GHRH and Cushing syndrome: In addition, specific tests are performed when symptoms suggest hormonal secretion, including urinary dU-5-hydroxy indol-acetic acid in patients with carcinoid syndrome, serum cortisol, 24-hour urine-free cortisol, GHRH, and insulin growth factor (IGF)-I when signs of acromegaly are present and ACTH levels in patients with Cushing syndrome [10].