landscape.