Endocrine Abstracts

Inroduction
Due to persistent qualitative abnormalities in GH secretion following treatment, it is extremely difficult to diagnose GHD in treated acromegalic patients. We aimed to study the response of successfully treated acromegalic patients to the combined growth hormone releasing hormone and arginine test and compare it with the insulin tolerance test.
Patients and Methods
Twelve acromegalic patients, in whom mean serum GH level off medical treatment was below 5mU/L were recruited. Six of the patients had been treated by surgery alone and 6 had received primary or postoperative irradiation. The patients attended the day unit after overnight fasting on two days, one week apart. On the first visit day, an insulin tolerance test was performed. On the second visit day, GHRH 1microgramperbody weight (maximum 100microgram)was administered followed by arginine infusion [0.5 gramperkilogram body weight (maximum 35gram) arginine] over 30 minutes.
Results
The mean plus/minus sem for Gh in the group who had only undergone surgery alone or combined with radiotherapy were not significantly different (14.92 +/- 8.27 mU/l for the ITT v 28.55+/-11.65 mU/L for the GHRH+ARG, p=0.07; 0.50 +/-0.16 mU/L for ITT v 8.48+/-6.38 mU/L p= 0.06 respectively). There was good correlation between the delta GH in both tests. A higher peak GH was achieved with the GHRH+ARGININE test compared to the ITT. 80% of patients who had a peak GH less than 10 mU/l on ITT also had a peak GH less than 10 mU/L on the GHRH+Arginine test. Patients experienced fewer side effects with the combined test.
Conclusion
The combined GHRH+Arginine test is a reliable alternative to the ITT in the diagnosis of growth hormone deficiency following successful treatment of acromegaly. However this needs to be confirmed in larger series. Growth hormone deficiency is more common after radiotherapy.