Abstract
Low GH response to provocative stimuli in CD is a well established phenomenon. However most of the stimuli used act through release of endogenous GRF and it is not known whether hypercortisolaemia interferes with hypothalamic GRF generation, or GRF action upon somatotrophs, or both. To investigate pituitary GRF responsiveness in hypercortisolaemia we used GRF-44 (Sanofi) as a i.v. bolus (2 μg/kg) in two patients with pituitary dependent CD. Patient AP was a 13½ yr old girl with intermediate lobe type CD present for 6 yr but recognized and treated by bromocriptine for the last two yr. One month after therapy was stopped her midnight F was 17.9 μg/dl; the peak serum GH response to GRF was 3.6 ng/ml and to oral clonidine 0.8 ng/ml. After one month's bromocriptine treatment the midnight serum F concentration decreased to 1.3 μg/dl. Peak GH response to GRF and clonidine at that time were 14.9 and 4.7 ng/ml. Patient AK a 10½ yr old boy with a 4 yr history of anterior lobe CD and midnight serum F level of 33.5 μg/dl, responded to GRF and clonidine tests with GH peak values of 1.0 ng/ml and 0.6 ng/ml respectively. In patient AK the midnight serum F was 39.3 μg/dl after 1 month's of bromocriptine treatment. The GH response to GRF and clonidine were 1.0 ng/ml and 2.6 ng/ml respectively. We conclude that hypercortisolaemia in patients with CD interferes with pituitary responsiveness to GRF; in vitro studies by others suggested this is not a direct effect on the somatotrophs.
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