The present invention provides a variety of useful polypeptides. In particular, a polypeptide comprising the same or substantially the same amino acid sequence as the amino acid sequence represented by SEQ ID NO: 1, SEQ ID NO: 2 or SEQ ID NO: 3, its amide, or a salt thereof can be used as an agent for preventing/treating hypotension; an agent for preventing/treating obesity, hyperphagia, etc.; an agent for preventing/treating lethargy, time-zone change syndrome (jet lag), etc.; an agent for preventing/treating sterility, etc. A compound or its salt that promotes the activity of a polypeptide comprising the same or substantially the same amino acid sequence as the amino acid sequence represented by any of SEQ ID NOS: 7 to 12 and 37 to 42, its partial peptide, or a salt thereof is useful as an agent for preventing/treating, e.g., menopausal symptoms or hyperthyroidism. A compound or its salt that inhibits the activity of said polypeptide is useful as an agent for preventing/treating, e.g., sterility or hypothyroidism.