The effects of ghrelin on GH, ACTH and cortisol release in thyrotoxicosis

Abstract

In thyrotoxicosis there is an impaired GH response to several stimuli. Ghrelin is a potent GH secretagogue and it also induces ACTH and cortisol release in men. We evaluated the effects of ghrelin in 6 hyperthyroid patients and in 8 controls. In thyrotoxicosis peak GH (mu g/L; mean +/- SE) levels after ghrelin administration were significantly lower than those observed in controls (20.9 +/- 3.5 vs. 62.6 +/- 10.3). The same pattern was seen with AUC (mu g/L.120min) values (871 +/- 141 vs. 3667 +/- 662). ACTH and cortisol levels after ghrelin injection were similar in thyrotoxic patients and controls. In summary, our data shows that ghrelin-induced GH release is decreased in thyrotoxicosis, while ACTH and cortisol responsiveness is maintained. This could suggest that thyroid hormone excess interferes with GH releasing pathways activated by ghrelin.