While continuing his studies at this institution, he received a TÜBİTAK scholarship, which enabled him to work for six months at the University of Alabama at Birmingham, home to one of the most competent teams in the field of Endocrine Surgery in the United States. During his time there, he worked with surgeons specializing in Thyroid, Parathyroid, and Adrenal Gland Surgery, such as Dr. Herbert Chen and Dr. Brenessa Lindeman, and participated in both surgeries and research activities.

After his time in the USA, he returned to his position at Ümraniye Training and Research Hospital.

Currently, he continues to provide the best possible service to his patients at Acıbadem Altunizade Hospital.

Dr. Mehmet Kostek is a member of the European Society of Endocrine Surgeons (ESES), the American Association of Endocrine Surgeons (AAES), the International Association of Endocrine Surgeons (IAES), and the Turkish Society of Endocrine Surgery. He was also accepted as a Fellow by the American College of Surgeons (ACS) following an evaluation and earned the FACS title. Dr. Köstek is a member of the Turkish Surgical Society and holds a Turkish Surgical Qualification Certificate. Dr. Köstek is married and has two children.