Endocrine Abstracts

Objective: To evaluate the association between body-composition and peak GH, during two standard GH stimulation tests; the pyridostigmine-GHRH (PDGHRH) test and an insulin tolerance test (ITT).

Method: 83 healthy subjects (56 men), aged 18–65 years with a median BMI of 24 kg/m² (range 17–35) underwent a PDGHRH test and an ITT in random order 1 week to 1 month apart. Women had both tests performed in the same phase of their menstrual cycle. Body composition was assessed by BMI, waist circumference, waist-to-hip (W/H) ratio, total fat percent (TF%) and total (TFM) and abdominal fat mass (abdFM) assessed by dual energy X-ray absorptiometry.

Results: Peak GH was significantly higher in response to PDGHRH stimulation compared to the ITT (mean 73.8 mU/l versus 42.1 mU/l; P< 0.0001). Men and women had similar peak GH values during both tests (P>0.5). In men peak GH in response to the PDGHRH test was negatively correlated to BMI (r=− 0.64), waist (r=− 0.62), W/H (r=− 0.59), TF% (r=− 0.69), TFM (r=− 0.69) and abdominal fat mass (r=− 0.68) (all P<0.0001). In women similar associations were present for BMI (r=− 0.69), TFM (r=− 0.70) and abdFM (r=− 0.71).

Neither men nor women demonstrated significant correlations between peak GH in response to the ITT and body-composition measures.

Conclusion: Body composition had a more prominent inhibitory effect on the results of the PDGHRH test as compared to the ITT in healthy individuals. No gender differences were observed. Measures of central adiposity were not superior to BMI in predicting peak GH in response to the PDGHRH test in healthy individuals. The GH response by ITT seems more resistant to influence from adiposity.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.