Features of the development of somatotropic function of the pituitary gland and the adrenal cortex (cortisol) in boys aged 8-17 years
In order to find the functional reserve of pituitary gland and, to a certain degree, growth capabilities of the body, we made a comparative assessment of somatotropin dynamics in blood both in the state of relative rest and under various testing loads. For deepening the developed ideas of hormonal regulation of growth in the course of puberty, the simultaneous examination was conducted to study the response of pituitary gland (with respect to somatotropin) and adrenal cortex (with respect to cortisol) under physical load with PWC <sub> 170 </sub> power and under the maximum load with the capacity increasing on a step by step basis (load was applied down to the limit by means of bicycle ergometer). Quantitative definition of somatotropin (STG) and cortisol in plasma of blood was carried out by a radioimmunoassay technique with use of standard sets of CEA-IRE-SORIN (France). Results of research show that the activity of somatotropic function of the pituitary gland increases under the physical load with PWC <sub> 170 </sub> power. Pituitary gland response (with respect to somatotropin) in the 45th minute is more significant than response in the 15th minute after the load. Under the same load conditions, concentration of cortisol in the 15th minute decreases on average by 1,4 times (in comparison with initial level), and in 45 minutes comes back to initial level. In each specific case, the trend of response (increase or decrease), incremental value of somatotropin and cortisol, as well as the rate of response were subject to the value of the initial level of pituitary gland and adrenal cortex activity. Two physiologically equivalent types of response of pituitary gland (with respect to somatotropin) and adrenal cortex (with respect to cortisol) were observed - increase (with relatively low initial level) and decrease (with relatively high initial level) of the concentration of hormone in blood. In comparison with the adrenal cortex (with respect to cortisol) the response of pituitary gland (with respect to somatotropin) is more long-term and stable, however the adrenal cortex responses quicker to the load. This shows a cortisol role in fast mobilization of adaptive opportunities of a body under the impact of physical activities. Under the influence of physical load of higher power during the work on the bicycle ergometer somatotropin concentration reaches its maximum value immediately after the load and remains at such level until the 45th minute. Cortisol concentration decreases immediately after the load and in 15 minutes significantly increases and remains at stable level until the 45th minute.