Abstract
Objectives
Overtraining syndrome (OTS) leads to worsened sports performance and fatigue. The
pathophysiology of OTS has not been entirely elucidated, and there is a lack of accurate
markers for its diagnosis. Changes in hormonal responses implicated in OTS were stimulated
by exercise, which has limited their interpretation. Hence, we aimed to evaluate growth
hormone (GH) and prolactin responses to a gold-standard and exercise-independent stimulation
test, the insulin tolerance test (ITT).
Design
Volunteers were recruited and divided into OTS-affected athletes (OTS), healthy athletes
(ATL), and healthy non-active subjects (NCS) groups, after general and specific inclusion
and exclusion criteria.
Methods
We evaluated the responses of growth hormone (GH) and prolactin to the ITT, and compared
between groups.
Results
A total of 51 subjects were included (OTS, n = 14, ATL, n = 25, and NCS, n = 12). OTS disclosed significantly lower basal levels of GH (p = 0.003) and prolactin (p = 0.048), and GH (p = 0.001) and prolactin (p < 0.001) responses to ITT (p = 0.001), compared to ATL, but similar to NCS. OTS showed a later rise in GH levels
in response to hypoglycemia, compared to ATL, but not to NCS. We suggest cutoffs for
GH and prolactin levels to aid in the diagnosis of OTS.
Conclusions
OTS-affected athletes show reduced GH and prolactin basal levels and responses to
a non-exercise stress test compared to healthy athletes, but not to sedentary subjects.
Keywords
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Article info
Publication history
Published online: November 15, 2017
Accepted:
October 31,
2017
Received in revised form:
September 2,
2017
Received:
June 29,
2017
Identification
Copyright
© 2017 Published by Elsevier Ltd on behalf of Sports Medicine Australia.
