ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2006) 12 P79

Combining GHRH/Arginine with a synacthen test diminishes the cortisol response

S Siyambalapitiya2, DUS Bulugahapitiya2, V Ibbotson2, A Doane2, E Ghigo1, MJ Campbell2 & RJ Ross2


1University of Turin, Turin, Italy; 2University of Sheffield, Sheffield, United Kingdom.


Rationale, aims and objectives

The GHRH/Arginine and Short Synacthen Tests (SST) have been validated as safer alternatives to the Insulin Tolerance Test for the assessment of the growth hormone reserve and Hypothalamic-Pituitary-Adrenal axis integrity, respectively. However, these two tests are performed separately. The objective of this study was to see whether the synacthen and GHRH/Arginine tests could be combined to save time, blood samples and minimize inconvenience to the patients.

Method

The study was approved by the Ethics committee and patients gave written informed consent. 24 consecutive patients with adult onset pituitary disease who required anterior pituitary function testing were randomized to receive sequentially and in random order a Synacthen test, a GHRH/Arginine test and a combined Synacthen and GHRH/Arginine test. Patients underwent the three different tests on three different visits separated by at least a week.

Results

There was no difference in basal cortisol or ACTH values for the synacthen test done alone or during the combined test. However when GHRH/Arginine was given with synacthen, patients had a significantly lower peak cortisol response (P<0.001) with a clinically significant outcome difference. The difference between the peak responses showed no correlation with age (R=0.123, P=0.577). However, there was a significant negative correlation with the Body Mass Index (R=−0.376, P=0.093). There was no difference between the GH measurements at any time point or the peak value between the GHRH/Arginine test alone or when combined.

Conclusions

Combining the SST and GHRH/Arginine test results in a lower cortisol response to synacthen. For this reason, the combined test cannot be recommended to assess the integrity of cortisol and GH reserve.

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