[A case of myxedema heart showing the improvement of impaired alpha-hANP secretion by administration of ATP and dibutyryl cAMP].

A 40-year old female was admitted with complaints 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 (0.37 ng/ml) and T4 (2.0 micrograms/dl), a very high level of serum TSH (549.8 microU/l), positive thyroid test (x 400) and positive microsome test (x 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. Remarkable 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 alpha-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 alpha-hANP after RA pacing in euthyroid state were higher than those in hypothyroid state. The levels of plasma alpha-hANP after RA pacing became higher after the administration of ATP or db-cAMP both in euthyroid and hypothyroid states. These results indicate that the impaired alpha-hANP secretion in myxedema heart is improved by the administration of thyroxine, ATP or db-cAMP.