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Lack of sex differences in the IGF–IGFBP response to ultra endurance exercise
Author(s) -
Berg U.,
Enqvist J. K.,
Mattsson C. M.,
CarlssonSkwirut C.,
Sundberg C. J.,
Ekblom B.,
Bang P.
Publication year - 2008
Publication title -
scandinavian journal of medicine and science in sports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.575
H-Index - 115
eISSN - 1600-0838
pISSN - 0905-7188
DOI - 10.1111/j.1600-0838.2007.00758.x
Subject(s) - endurance training , medicine , exercise physiology , physical therapy , physical medicine and rehabilitation
The insulin‐like growth factor (IGF)–IGF binding proteins (BP) and the pituitary–gonadal axes were investigated during ultra endurance exercise in 16 endurance‐trained athletes (seven women). Median duration of the race was 6.3 days. Although food and drink were ad libitum , energy balance was negative. Blood samples were drawn before (PRE), at the end of (END) and 24 h after (POST24h) the race. Serum concentrations of total IGF‐I (t‐IGF‐I) and free IGF‐I (f‐IGF‐I) decreased by 33 (SD 38)% and 54 (19)%, respectively. The decrease in t‐IGF‐I appeared to be associated to the total energy deficit during the race. At END, the IGFBP‐3 fragmentation and IGFBP‐1 were increased but these changes did not predict changes in f‐IGF‐I. An increase in POST24h IGFBP‐2 levels in women was the only sex difference. Testosterone was decreased by 67 (12)% in the men and estradiol became undetectable in the women without any detectable increase in LH and/or FSH. In conclusion ultra endurance exercise results in similar IGF–IGFBP responses in men and women reflecting a catabolic state. IGFBP‐2 was the only exception, with increased levels in women after exercise. A concomitant decrease in gonadal hormones was not related to endocrine changes in the IGF–IGFBP axis but may be related to local changes in IGF‐I expression.