A macrocyclic polypeptide represented by formula or a pharmacologically acceptable salt thereof, wherein X aa1 is a residue of Arg, Lys, His, Gly, Ala, Asn, Thr, Ser, Met, Leu, Ile, Val, Gln, Phe, Tyr, Trp, or Cys, or is absent; X aa2 is a residue of Phe, Tyr, Trp, 2Nal, 4CF, or DCF; X aa3 is a residue of Ile, Leu, Nle, Tle, Trp, 2Nal, 4CF, or Arg; X aa4 is a residue of Ser; X aa5 is a residue of Gly; X aa6 is a residue of Arg, Lys, His, Ser, Cit, or MO2; X aa7 is a residue of Asn or Asp; X aa8 is a residue of Trp, 2Nal, or 6CW; X aa9 is a residue of Val, Nle, Ahp, or Met; X aa10 is a residue of Arg, Lys, His, AMF, Phg, or Val; X aa11 is a residue of Trp or 2Nal; X aa12 is a residue of Val, Tle, or Phe; wherein 2Nal represents, 4CF represents DCF represents Nle represents Tle represents Cit represents MO2 represents 6CW represents Ahp represents AMF represents Phg represents A is a linking group of the formula: wherein represents a point of attachment to the N-terminal amino group of X aa1, or in the absence of X aa1, represents a point of attachment to the N-terminal amino group of X aa2, represents a point of attachment to the C-terminal carbonyl group of X aa12. or a pharmacologically acceptable salt thereof, wherein X aa1 is a residue of Arg, Lys, His, Gly, Ala, Asn, Thr, Ser, Met, Leu, Ile, Val, Gln, Phe, Tyr, Trp, or Cys, or is absent; X aa2 is a residue of Phe, Tyr, Trp, 2Nal, 4CF, or DCF; X aa3 is a residue of Ile, Leu, Nle, Tle, Trp, 2Nal, 4CF, or Arg; X aa4 is a residue of Ser; X aa5 is a residue of Gly; X aa6 is a residue of Arg, Lys, His, Ser, Cit, or MO2; X aa7 is a residue of Asn or Asp; X aa8 is a residue of Trp, 2Nal, or 6CW; X aa9 is a residue of Val, Nle, Ahp, or Met; X aa10 is a residue of Arg, Lys, His, AMF, Phg, or Val; X aa11 is a residue of Trp or 2Nal; X aa12 is a residue of Val, Tle, or Phe; wherein 2Nal represents, 4CF represents DCF represents Nle represents Tle represents Cit represents MO2 represents 6CW represents Ahp represents AMF represents Phg represents A is a linking group of the formula: wherein represents a point of attachment to the N-terminal amino group of X aa1, or in the absence of X aa1, represents a point of attachment to the N-terminal amino group of X aa2, represents a point of attachment to the C-terminal carbonyl group of X aa12. X aa2 is a residue of Phe, Tyr, Trp, 2Nal, 4CF, or DCF; X aa3 is a residue of Ile, Leu, Nle, Tle, Trp, 2Nal, 4CF, or Arg; X aa4 is a residue of Ser; X aa5 is a residue of Gly; X aa6 is a residue of Arg, Lys, His, Ser, Cit, or MO2; X aa7 is a residue of Asn or Asp; X aa8 is a residue of Trp, 2Nal, or 6CW; X aa9 is a residue of Val, Nle, Ahp, or Met; X aa10 is a residue of Arg, Lys, His, AMF, Phg, or Val; X aa11 is a residue of Trp or 2Nal; X aa12 is a residue of Val, Tle, or Phe; wherein 2Nal represents, 4CF represents DCF represents Nle represents Tle represents Cit represents MO2 represents 6CW represents Ahp represents AMF represents Phg represents 2Nal represents, 4CF represents DCF represents Nle represents Tle represents Cit represents MO2 represents 6CW represents Ahp represents AMF represents Phg represents A is a linking group of the formula: wherein represents a point of attachment to the N-terminal amino group of X aa1, or in the absence of X aa1, represents a point of attachment to the N-terminal amino group of X aa2, represents a point of attachment to the C-terminal carbonyl group of X aa12.