The effect of short-term cortisol changes on growth hormone responses to the pyridostigmine-growth-hormone-releasing-hormone test in healthy adults and patients with suspected growth hormone deficiency

BACKGROUND AND AIMS The interaction between cortisol and growth hormone (GH)-levels may significantly influence GH-responses to a stimulation test. In order to systematically analyse the interaction in a paired design, it is necessary to use a test, which has been proven safe and reliable such as the pyridostigmine-growth-hormone-releasing-hormone (PD-GHRH) test, Three groups of subjects with a different GH-secretory capacity were included, STUDY A Eight healthy adults were tested seven times, once with placebo throughout the examination and six times with the PD-GHRH test following no glucocorticoid pretreatment, pretreatment with hydrocortisone (HC) (30 mg/day and 80 mg/day for 1 and 3 days) or pretreatment with 15 mg prednisolone for 1 day. HC (80 mg/day for 1 day) in combination with PD significantly stimulated GH-levels compared to PD alone, 18.9 mU/l +/- 6.1 vs 3.0 mU/l +/- 0.8 (P< 0.05). However, peak GH-responses to PC in combination with GHRH were reduced during HC (80 mg/day for 1 day) compared to no glucocorticoid pretreatment in all healthy adults. Conventional HC therapy (30 mg/day for 1 and 3 days) did not significantly affect peak GH-responses, STUDY B 16 patients with suspected GH-deficiency (GHD) (seven with known ACTH-deficiency and nine with an intact pituitary-adrenal axis) were tested five times with the PD-GHRH test following no pretreatment or pretreatment with HC (30 mg/day and 80 mg/day for 1 and 3 days), Peak GH-responses were not significantly affected by conventional HC therapy (30 mg/day for 1 and 3 days). However, peak GH-responses to PO in combination with GHRH were reduced during HC (80 mg/day for 1 day) compared to no glucocorticoid pretreatment in all patients, Short-term hypocortisolism did not significantly affect peak GH-responses, CONCLUSION The GH-responses to a PD-GHRH test were reduced in all individuals during acute stress-appropriate cortisol levels and the percentage reduction in GH-levels was independent of the GH-secretory capacity, Clinically, we found that peak GH-responses were not significantly affected by a short break in conventional HC therapy nor by conventional HC therapy itself. However, our results also demonstrated that a GH-stimulation test should not be performed on patients, suffering from acute stress.