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Applied Physiology Research Laboratory, Kent State University, Kent, Ohio 44242
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
ACKNOWLEDGEMENTS
FOOTNOTES
REFERENCES
ABSTRACT 
Roemmich, James N., and Wayne E. Sinning. Weight loss
and wrestling training: effects on growth-related hormones.
J. Appl. Physiol. 82(6):
1760-1764, 1997.
Adolescent wrestlers
(n = 9, 15.4 yr) and recreationally
active control males (n = 7, 15.7 yr)
were measured before, at the end of, and 3.5-4 mo after a
competitive wrestling season to assess the influence of dietary restriction on growth-related hormones. Wrestlers had significant elevations preseason to late season for morning serum concentrations (mean of 8 serial samples) of growth hormone (GH; 2.9 ± 0.7 vs. 6.5 ± 1.4 ng/ml) and sex hormone-binding globulin (SHBG; 16.1 ± 2.3 vs. 27.9 ± 6.9 nmol/l) and significant reductions in GH-binding protein (GHBP; 178 ± 19 vs. 109 ± 17 pmol/l), insulin-like
growth factor I (IGF-I; 332 ± 30 vs. 267 ± 34 ng/ml),
testosterone (T; 4.9 ± 0.4 vs. 3.6 ± 0.4 ng/ml), and free
testosterone (Free-T; 22.4 ± 3.6 vs. 15.7 ± 2.8 pg/ml).
Wrestlers had significant postseason reductions in GH (3.44 ± 1.30 ng/ml) and SHBG (10.43 ± 4.13 nmol/l) but elevations
in GHBP (66.7 ± 23.8 pmol/l), IGF-I (72.9 ± 25.1 ng/ml),
T (2.10 ± 0.46 ng/ml), and Free-T (9.76 ± 3.01 pg/ml). Concentrations of luteinizing hormone (LH), estradiol,
prolactin, cortisol, insulin, and thyroid hormones did not differ
because of exercise-dietary practices of wrestlers. In-season
elevations in GH, with concomitant reductions in GHBP and IGF-I, that
were reversed during the postseason suggest a reduction in GH receptor number and partial GH resistance during the season. Nonelevated LH with
reduced T levels suggests a central hypothalamic-pituitary-gonadal (H-P-G) axis impairment. In conclusion, undernutrition may lead to
altered H-P-G and GH-IGF-I axes function in adolescent wrestlers. However, only the wrestlers' late-season Free-T concentrations were
outside the normal range, and the hormone axis impairments were quickly
reversed. The present data do not address hormonal axis responses to
several years of wrestling and weight loss.
growth hormone; growth hormone-binding protein; insulin-like growth
factor; insulin-like growth factor-binding protein 3; testosterone
INTRODUCTION DESPITE CAUTIONS from the medical community (1),
adolescent wrestlers continue to reduce their body weight through a
combination of dietary restriction and exercise to prepare for athletic
competition (27). Repetitive weight loss each week over a 3- to 4-mo
wrestling season is associated with chronic weight loss and
undernutrition (10, 23, 24).
The undernutrition of adolescent wrestlers has led several
investigators to suggest that weight-loss practices of wrestlers may
lead to temporary growth suppression (18, 31). Previous studies of
pubescent wrestlers have shown that some markers of somatic growth
indicate decreased incremental growth during the season and increased
incremental (catch-up) growth postseason (23, 24). Others have shown
that during the sport season, collegiate (postpubertal) wrestlers have
reductions in growth-related hormone concentrations (7, 18, 28). In a
companion paper (24), we sought to verify whether the nutritional
status of adolescent wrestlers is compromised and whether
undernutrition slowed their growth and maturation. Here we discuss the
alterations in growth-related hormones of undernourished adolescent
wrestlers.
METHODS
,5-triiodo-L-thyronine (T3), insulin, GH-binding
protein (GHBP), IGF-binding protein 3 (IGFBP3), sex hormone-binding
globulin (SHBG), and alkaline phosphatase. The catheter was then
removed. After clotting occurred, the blood samples were centrifuged,
and the serum samples were partitioned before freezing at
135°C. Serum samples were divided into aliquots and stored
in separate cryogenic vials for each assay to eliminate thawing and
refreezing for different assays.
Blood biochemistry.
Before analysis was done, the serially collected serum hormone samples
were pooled by placing an equal aliquot from each of the eight time
points into a vial. The pooled sample was then gently mixed and
analyzed by immunoassay. GH, cortisol, PRL, and IGF-I (acid-ethanol
extracted) were measured by using kits from INCSTAR (Stillwater, MN),
while T, Free-T, LH, estradiol, and DHEA-S were analyzed by using kits
from Diagnostic Products (Los Angeles, CA). SHBG was measured by using
kits from Wein Laboratories (Succasunna, NJ). Insulin,
T3, and
T4 were measured outside our laboratory (by Dr. Anthony Hackney, University of North Carolina, Chapel Hill, NC) as were growth homone binding protein (GHBP) and
IGFBP3 (by Genentech, South San Francisco, CA). Assay reference standards for insulin, LH and PRL were World Health Organization 1st
International Reference Preparation (IRP) 66/304, 2nd IRP-human menopausal gonadotropin, and 1st IRP 75/504, respectively. All samples
from a given subject for a specific hormone were tested within the same
assay. Samples were tested in triplicate, except that those measured
outside our laboratory were tested in duplicate. For those hormone
analyses completed in our laboratory, a control serum (CON6;
Diagnostics Products, Los Angeles, CA) was tested a minimum of five
times to determine an intra-assay and interassay (when applicable)
coefficient of variation. The intra-assay coefficient of variation
ranged from 2.0 to 9.6%, whereas the interassay variation ranged from
7.7 to 12.0%.
Hemoglobin concentrations (Radiometer A/S, Copenhagen, Denmark) and the
hematocrit were measured a minimum of three times for each sample.
Serum osmolality was determined by freezing point depression (Osmette A
automatic osmometer; Precision Systems, Natick MA).
Statistical analysis.
Data were analyzed for the main effects of group and time and for the
interaction of group by time with a 2 (group) × 3 (test period)
repeated-measures analysis of variance (ANOVA). A Newman-Keuls post hoc
analysis was used to locate statistical significance when an ANOVA was
significant. A simple effects post hoc analysis was performed on
significant interactions. The effects of dietary restriction and
wrestling training were shown through significant interaction effects,
which is the focus of the analysis. For all statistical comparisons, a
significance level of P 
0.05 was chosen.
RESULTS
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, Wrestlers, n = 9; 
, controls,
n = 7; GHBP, growth hormone-binding
protein; IGFBP-3, insulin-like growth factor I-binding protein 3. Like letters indicate P 0.05.
The wrestlers' T and Free-T concentrations (Fig. 2) decreased from preseason to late season and then increased from late season to postseason. However, the wrestlers' LH concentrations were unchanged and remained in the normal physiological range (Table 1). Serum concentrations of SHBG (Fig. 2) were elevated from preseason to late season but returned to baseline concentrations during the postseason. The wrestlers also had reduced serum concentrations of DHEA-S in the late season, although the wrestlers' concentrations were never below those of the controls (Fig. 2). The wrestlers' mean serum concentrations of other hormones that can modulate hypothalamic-pituitary-testicular activity, including estradiol, prolactin, and cortisol, were not significant for the interaction and remained in normal physiological ranges (Table 1). Serum concentrations of insulin, T4, and T3 did not differ between groups or over time (Table 1).
, Wrestlers,
n = 9; , controls,
n = 7. Like letters indicate
P 0.05.
DISCUSSION
The present study is unique as the first to investigate changes in the GH-IGF-I and pituitary-testicular axes (including binding proteins) of adolescent wrestlers over a sport season. The results indicate that dietary restriction while training for wrestling produces a partial GH resistance and a disruption of the pituitary-testicular axis. However, except for Free-T, all of the hormone concentrations remained in the normal physiological range, and we have shown that there is little effect on linear bone growth or pubertal maturation (23, 24).
Wrestlers lose weight through a combination of dietary restriction and dehydration that has the potential to hemoconcentrate the hormones. However, the hematocrit and serum osmolality were not significantly changed, and rather than the increase expected with dehydration, the wrestlers' hemoglobin concentration decreased slightly.
Although the wrestlers' GH concentrations increased and GHBP and IGF-I concentrations decreased in the late season (Fig. 1), the concentrations remained within the normal range (14-16). Previously, McMurray et al. (18) reported a significant increase in GH and reduction in IGF-I concentrations of collegiate wrestlers. The increased GH concentrations (partial GH resistance) in the present study may have been caused by a reduced negative hypothalamic feedback by IGF-I or a decrease in GHBP concentration. The GHBP concentration, which signifies GH-receptor number (13), is reduced with undernutrition lasting as little as 5 days or as long as an exacerbation of anorexia nervosa (2, 4, 8). The growth effects of GH are enhanced by GHBP and GH secretion would need to increase to account for the reduced GHBP concentration to ensure continuation of normal growth (15).
Most circulating IGF-I is bound to IGFBP3 (25), which inhibits IGF-I action, because IGF/IGFBP3 complexes do not bind to IGF-I receptors (17). Furthermore, IGFBP3 inhibits IGF-I action when present in an excess molar ratio (5). In the present study, IGFBP3 concentrations were not significantly changed (Fig. 1) and remained in the normal range (3). However, as in the present study, others have shown that short- (21) or long-term (4) undernutrition produces a greater percent reduction in IGF-I than in IGFBP3.
The pituitary-gonadal axis was also affected by the dietary restriction (Fig. 2). In the late season, the wrestlers had low-normal T (12) and low Free-T concentrations (6). In previous investigations that utilized single blood samples from collegiate wrestlers (7, 28), reductions in T were also found. Free-T concentrations have not been previously reported in wrestlers.
Albumin and SHBG are plasma proteins that limit the amount of biologically active Free-T (26). Serum albumin concentrations of adolescent wrestlers do not change over a sport season (10). Although the wrestlers' SHBG concentrations increased (Fig. 2), they remained in the normal range (9), and their Free-T/total T ratio was not changed. Reductions in T and Free-T without a change in serum binding indicate an increased clearance or decreased production of T. There is no evidence of chronic changes in the clearance of T in athletes, and the metabolic clearance of T is directly related to Free-T concentrations (29). Thus we conclude that the wrestlers' low T concentrations were caused by a reduction in T production during the season.
As found in previous investigations (7, 28), the wrestlers' LH concentration (Table 1) remained unchanged and in the normal range (12). However, alterations in the pulsatility of LH during sleep, rather than changes in tonic morning LH concentrations, are more likely to affect the stimulation and release of T (30). We did not measure serial nocturnal LH concentrations, but the reduction in morning T concentrations suggests altered LH pulsatility.
Serum PRL, estradiol, and cortisol concentrations (Table 1) were not changed in a manner that would suggest a differential effect of weight loss and wrestling training, and all values remained in the physiological range (12). Using single blood samples, Strauss et al. (28) and Hackney and Sinning (7) found that the in-season cortisol concentrations of collegiate wrestlers were not significantly elevated compared with postseason concentrations but that in-season PRL concentrations were indeed reduced.
DHEA-S stimulates skeletal and pubertal maturation (20). Although the wrestlers' DHEA-S concentrations were significantly reduced in the late season (Fig. 2), they were not less than those of the controls and remained in the normal range (22). Neither skeletal nor pubertal maturation was affected in the wrestlers.
In conclusion, there were alterations in the wrestlers' GH-IGF-I and pituitary-testicular axes, but only the Free-T concentrations were outside of the normal range. The in-season elevations in GH, with concomitant reductions in GHBP and IGF-I, that were reversed during the postseason suggest a reduction in GH-receptor number and a partial GH resistance during the season. Thus the GH-IGF-I axis is regulated by energy balance through the GH receptor, and the effects are reversible on reduction of the training load (energy expenditure) and increase in energy intake. Nonelevated LH with reduced T levels in the wrestlers suggests a central hypothalamic-pituitary-gonadal axis impairment.
ACKNOWLEDGEMENTS
We are indebted to Dr. Jim Blank, Kent State University, for use of the laboratory facilities required to complete the radioimmunoassay analyses. We thank Genentech, Inc., for completing the GHBP and IGFBP3 assays. We are especially indebted to Dr. Anthony Hackney of the University of North Carolina for completing the insulin, T3, and T4 assays. We thank Dr. Alan D. Rogol for suggestions during the preparation of the manuscript, and we thank the subjects, parents, and coaches for their enthusiastic support and cooperation.
FOOTNOTES
Address for reprint requests: J. N. Roemmich, Univ. of Virginia Health Sciences Center, Dept. of Pediatrics, Division of Endocrinology, Box 386, Charlottesville, VA 22908 (E-mail: jr5n{at}virginia.edu).
Received 26 July 1996; accepted in final form 6 February 1997.
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Weight loss and wrestling training: effects on nutrition, growth, maturation, body composition, and strength.
J. Appl. Physiol.
82:
1751-1759,
1997
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