PURPOSE: The acromegalic state is associated with an increase in total body water and sodium. The aim of our study was to assess the hydration status of patients with acromegaly using bioimpedance vector analysis (BIVA), differentiating patients according to their disease status (active, medically controlled or cured) and to compare the confidence and tolerance ellipses of BIVA in those patients in relation to a reference healthy population. METHODS: We analyzed data from 73 consecutive patients aged 18 years or older, diagnosed with acromegaly and undergoing regular follow-up at our Division for whom a BIVA analysis was available. Patients were evaluated through BIVA and insulin-like growth factor I (IGF-I), growth hormone (GH), serum sodium and potassium, creatinine, glucose, HbA1c and plasma and urine osmolality were collected. Exclusion criteria were concurrent presence of arginine-vasopressin deficiency, dysnatremia or the presence of pathologies known to significantly alter the extracellular fluid. RESULTS: Sixty-nine patients (M/F 34/35, age 60 ± 14 years) were enrolled in the study. As expected, patients with active disease (n = 22) presented higher IGF-I and GH levels compared to other subjects. Patients with controlled disease (n = 33) were significantly older than other individuals (p = 0.028 vs. active disease, p = 0.024 vs. cured disease). Compared to a reference healthy population, patients with either active or medically controlled disease showed significant fluid overload (p <
0.0001 for both males and females) and BIVA confidence analysis demonstrated that there were no significant differences in hydration status between the two groups (p = 0.363). On the other hand, patients with cured disease (n = 14) showed reduced hydration status compared to patients with active disease (p = 0.016), although no difference was observed compared to patients with controlled disease (p = 0.308). CONCLUSION: The results of our study demonstrate that patients with either active or medically controlled acromegaly present a significant overhydration compared to a healthy reference population and that alterations in body water content usually improve in individuals with cured disease.