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 IGF-I level in fact represents a relevant measurement when the postexercise proteinuria is under analysis. To verify the IGF-I level variation in the circulation and in urinary excretion in the occasion of a competition, the plasma and urine IGF-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 IGF-I (pIGF, uIGF), total urinary proteins (uPr), and creatinine (uCr) concentrations were measured. RESULTS: The uIGF [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 pIGF was 262.6+/-14.3 and 247.3+/-11.8 microg/l before and end-exercise, respectively. A statistical correlation between uIGF and uPr was demonstrated (p<0.001). The pIGF/uIGF ratio was significantly (p<0.05) decreased comparing the end with before the competition. CONCLUSIONS: The pIGF/uIGF 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.

Growth hormone/insulin-like growth factor 1 axis recovery after liver transplantation: a preliminary prospective study.

Many studies on cirrhotic patients have shown that insulin-like growth factor 1 (IGF-1) plasma levels are related to the severity of liver dysfunction. This result suggests that IGF-1 is probably useful for monitoring liver function in the perioperative course of orthotopic liver transplantation (OLT). Growth hormone (GH), IGF-1 plasma levels, and routine liver function tests were measured in 15 adult cirrhotic patients undergoing OLT. Measurements were made at the beginning of the operation; during OLT; 24 hours after reperfusion; and in the morning on days 7, 30, and 90. Twenty age-matched healthy volunteers with normal liver function served as controls. The study group had significantly higher GH levels and lower IGF-1 levels in the preoperative period compared with the controls. All patients achieved a complete functional hepatic recovery 1 month after OLT, although in 6 of them, the graft had an initial poor function (Group-IPF). GH and IGF-1 levels achieved near normal range within 1 week after OLT, and they had no significant correlations with other routine biochemistry tests in this period. IGF-1 levels in Group-IPF rose more slowly than in the group with a normal recovery of graft function. Surprisingly, 24 hours after reperfusion, IGF-1 levels were higher in Group-IPF than in the group with normal graft function. In conclusion, the severe GH/IGF-1 axis impairment found in patients with end-stage cirrhosis reverted very rapidly in the first days after successful OLT. Such a quick, postoperative modulation of IGF-1 plasma level by the graft suggests that this hormone has the potential to become one of the early indicators of post-OLT liver function recovery.

Effects of acute, heavy-resistance exercise on urinary peptide hormone excretion in humans.

To examine physical exercise-related changes in urinary excretion of protein/peptide hormones and to correlate modifications with the general increase in post-exercise proteinuria, urine C-peptide, insulin and insulin-like growth factor-I (IGF-I) and their plasma concentrations were measured. Plasma and urinary C-peptide, insulin and IGF-I before (Bex) and at the end (Eex) of physical exercise (a 2.5-hour competition, 102 km) were analysed in 20 young cyclists. At Eex compared with Bex, concentration of urinary C-peptide decreased slightly but significantly (21.3 +/- 2.7 vs. 13.5 +/- 1.7 nmol/l), but urinary insulin and urinary IGF-I concentrations significantly increased at Eex (92.5 +/- 4.2 vs. 131.4 +/- 15.7 pmol/l and 10.0 +/- 2.1 vs. 33.6 +/- 3.8 pmol/l, respectively). Plasma insulin and plasma C-peptide significantly decreased, whereas plasma IGF-I was unchanged. Urinary concentrations of total proteins and creatinine significantly increased. Both Eex urinary C-peptide/urinary protein and urinary C-peptide/urinary creatinine ratios were significantly reduced. The correlation between C-peptide and insulin in plasma was confirmed at Bex as well as Eex, but in urine only at Bex. An increased renal tubular reabsorption of C-peptide at the end of exercise might be suggested, but the expected values considering creatinine excretion were almost three times less. The Eex urinary insulin concentration was higher than expected, considering the circulation levels, but lower when compared with the expected concentration considering creatinine excretion. Physical exercise proteinuria, related to an increased protein filtration and a saturation of the mechanisms responsible for the reabsorption, does not appear similar for all peptide hormones.

The measurement of insulin-like growth factor-I (IGF-I) concentration in random urine samples.

The aim of the present study was to assess a suitable expression of the urinary concentration of a protein/ peptide hormone such as insulin-like growth factor-I (IGF-I), measured in the urine of healthy individuals when the specimen collection is executed randomly. One hundred and twenty male subjects were divided by age into four groups, namely healthy sedentary young (SYA) and older (SOA) adults, older (OC) and young (YC) children. In a single urine specimen, randomly collected during the morning from each individual, total urinary IGF-I was measured by immunoradiometric method, and urinary creatinine (uCr) and total proteins (utPr) were measured by capillary electrophoresis and spectrophotometric methods, respectively. The urinary IGF-I concentrations were not significantly different in all groups investigated and they were (mean +/- SD): 82.7 +/- 82.8 ng/l, 103.5 +/- 83.3 ng/l, 80.4 +/- 64.4 ng/l in OC, SYA and SOA, respectively; only in the YC group there was a tendency to higher values (125.2 +/- 93.2 ng/l) compared with the other groups. utPr ranged from 26 to 40 mg/l and did not demonstrate significant differences between groups. The urinary IGF-I correlated with uCr and utPr, and statistical significance was observed in all measurements. The measurement of urinary IGF-I in random urine and its ratio to utPr is an innovative, useful way of investigation of urinary protein/peptide hormones.

Urinary insulin-like growth factor I in athletes, before and after physical exercise, and in sedentary subjects.

BACKGROUND: Insulin-like growth factor I (IGF-I), like growth hormone (GH), is excreted in urine in a smaller fraction than the concentration found in blood. Exercising subjects undergo post-exercise proteinuria. The present work aims to propose a method for urinary IGF-I analysis (uIGF-I) by defining urinary concentration in sedentary individuals and athletes before and after strenuous exercise. METHODS: Urine samples were collected from 30 sedentary healthy male individuals during the morning and from 30 well-trained cyclists, before and after a competition of about 3 h (150 km). uIGF-I was measured in undiluted acidified urine by radioimmunoassay (RIA) method using a purified polyclonal rabbit antibody, human 125I-IGF-I and a second anti-rabbit antiserum. The acidification of the urine samples and the excess of IGF-II addition in the incubation medium of the assay were used to dissociate the binding and to block the interference from IGF binding proteins (IGFBPs). Urinary growth hormone (uGH), total protein (utPr) and creatinine (ucr) concentrations were also measured by immunoradiometric assay (IRMA), colorimetric and capillary electrophoresis methods, respectively. RESULTS: The analysis range was 0-2500 ng/l (0-327 pmol/l), the intra- and inter-assay coefficients of variations (CVs) ranged from 2.3% to 7.8%, respectively. The detection limit was 0.6 pg/tube. The uIGF-I/creatinine (cr) ratio in healthy subjects was 70 +/- 8 pg/mg cr. The uIGF-I/creatinine ratio (pg/mg cr) was different (p<0.001) in athletes before vs. after competition 93 +/- 27 vs. 136 +/- 13. Athletes' [uIGF-I/total proteins] ratio (ng/mg tPr) before and post-exercise was 2.3 +/- 0.5 and 2.5 +/- 0.3, respectively. CONCLUSIONS: uIGF-I assay appears to be an effective way of monitoring IGF-I excretion. In the cyclists, in the pre-exercise state, uIGF-I was comparable with that measured in sedentary healthy individuals. In the cyclists, after strenuous exercise, the increased uIGF-I/cr and uGH/cr ratios suggested a relation with the post-exercise proteinuria. In conclusion, proteinuria physiologically obtained, such as post-exercise proteinuria, might be a new approach in IGF-I system investigation.