Reproductive endocrinology and infertility (REI) is a surgical subspecialty of obstetrics and gynecology that trains physicians in reproductive medicine addressing hormonal functioning as it pertains to reproduction as well as the issue of infertility. While most REI specialists primarily focus on the treatment of infertility, reproductive endocrinologists are trained to also evaluate and treat hormonal dysfunctions in females and males outside infertility. Reproductive endocrinologists have specialty training in obstetrics and gynecology (ob-gyn) before they undergo sub-specialty training (fellowship) in REI.
Reproductive surgery is a related specialty, where a physician in ob-gyn or urology further specializes to operate on anatomical disorders that affect fertility.
In a number of countries, the pathway to become a subspecialist in REI is regulated. Thus, in the United States, for instance, the American Board of Obstetrics and Gynecology (ABOG) and American Osteopathic Board of Obstetrics and Gynecology set the standards for subspecialists to become certified. After four years of training in Obstetrics and Gynecology, a three-year approved fellowship needs to be successfully completed. Then, to become board certified in reproductive endocrinology and infertility, one must first complete board certification in obstetrics and gynecology (written and oral exams), and then certify in reproductive endocrinology and infertility (written and oral exams).
In the United States, fellowship in reproductive endocrinology and infertility usually takes 3 years, and is offered in 40 centers across the country as of 2013.