Elevated circulating somatostatin levels in acromegaly

GH increases hypothalamic somatostatin (SS) synthesis and secretion but it is unknown if chronic GH excess, as found in acromegaly, may influence circulating SS levels, that are mainly of enteropancreatic source and affect several gastrointestinal functions, including motility. Circulating SS occurs in several post-translational forms including somatostatin-14 (SS-14), somatostatin-28 (SS-28) and other small peptides. The aim of the present study was to characterize the fasting and postprandial pattern of plasma circulating somatostatin in normal subjects and patients with acromegaly. Fasting total SS and SS-28 levels were measured in 32 subjects, 16 acromegalic patients with a new diagnosis (A) (8 F, 8 M, median age 48) and 16 matched healthy volunteers (C) (8 F, 8 M, median age 45). SS was also determined after a standard solid-liquid meal (550 kCal) in 24 of the subjects (12 C and 12 A). Fasting SS and SS-28 were significantly higher in acromegalic patients as compared to healthy subjects. In the former, a positive correlation was found between IGF-I and SS levels (r=0.525 p