|He received his medical training at the Hacettepe University Faculty of Medicine (M.D.). After completing his specialization in Internal Medicine Department at Erciyes University Faculty of Medicine, he started to work as assistant professor at the same university in 1988 and a professor in 1995. He has worked in the Department of Endocrinology at London University St.Bartholomew's Hospital and Istanbul University Cerrahpasa Medical Faculty.
Between 2006-2008 he was the chairman of The Society of Endocrinology and Metabolism of Turkey (SEMT). He has been a board member of The European Neuroendocrine Association (ENEA) between 2002-2006, and The European Society of Endocrinology (ESE) between 2005-2009. In 2008, he was among in the founders and in administration of The Turkish Neuroendocrinology Association. He was an advisory board member of The European Neuroendocrine Tumor Society (ENETS). In 2015 he was elected to the board of the Pituitary Society. He was brought to full membership of Turkish Academy of Sciences (TUBA) and has worked for two terms as a council member of TUBA.
His main fields of interests are neuroendocrinology, reproductive endocrinology and pituitary, and he has focused especially on traumatic brain injury-induced neuroendocrine changes in recent years. Kelestimur and his team have shown at first time, that head injuries in kickboxing and boxing can cause damage to the pituitary gland, which affects the body's metabolism and stress response. He has delivered more of 100 speech by invitation at International Congresses. His current H-index is 42 and he has published more of 270 papers in International Journals. Between the years 2008-2015 he served as the Erciyes University Rector and he is the founder of Health Institutes of Turkey.