Changes in the plasma and urine alpha human atrial natriuretic peptide (alpha hANP) concentration in patients with thyroid disorders.

In order to assess the possible involvement of thyroid hormone in alpha human atrial natriuretic peptide (alpha hANP), we investigated the plasma and urine ANP concentration in patients with primary hyperthyroidism and hypothyroidism. Plasma and urine were extracted through Sep-Pak C18 cartridges and the urine ANP concentration was corrected by urine creatinine (cre. mg/dl) and expressed as fmol/mg.cre.. The plasma ANP concentration in patients with untreated hyperthyroidism (32.3 +/- 7.0 fmol/ml; n = 22) was higher than in normal subjects (p less than 0.01 vs control; 6.2 +/- 0.7 fmol/ml). After restoration to euthyroidism, the plasma ANP concentration (patients with treated hyperthyroidism) fell to normal (8.9 +/- 1.9 fmol/ml). The plasma ANP concentration in patients with untreated hypothyroidism (14.1 +/- 3.0 fmol/ml; n = 7) was higher than normal, but in two of them there was mild renal dysfunction and an incomplete right blundle branch block in the electrocardiogram. It was possible that these factors contributed to the observed increase in plasma ANP. However, a significant positive correlation was found between plasma ANP and free thyroxine (n = 40, r = 0.449; p less than 0.01) and free triiodothyronine (n = 40, r = 0.546; p less than 0.01). The urine ANP concentration in patients with untreated hyperthyroidism was markedly higher than in normal subjects (p less than 0.01), but in untreated hypothyroidism not significantly different from normal.