Urinary insulin-like growth factor-I measurement in an actual sport competition, an additional approach in laboratory antidoping tests

Background: The insulin-like growth factor hormone (IGF-I) is an important protein hormone under investigation with physical exercise and for doping detection. Urinary lGF-I level in fact represents a relevant measurement when the postexercise proteinuria is under analysis. To verify the lGF-I level variation in the circulation and in urinary excretion in the occasion of a competition, the plasma and urine lGF-I in athletes before and after an actual competitive event were measured. Methods: Twenty well-trained cyclists took part in a competition (102 km) and concluded the intense physical exercise in approximately 2(1/2) h. Urine and blood samples were collected from each athlete 10-20 min before and at the end of the competition. Plasma and urine total lGF-I (plGF, ulGF), total urinary proteins (uPr), and creatinine (uCr) concentrations were measured. Results: The ulGF [from 76.2 +/- 15.8 to 256.9 +/- 29.1 ng/l (p<0.001)], uPr [from 29.4 +/- 6.7 to 325.9 +/- 95.1 mg/l (p<0.005)], and uCr [from 6.3 +/- 1.0 to 10.0 +/- 0.8 mmol/l (p<0.005)] significantly increased. The plGF was 262.6 +/- 14.3 and 247.3 +/- 11.8 mug/l before and end-exercise, respectively. A statistical correlation between ulGF and uPr was demonstrated (p<0.001). The pIGF/ ulGF ratio was significantly (p<0.05) decreased comparing the end with before the competition. Conclusions: The pIGF/ulGF significantly decreased at the end, compared with before the competition, suggesting a changed uIGF excretion. This increment appeared to be increased, although not significantly, considering the ratio with uCr. (C) 2004 Elsevier B.V. All rights reserved.