Dr. Tsutsui was awarded his Ph.D. degree from Waseda University, Tokyo, Japan in 1981 and joined the Faculty of Integrated Arts and Sciences, Hiroshima University, Japan. He became Professor at the Faculty of Integrated Arts and Sciences, Hiroshima University in 1996 and Director of Center for Integrative Brain Sciences at Hiroshima University in 2000. He recently joined as Professor the Department of Biology, Waseda University in 2006.

Dr. Tsutsui has established himself as one of the leaders in the field of Neuroendocrinology by his distinguished academic career. He has contributed to the advancement of Neuroendocrinology by a series of his studies over the past four decades by focusing on the discovery of novel neurohormones, such as neurosteroids and neuropeptides, and the demonstration of their mode of actions and functional significances. 

In 1995, Dr. Tsutsui first found de novo neurosteroidogenesis in the avian brain from cholesterol and subsequently demonstrated the biosynthetic pathway of neurosteroids using quail. He also discovered that the Purkinje cell, an important brain neuron, is a major site for neurosteroid formation in the brain. The promotion of neuronal growth, spinogenesis and synaptogenesis and the modulation of synaptic neurotransmission by neurosteroids have been found by his studies on birds and mammals. More recently, Dr. Tsutsui has further identified 7a-hydroxypregnenolone as a novel bioactive neurosteroid in the brain of vertebrates. He has also demonstrated that 7a-hydroxypregnenolone acts as a key factor for inducing locomotor activity and melatonin regulates synthesis of this novel neurosteroid, thus inducing diurnal locomotor changes. Thus, the discovery of 7a-hydroxypregnenolone and its role in mediating the action of melatonin have improved our understanding of the molecular mechanisms underlying locomotor rhythms. 

Dr. Tsutsui is also known as the discoverer of gonadotropin-inhibitory hormone (GnIH). Gonadotropin-releasing hormone (GnRH) is known to be the primary factor responsible for the hypothalamic control of gonadotropin secretion. However, a neuropeptide inhibitor of gonadotropin secretion was, until recently, unknown in vertebrates. In 2000, Dr. Tsutsui discovered GnIH as a novel hypothalamic neurohormone in quail. Subsequently, he and his colleagues demonstrated that GnIH inhibits gonadal development and maintenance by decreasing gonadotropin synthesis and release in quail. His tremendous studies of GnIH have demonstrated that GnIH is an important factor in the control of avian reproduction. Thus, the discovery of GnIH has opened a new research field in reproductive neuroendocrinology from a novel standpoint. Furthermore, he has identified GnIH in the brain of other vertebrates. He and colleagues have also demonstrated that a similar gonadotropin-inhibitory system is present in mammals and fish. He and colleagues have further discovered that melatonin regulates the synthesis of GnIH. This novel mechanism indicates that GnIH is capable of transducing photoperiodic information via changes in the melatonin signal, thereby influencing the reproductive axis. GnIH studies are currently in progress by many laboratories throughout the globe.  

Dr. Tsutsui has published an impressive set of over 390 papers in first rank journals including Nature Medicine, Nature Communications, Proc. Natl. Acad. Sci. USA, Frontiers in Neuroendocrinology, Progress in Neurobiology, Mass Spectrometry Reviews, Endocrinology, J. Neuroendocrinol., J. Molecular Endocrinology, J. Neuroscience, J. Neurochemistry, Molecular Neurobiology, Neuroscience, Biochemical J., FASEB J., British J. Pharmacology, Scientific Reports, etc.]. He has given more than 97 invited lectures including plenary lectures at international congresses and symposia. His distinguished research achievements have also been described in many excellent review papers including Nature Reviews Neuroscience (2005), Mass Spectrometry Reviews (2005), Endocrinology (2008), Progress in Neurobiology (2009), Frontiers in Neuroendocrinology (2010), and others. Dr. Tsutsuis h-index is 63. 

Dr. Tsutsui was awarded Zoological Society Prize from the Zoological Society of Japan in 2001, Farner Medal from the International Society for Avian Endocrinology in 2008, Yoshimura Prize from the Japan Society for Pituitary Research in 2008, Bargmann-Scharrer Award from the International Federation of Comparative  Endocrinology Societies (IFCES) in 2013, In Recognition for the Major Contribution from the Society for Research of the Cerebellum (SRC) in 2015, Prize for Science and Technology, The Commendation for Science and Technology from the Minister of Education, Culture, Sports, Science and Technology, Japan in 2015, Okuma Prize for Science and Technology from Waseda University, Japan in 2015, Kobayashi Award from the Japan Society for Comparative Endocrinology in 2016, Top Cited Certification from Journal of Molecular Endocrinology in 2017 and others. 

Dr. Tsutsui has also been giving tremendous services to several Academic Societies. Dr. Tsutsui is currently the President of the International Federation of Comparative Endocrinology Societies, the President of the International Society for Avian Endocrinology, the President Japan Society for Avian Endocrinology and the Representative Member of the International Ornithologists Union. He was the Past-President of the Asia and Oceania Society for Comparative Endocrinology andthe Past-President of the Japan Society for Comparative Endocrinology. Thus, Dr. Tsutsui has been contributing a great deal to the advancement of Neuroendocrinology. 

Neuroendocrinology and reproductive endocrinology