Effects of two different types of exercise on GH/IGF axis in athletes. Is the free/total IGF-I ratio a new investigative approach?
BACKGROUND
Human growth hormone (hGH) responds to bouts of exercise by increasing, while the insulin-like growth factor-I (IGF-I) responses are conflicting.


METHODS
Twenty well-trained male cyclists completed a brief duration exercise (A: warm up+increasing workload until exhaustion, lasting 25 min) and a medium duration exercise (B: warm up+70-80%VO(2 max)+increasing workload until exhaustion, lasting 40 min). The immunoreactivity of plasma hGH, the IGF-I in its total and free fraction were measured before and at the end of the exercise, and the free/total IGF-I ratio response to the two cycling exercise bouts was examined.


RESULTS
Both A and B demonstrated increased hGH (from 77+/-122 to 544+/-327 and 28+/-68 to 369+/-276 pmol/l respectively) and total IGF-I (from 67+/-10 to 70+/-10 and 55+/-14 to 61+/-15 nmol/l respectively). The free IGF-I was decreased only in A (from 0.38+/-0.16 to 0.32+/-0.14 nmol/l). Both A and B demonstrated a decreased free/total IGF-I ratio (from 0.57+/-0.30 to 0.46+/-0.22 and 0.61+/-0.37 to 0.52+/-0.29).


CONCLUSIONS
Brief and medium duration physical exercise influences the hGH, the total and free IGF-I concentrations. The free/total IGF-I ratio was also influenced and it might be related to the GH/IGF system. Its investigation might be a way of studying the training condition.
De Palo
Elio F
EF
Section of Clinical Biochemistry, Department of Medical Diagnostic Sciences and Sp.Ther., University of Padua, Padua, Italy. eliof.depalo@unipd.it
Antonelli
Giorgia
G
Gatti
Rosalba
R
Chiappin
Silvia
S
Spinella
Paolo
P
Cappellin
Enrico
E
D004797:Enzyme-Linked Immunosorbent Assay; D015444:Exercise; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length
D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone