Baylor Scott & White Endocrinology Specialists –McKinney is the medical practice for Dr. Vivienne Yoon, Dr. Jennifer St. John and Dr. Sana Ullah. All Providers are board-certified in fellowship-trained in general endocrinology, diabetes and metabolic disorders. The providers specialize in the treatment of adult endocrine disorders, thyroid disorders, diabetes mellitus (Type 1 and 2) and pituitary dysfunction. Call today to schedule an endocrinology appointment with one of the physicians near you in McKinney.