ATPおよびdibutyryl cAMPの投与によりα-hANP分泌不全の改善が認められた粘液水腫心の1例

A case of myxedema heart showing the improvement of impaired α-hANP secretion by administration of ATP and dibutyryl cAMP

　症例は40歳の女性で全身倦怠感，労作時の呼吸困難を初発症状として入院した。び漫性の甲状腺腫，非陥凹性の下腿浮腫を認めた。主要検査成績では，血清T₄，T₃の低下，血清TSHの著明な増加，thyroid test，microsome testはともに陽性を示した。心電図は全誘導でQRS波の低電位，断層心エコー図は著明な心膜液の貯留を示した。以上の所見より，本例は慢性甲状腺炎による粘液水腫心と考えられた。右房ペーシング後の平均右房圧は正常対照に比べ上昇したが，血漿hANP濃度は正常対照ほどは増加しなかった。右房ペーシング後の血漿hANP濃度は，甲状腺機能の正常状態の時が甲状腺機能低下状態に比べより増加した。右房ペーシングにATPまたはdb-cAMPを加えると，これらの薬剤を加えないときに比べ，血漿hANP濃度は高値を示した。粘液水腫心の1例にα-hANPの分泌不全を見い出し，甲状腺ホルモン，ATP，db-cAMPの投与により，その分泌能が改善することを示した。

A 40-year old female was admitted with com-plaints of general fatigue and dyspnoea brought on by effort. There were edema on the face, a diffuse and slightly hard goiter on the neck and non-pitting edema in the lower legs. Laboratory findings showed low levels of serum T₃ (0.37ng/ml) and T₄ (2.0μg/dl), a very high level of serum TSH (549.8μU/l), positive thyroid test (×400) and positive microsome test (×102,400). The chest roentgenogram showed an enlargement (CTR 62%) of the cardiac silhouette in the shape an ice bag, and the electrocardiogram revealed low QRS voltage with T-wave flattening in all leads. Remar-kable pericardial effusion was shown on the two-dimensional echocardiogram. Judging from the indications of hypothyroidism, positive antithyroid antibody and pericardial effusion. This patient was diagnosed as having myxedema heart due to chronic thyroiditis.

The levels of plasma α-hANP did not elevate so much as the levels in normal controls after right atrial (RA) pacing, although mean right atrial pressure was higher than in normal controls after RA pacing. The levels of plasma α-hANP after RA pacing in euthyroid state were higher than those in hypothyroid state. The levels of plasma α-hANP after RA pacing became higher after the administration of ATP or db-cAMP both in euthy-roid and hypothyroid states.

These results indicate that the impaired α-hANP secretion in myxedema heart is improved by the administration of thyroxine, ATP or db-cAMP.