Ghrelin Secretion in Humans Is Sexually Dimorphic, Suppressed by Somatostatin, and Not Affected by the Ambient Growth Hormone Levels

Abstract

We studied plasma ghrelin and GH concentrations over a 24-h period in young healthy men and women and in patients with acromegaly. Healthy subjects were restudied after administration of GH-lowering agents, octreotide or GHRH antagonist. Ghrelin concentrations in women studied during the late follicular stage of the cycle were about 3-fold higher than in men. Suppression of GH secretion by GHRH antagonist did not alter ghrelin concentration profiles. In the presence of high GH levels (acromegaly), ghrelin levels were similar to those found in healthy men. Administration of somatostatin analog octreotide suppressed both GH and ghrelin concentration profiles. We conclude that: 1) ghrelin secretion is sexually dimorphic in humans, with women in the late follicular stage having higher levels than men; 2) ghrelin secretion is suppressed by somatostatin; and 3) GH has no influence over ghrelin secretion.