Meet Our Care Team
Thousands of patients, over a decade of experience.
Consult with the Experts
Our care team has extensive experience in hormone restoration, sexual health treatment, and integrative wellness. They’re passionate about helping patients improve their lives and feel their best.
Defy Medical’s care team is led by Dr. Justin Saya, our medical director and lead practicing physician.
Medical Director and Lead Practicing Physician
Justin Saya, MD
Dr. Justin Saya graduated as class valedictorian from North Carolina State University with a dual bachelor’s degree in Biological Sciences and a bachelor’s degree in Economics. He received his medical degree from the University of North Carolina at Chapel Hill, School of Medicine, and subsequently performed his internship and residency training at the University of South Florida/Morton Plant Mease Family Medicine Residency Program.
In addition to his education and training, Dr. Saya is privileged to hold many certifications, honors, and memberships, including membership to the American Medical Association, the American Association of Family Practitioners, and the World Anti-Aging Academy of Medicine, among many others.
Dr. Saya offers therapy to both men and women who are looking to balance their hormone levels and improve their overall quality of life. His patients have reported benefits such as improved energy levels, restored libido, improved muscle tone and exercise tolerance when combined with an exercise routine, healthy/sustainable weight loss when positive eating and exercise habits are adapted, and much more.
He hears repeatedly from Defy patients that hormone replacement therapy is one of the best decisions they’ve ever made.
Caleb Calkins, MD
Dr. Calkins is focused on optimum health for his patients. He believes in a proactive approach to medicine that emphasizes maintaining an appropriate balance of nutrition, hormones, and fitness. He is dedicated to finding the root causes of his patient’s symptoms and the appropriate treatment regimens for complete wellness.
Dr. Calkins completed his bachelor’s degree in Public Relations with a minor in Nutritional Science at the University of Florida. While there, he was involved with research focused on the benefits of a ketogenic diet in improving epilepsy. He received his medical degree from St. Matthews University, and subsequently performed his internship and residency at Tulane University/East Jefferson General Hospital Family Medicine Residency Program in New Orleans, Louisiana. In addition, he received a master’s degree in Hospital Administration from Davenport University in Grand Rapids, Michigan.
Throughout his education and experience, Dr. Calkins has seen the benefit of using multiple modalities to improve patient outcomes.
Krystle Alvarez, FNP-C, FNP-BC
Krystle Alvarez, FNP-C, FNP-BC, is a dual board-certified Family Nurse Practitioner with an extensive background in patient care. Before becoming a Nurse Practitioner, she spent more than a decade working as a Registered Nurse in the emergency room, where she gained experience caring for patients with a wide variety of medical needs.
As a Nurse Practitioner, Krystle transitioned into wellness-focused medicine, gaining experience in weight management, Hormone Replacement Therapy, Peptide Therapy, and aesthetics. She has long had an interest in preventative care and believes in looking at the whole picture when working with patients, rather than focusing on a single symptom or concern.
Krystle’s approach to care centers on understanding each patient as an individual and creating personalized treatment plans that fit their unique needs and goals. She strives to create an environment where patients feel comfortable discussing all aspects of their health and feel supported in finding an approach to care that works best for them.
Born in Colorado and raised in Florida, Krystle enjoys spending time with her husband and two children. Outside of patient care, she enjoys Disney, yoga and dance classes, and trips to the mountains where she can spend time in nature and slow down with her family.
Beth Bray, APRN
Beth Bray, APRN, comes to Defy with over two decades of medical experience. She started her career after graduating from Prairie State College and became a Registered Nurse where she worked in hospital settings for orthopedics and oncology.
In 2015, she completed her graduate degree from Northern Illinois University and began working in Primary Care and Integrative Holistic Care.
Beth cites the importance of forming a partnership with her patients to help them work towards optimal health goals and allowing them to live their absolute best lives. Additionally, Beth feels that Defy is on the cutting edge of hormone replacement therapy and integrative wellness.
Beth recently made the trek from icy Illinois to sunny Florida and became a member of the Defy Medical team in February of 2021. Since moving to Florida, she’s developed a passion for gardening and just about anything else the Florida sunshine has to offer. Beth is also an avid reader and is usually zipping through an Octavia Butler Sci-Fi novel in her free time.
Morgan Bulawa, PA-C
Morgan is a Board-Certified Physician Assistant with a strong passion for empowering patients to optimize their health through education and personalized care. A graduate of the University of Houston, she earned her degree Magna Cum Laude while playing collegiate soccer. Morgan then pursued her Master’s degree from the Texas Tech University Health Sciences Center PA program, where she was inducted into the Pi Alpha Honor Society.
Before embarking on her PA career, Morgan was introduced to bioidentical hormone therapy in 2021 through clinical experiences at two different HRT clinics in Texas. Her dedication to hormone optimization grew from these hands-on experiences, and her interest was further shaped by family influence—her uncle and aunt, both pharmacists specializing in HRT, have played a key role in shaping her approach to hormone therapy.
Morgan’s commitment to wellness extends beyond her professional life. With a background in Exercise Science and a passion for staying active, she incorporates her experience with fitness and sports into her treatment plans. Born in Norway but raised in Texas, Morgan enjoys spending her free time at the Florida beaches with her husband.
Corbin Burns, PA-C
Corbin Burns, PA-C, joined Defy Medical with a strong foundation in both emergency medicine and behavioral health. He earned his bachelor’s degree in Biology from Birmingham-Southern College in 2014, followed by a master’s degree in Physician Assistant Studies from the University of Alabama at Birmingham in 2017.
Corbin has long held a professional interest in hormone replacement therapy and testosterone optimization, particularly through a holistic and integrative lens. His approach to patient care is centered on helping individuals achieve long-term wellness by addressing root causes, lifestyle factors, and individualized goals.
Now based in Florida, Corbin spends his free time with his partner and their golden retriever. Outside of the clinic, he enjoys exploring new restaurants, spending time at the beach, and connecting with friends over good food and conversation.
Robin Cozine, APRN, FNP-C
Robin Cozine, APRN, FNP-C, is an experienced Advanced Practice Registered Nurse who brings a wealth of expertise in wellness, medical leadership, and patient-centered care. She holds a Master of Science in Nursing from Austin Peay State University and is board certified as a Family Nurse Practitioner by the American Association of Nurse Practitioners. Licensed in multiple states, Robin has practiced across diverse specialties, including functional wellness, medical aesthetics, weight management, and hormone balancing.
Robin has served in leadership roles throughout her career, from starting up wellness practices to training and mentoring other providers. Her approach combines comprehensive health assessments with personalized lifestyle interventions, focusing on restoring balance and optimizing long-term health for each patient. She has extensive experience in Bioidentical Hormone Replacement Therapy, medical weight loss programs, and intravenous and injectable treatments.
Outside of the clinic, Robin enjoys an active and creative lifestyle. She has performed locally and internationally as a majorette with several adult marching bands — an experience that reflects her passion for teamwork, dedication, and bringing energy to everything she does. Whether in the exam room or on the field, Robin’s goal is to inspire others to live with vitality and confidence.
Catherine Fermin Jimenez, MSN, APRN, FNP-C
Catherine is a bilingual Family Nurse Practitioner with a passion for helping people look and feel their best. Born in New York City and raised in Southwest Florida, she is proud to still call Southwest Florida home.
Catherine earned her Bachelor of Science in Nursing from Chamberlain University in 2020, graduating with President’s Honors, and went on to complete her Master of Science in Nursing as a Family Nurse Practitioner in 2023. Before becoming an Advanced Practice Registered Nurse, she spent six years working as a registered nurse in oncology, where she developed a deep appreciation for compassionate care, meaningful patient relationships, and the importance of treating every person as an individual.
Her clinical background includes hematology and oncology, functional medicine, hormone optimization, medical weight management, preventive wellness, and aesthetic medicine. She strives to make every patient feel comfortable, heard, and empowered throughout their healthcare journey. As a bilingual provider fluent in English and Spanish, she enjoys connecting with patients from diverse backgrounds and helping them feel at ease.
Outside of the clinic, Catherine is a busy mom who spends much of her time cheering on her kids at the baseball field. When she isn’t at a game or practice, she loves being outdoors and making memories with her family.
Megan Kershner, MSN, APRN, AGNP-C, MSCP
Megan Kershner, MSN, APRN, AGNP-C, MSCP, received her Master of Science in Nursing from the University of South Florida in 2021.
She is a Menopause Society Certified Practitioner by The North American Menopause Society. Megan is also certified by Biote, a leading innovator in precision and preventive health care, to place HRT pellets.
Megan is pursuing continuing education in Hormone Replacement Therapy, diabetes, and functional nutrition, to provide patients with the most up-to-date care and support.
In her free time, Megan loves traveling with her husband, reading, gardening, and making sourdough bread.
Mike Linkous, PA-C
Mike Linkous, PA, completed his bachelor’s degree in Adult Fitness/Exercise Science at Marshall University in West Virginia. He received his Physician Assistant degree from The College of West Virginia in Beckley, West Virginia in 2000. Since then he has worked in Sports Orthopedics, Family Medicine, Integrative Hormone Medicine, and Pain Management.
As a member of the Defy Medical provider team, Mike takes an integrative approach to treating patients. In addition to his extensive medical training and practice, Mike also brings unique personal perspective to his patient consultations as he has been on TRT for more than 15 years.
Michelle Maiolo, FNP-BC
Michelle Maiolo, FNP-BC, has been providing direct patient care since 2003. She has worked in a variety of settings, including oncology, women’s health, outpatient surgery, and urgent care. After a long, rewarding career as a Registered Nurse, Michelle earned her master’s degree from Purdue University Global and became a Family Nurse Practitioner (FNP).
Her experience in pain management and addiction medicine highlighted gaps in today’s healthcare culture and motivated her to pursue a more patient-centered, holistic approach. With a focus on optimized hormones alongside nutrition and exercise, Michelle strives to serve as a guide for patients as they work toward their wellness goals. She values that Defy Medical allows providers the time to truly understand each patient’s priorities and provide education that empowers individuals to build a plan of care that fits their needs.
Michelle is a proud member of the American Association of Nurse Practitioners, the Tampa Bay Advanced Practice Nursing Council, and the West Coast Advanced Practice Nursing Council.
Originally from Rochester, New York, Michelle is a die-hard Buffalo Bills fan who moved to Florida in 2019. When she is not working from home with her three dogs, she enjoys spending time outdoors with family.
Marisa Palles, PA-C
Marisa Palles, PA-C completed her Bachelor of Science degree at the University of South Florida in 2018. She then graduated Magna Cum Laude from South University in 2022 with a master’s in Physician Assistant Studies.
Marisa has clinical experience in the urgent care setting and has seen an array of complex medical conditions, but her true passion is in the field of endocrinology. Prior to completing her education as a PA, she assisted Defy Medical patients as a Patient Services Specialist. Now Marisa is thrilled to continue helping Defy Medical patients as a member of the care team.
Marisa’s approach to hormone optimization is centered around patients’ symptoms as well as lab values. She strives to implement her own healthy lifestyle into her practice and takes a holistic approach toward improving patients’ quality of life outside of just hormone imbalance.
Marisa is a member of Florida Academy of PAs (FAPA) and is a National Commission on Certification of Physician Assistants (NCCPA) board-certified PA.
She was born and raised in the Tampa Bay area. Her interests include trying out new exercise routines like resistance and strength training, HIIT, and Pilates.
Elizabeth “Liz” Thara, APRN, FNP-C
Elizabeth “Liz” Thara, APRN, FNP-C is a committed Advanced Practice Registered Nurse with a rich background in healthcare, having earned her Bachelor’s degrees in Biology (2010) from St. Xavier University Chicago and Nursing (2012) from Loyola University Chicago. She went on to earn her Master of Science in Nursing from Chamberlain University in 2022. With over a decade of experience as a Registered Nurse in labor and delivery, Liz has developed a deep passion for Women’s Health as well as wellness and weight management.
In her current role as a Nurse Practitioner at Defy Medical, she is expanding her expertise into Men’s Health, an innovative area that excites her as she continues to grow in her field. Liz believes in treating each patient as a unique individual, listening carefully to their needs, and working together to create personalized care plans. She is committed to learning from her patients to ensure they feel heard and supported throughout their wellness and hormone therapy journey.
Outside of her professional life, Liz enjoys an active lifestyle in Florida, where she lives with her fiancé, Matt, and their mini-golden doodle, Sunny. For her, a perfect day is one where the sun is shining, the sky is blue, the water is calm, and she can enjoy time outdoors with friends and family.
Alexis Voke, PA-C
Alexis Voke, PA-C, was born in Dallas, Texas, and grew up in South Florida. She earned her bachelor’s degree in Exercise Science from Florida State University before continuing her education at Touro College in New York City, where she earned a bachelor’s degree in Health Sciences and a master’s degree in Physician Assistant Studies. During her training, Alexis gained extensive clinical experience while completing rotations throughout all five boroughs of New York City.
Throughout her career as a Physician Assistant, Alexis has gained significant experience in internal medicine, hormone replacement therapy, and weight management. She has helped manage the care of thousands of patients, giving her broad experience working with individuals across a wide range of health needs, goals, and stages of their wellness journey.
Alexis focuses on creating individualized treatment plans that support lasting wellness, improve overall quality of life, and empower patients to take an active role in achieving their personal health goals. She values an approach to care that considers each patient’s individual needs and helps create a plan that can support meaningful, sustainable progress over time.
Outside of patient care, Alexis enjoys boating on the ocean, taking heated HIIT workout classes, and spending time with her golden retriever.
Ben Walker, APRN, DC
Ben Walker, APRN, DC received his Doctor of Chiropractic degree in 1989 and has been a nurse practitioner since 2014.
His interest in the integrative approach to healthcare inspired him to explore and understand the many facets of optimizing personal health. When working with his patients, Ben applies his years of medical knowledge and practice to understand the physical, nutritional, and emotional aspects of a patient’s lifestyle.
Ben himself has been on bio-identical hormone replacement therapy for the past 4 years and has had the opportunity to get acquainted with the many benefits of a thorough and comprehensive approach to using HRT as a means to restore a patient’s overall well-being. His in-depth and personal experience with integrative healthcare allows him to truly understand the various needs of his patients.
What Patients are Saying
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“Alexis was great at going over my labs…”
Visited on October 20, 2026
Alexis was great at going over my labs and current medications. I feel better than ever under Defy’s care.
–PAYTON C
“I see Beth & i really like her”
Visited on October 22, 2026
I see Beth & i really like her. She listens to me and takes the time needed to answer my questions. Shes open to me trying new or different medications. I have felt so much better and happy with my protocol.
–L C
“Prompt and informative”
Visited on October 24, 2026
Prompt and informative
–LANZA,MARIE
“Great”
Visited on October 23, 2026
Ben is very knowledgable and spends time going over everything. I never feel rushed or leave with questions.
–Vinnie D
“Love Defy!”
Visited on October 23, 2026
Beth is so helpful and infomative!
–Beganskas,Karissa
“I loved Ben”
Visited on October 25, 2026
I loved Ben! He was informative, truly interested and I didn’t feel rushed! All around good visit!
–Robyn
“Robin was great”
Visited on October 23, 2026
Robin was great. She answered all my questions and was a joy to talk with.
–MARK
“Excellent”
Visited on October 26, 2026
Excellent. Very knowledgeable and thorough.
–MAIDA,ANJANETTE
“Michelle”
Visited on October 25, 2026
Michelle, APRN, was great. She was very thorough, helpful, and patient with all my questions. I would highly recommend her.
–GONZALES,SHEILA
“Capable and knowledgeable!”
Visited on October 26, 2026
The physician was on time for the apointment, she was pleasant and professional. She’s very knowledgeable and she explained everything in detail to me.
–VINCENT YUE