Endocrine Abstracts

JOINT436

Background: Emerging research suggests that tissue Na⁺ accumulation plays a role in blood pressure control, yet the mechanisms underlying the regulation of sodium storage remain unclear to date.

Methods: In 31 hypertensive patients with a mean age of 49 years, of whom 61% were women, a sodium infusion test (SIT) was conducted to confirm or exclude the diagnosis of primary aldosteronism (PA). For this purpose, 2000 ml of isotonic saline were intravenously infused over 4 hours. Both before and immediately after the sodium infusion, each patient underwent sodium magnetic resonance imaging (²³NA-MRI), a specialized noninvasive imaging technique that focuses on visualizing the distribution and concentration of sodium ions within tissues.

Results: The mean sodium content in skin and muscle tissue in the study cohort was 45±3.4 mmol/l and 17.9±2.8 mmol/l, respectively, prior to the intervention. Following salt loading, in both compartments a significant increase in salt accumulation (+18%, P<0.001; +4.4%, P=0.004) could be observed. Based on the SIT, PA was diagnosed in 17 cases (54.8%) and excluded in four cases (12.9%), while remaining inconclusive in ten cases (32.3%). Across diagnostic categories, the aldosterone-to-renin ratio (ARR) correlated positively with the level of baseline salt content in the skin (P=0.03). While a similar trend was evident in muscle tissue, it did not reach statistical significance. Muscle salt accumulation was significantly less pronounced in patients with a post-SIT aldosterone level above the median of 135 ng/l compared to those with lower aldosterone values (Δ1.48% versus Δ7.23%, P=0.016).

Conclusions: This study demonstrates a significant increase in sodium accumulation within skin and muscle tissues among hypertensive individuals following short-term sodium loading. In addition, we demonstrate a positive correlation between ARR and sodium stores in the skin prior to intervention. In muscle tissue, we observe a negative correlation between post-SIT aldosterone levels and the percentage of sodium accumulation. The data may provide an indication of a potential influence of aldosterone on sodium dynamics within body tissues. Increasing patient numbers and further investigation is required to assess whether differences in tissue sodium distribution before and after loading could serve as a discriminating factor between endocrine forms of hypertension and essential hypertension.