Orthopedia (Otp) transcription factor is a critical determinant in the development of the neuroendocrine hypothalamus, and its embryonic deletion results in lethality. Although Otp expression is maintained throughout life, its physiological function in adulthood is not well understood. Here, we generated a forebrain-specific, tamoxifen-inducible, conditional knockout mouse model to investigate the roles of Otp beyond development. Conditional deletion of Otp in two-month-old mice resulted in impa