Effect of dexamethasone on growth hormone (GH) response to growth hormone releasing hormone in acromegaly.
The effect of dexamethasone on the GH response to GH-releasing hormone (GHRH) was studied in vivo in six patients with acromegaly as well as in vitro in monolayer cultures of GH-secreting pituitary tumor cells obtained from three of these patients. Oral administration of 9 mg/day dexamethasone for 2 days decreased plasma GH responses to iv injection of 100 micrograms GHRH-(1-44 amide) in all six patients. Blood glucose levels were significantly increased, while plasma somatomedin-C levels were significantly decreased by this regimen of dexamethasone treatment. On the other hand, 2-day pretreatment with 50 nM dexamethasone of monolayer cultures of pituitary adenoma cells potentiated GH release basally and/or in response to 100 pM to 1 nM GHRH in vitro. These results indicate that the potentiating action of 2-day treatment of dexamethasone in vitro is overwhelmed in vivo by some extra-pituitary action, probably on the central nervous system, of glucocorticoids in patients with acromegaly.
D000172:Acromegaly / Q000097:blood*; D000236:Adenoma / Q000378:metabolism; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007334:Insulin-Like Growth Factor I; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000378:metabolism; D013002:Somatomedins / Q000097:blood
D001786:Blood Glucose; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D003907:Dexamethasone; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone