HORMONAL RESPONSES TO EXERCISE IN BOYS IN THE COURSE OF SEXUAL MATURATION

HORMONAL RESPONSES TO EXERCISE IN BOYS IN THE COURSE OF SEXUAL MATURATION

T.Smirnova, K. Karelson, M. Viru, M. Muur, A. Viru

Institute of Exercise Biology, University of Tartu,
Estonia

In the course of sexual maturation, alterations in the hormone control of metabolism both at the level of regulation of endocrine function and at level of hormone reception. Accordingly, hormone responses to various actions have to be adjusted to a new situation. Several studies point on the possibility of alterations in exercise-induced hormonal responses during puberty [1-5]. However, the maturation-related pecularities of hormone responses during acute exercise have been established by cross-sectional studies and verified only in one longitudinal study on girls [6].

The present study has been aimed to test the alterations in exercise-induced hormonal responses in boys with transition from one sexual maturation stage into the next stage.

MATERIALS AND METHODS. Study persons were 15 boys. 5 of them were studied during three and 10 boys during two years. At the beginning of study 11 boys were in age range 10 to 12 years, others in age 13 to 14 years. The sexual maturation stage was determined according to the basal level of testosterone in blood and by the Tanner`s five-stage scale [7]. An informed consent was obtained from all the children, their parents and the principal of school. The design of research was approved by the Ethics Commission of the Medical Faculty of the University of Tartu.

Exercise test (an incremental ergocycling exercise for determination of VO2max and 20-min exercise at 60% of VO2max) were performed in separate days. The children were asked not to performed any exercises before the testing as well as during the preceding day. The nutritional regime was controlled. Blood samples were withdrawn from antecubiual vein before 20-min exercise and within 5 min after the end of exercise. Blood samples were immediately centrifuged. Samples of serum were immediately cooled with the aid of ligued nitrogen and stored at -200C. Cortisol, growth hormone and testosterone concentration were determined by radioimmunological method.

RESULTS. In boys of sexual maturation stages I (basal testosterone level in blood <0,5 nmol * l-1) the 20-min exercise did not increase the blood cortisol level (Table 1). Increase was found neither in blood testosterone concentration. After transition to the sexual maturation stage III (basal testosterone level 3,1-12,0 nmol * l-1) a pronounced increase appeared in cortisol concentration and in majority cases in testosterone concentration. A trend to increase was found in basal level of growth hormone with reaching stage II. In all boys exercise induced an increase of growth hormone concentration.

DISCUSSION. The obtained results indicated that in exercise increase of blood cortisol levels is not common in prepubertal boys (sexual maturation stage I) and at the beginning of sexual maturation (stage II). The significant response appears in stage III (an intersification of sexual maturation). In accordance with those results Scwenk and Wennenman [8] observed in physically advanced 12-13 year old boys an increase of corticosteroid excretion during cycling 24 km while in boys with retarded physical development corticosteroid excretion decreased as it was found also in all 11-year old boys. Differently from the present results obtained in boys, in girl a significant cortisol response was found in sexual maturation stage II [6].

It has been reported that growth hormone response is lower in prepubertal than in pubertal and postpubertal boys [1,4,5]. Our results failed to confirm this trend.

In prepubertal boys as well as beginning of puberty low possibilities for testosterone production associated with the lack of testosterone response during exercise.

Table 1

HORMONE LEVELS BEFORE AND AFTER 20 MIN EXERCISE IN CIRCUMPUBERTAL BOYS (MEAN ± SD)

  Cortisol nmol* l-1 Growth hormone g*ml-1 Testosterone nmol* L-1
Before After Before After Before After
Stage I in the 1st year

Stage II in the2nd year

312 ± 116

262 ± 233

311 ± 150

267± 274

2,8 ± 3,0

2,9 ± 3,4

47,5 ± 41,1*

35,7± 35,5*

0,4 ± 0,4

0,6 ± 0,6

0,4± 0,4

0,7 ± 0,7

Stage I in the 1st year

Stage II in the 2nd year

268 ± 99

368 ± 146

273 ± 57

364 ± 113

4,9± 4,5

6,1 ± 10,0

41,3 ± 20,4*

32,6 ± 19,7*

0,8± 0,4

3,1 ± 2,5

0,8 ± 0,3

2,7 ± 0,6

Stage I in the 1st year

Stage II in the 2nd year

258± 89

214 ± 99

358 ± 154

347± 65*

2,3 ± 1,7

3,8 ± 3,9

47,2 ± 10.0*

34.8 ± 17,6*

1,9 ± 1,2

2,9 ± 2,1

9,1± 3,0

11,7 ± 4,2*

* - Significant change according to paired t-test

REFERENCES

1. Bouix O, Brun JE, Fedou C, Ravnaud E, Kerdalhue B, Lenoir V, Orsetti A. Plasma beta-endorphine, corticotropine and growth-hormone responses to exercise in pubertal and postpubertal children. Horm. Metab. Res. 1994, 26 195-199.

2. Delmarche P, Gratas-Delmarche A, Monnier M, Mavet MH, Kouby HE, Favier R. Glucoregulation and hormonal changes during prolonged exercise in boys and girls. Eur. J Appl. Physiol. 1994, 69, 6-8.

3. Fahey DT, Valle-Zuris AD, Oehlsen G, Trieb M, Seymour J. Pubertal stage differences in hormonal and hematological responses to maximal exercise in males. J Appl. Physiol. 1979, 46, 823-827.

4. Marin G, Domene HM, Barnes KM, Blackwell BJ, Cassorla FG, Cutler GB. The effects of estrogen priming and puberty on the growth-hormone response to standardized treadmill exercise and arginine-insuline in normal girls and boys. J Clin. Endocrin. Metab. 1994, 79, 537-541.

5. Wirth A, Trager E, Scheele k, Maver D, Diehm K, Reischle K, Weicker H. Cardiopulmonary adjustment and metabolic responses to maximal and submaximal physical exercise of boys and girls at different stage of maturation. Eur. J Appl. Physiol. 1978, 39, 229-240.

6. Viru A, Laaneots L, Karelson K, Smirnova T, Viru M. Exercise-induced hormone responses in girls at different stages of sexual maturation. Eur. J Appl. Physiol. 1998 (in press)

7. Tanner JM. Growth at adolescence. 2nd edit., Oxford, Blackwell, 1962.

8. Schwenk A, Wennenmann J. Die Harnsteroidauscheidung bei Frun und Spatereifenden Jungen im Pubertatsalter unter korperlicher Belastung. Z Kinderheilk 1953, 73, 407-420.


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Hormonal responses to exercise in boys in the course of sexual maturation / Smirnova T. [и др.] // Человек в мире спорта: Новые идеи, технологии, перспективы : Тез. докл. Междунар. конгр. - М., 1998. - Т. 1. - С. 115-117.