Abstract
We reported previously that a high level of plasma antidiuretic hormone (ADH) was frequently observed in patients with endolymphatic hydrops. However, the reason for this elevation in plasma ADH level remains unclear. The secretion of ADH is known to be controlled mainly by plasma osmolality. We investigated the correlation between the plasma ADH level and plasma osmolality in 106 patients with and in 59 without endolymphatic hydrops. The mean plasma ADH level was 6.8±4.1pg/ml in the patients with endolymphatic hydrops, significantly higher than the 3.2±2.0pg/ml level in those without endolymphatic hydrops (t-test, p<0.001); but there was no significant difference in plasma osmolality between the two groups, in both of which it was in the normal range. Thus, the markedly elevated plasma ADH level found in patients with endolymphatic hydrops seems to be independent of plasma osmolality.
