Qualifications
So much school!
Plan on spending the rest of your teens and 20s in college; maybe even a year or two of your 30s as a resident (student/doctor or trainee).
You'll have to be really good at math and science, especially biology, chemistry, and anatomy. Biochemistry is likely to be your undergrad major. That, or straight up biology.
You're going to have to be tops in your class, pass the MCATS with flying colors, and get into a med school that offers a top notch endocrinology program. From there you'll do a residency fellowship in a distinguished endocrinology program and pass the Medical Board Licensing Exam.
This might not be the career path for you if, instead of studying all the time, you'd rather play rugby or video games.