Neurohumoral mediation of exercise-induced growth. In the course of a life, control of growth undergoes remarkable changes. Over a life, the scope of growth changes from the primary guidance of body growth to a more restricted role in the maintenance, repair, and hypertrophy of musculoskeletal tissues.
Incremental growth is vulnerable to energy deficits.
Rate of growth is dependent upon nutrient availability. In young organisms forced to exercise and denied abundance of food at this nutritionally-dependent stage of growth, nutrient energy is diverted from growth and the final body stature is stunted, the more so the more rapid the rate of growth. It stimulates the release of HGH, thyroid hormones, and sex steroid hormones in a fashion that favors their anabolic actions by channelling of the nutrient energy toward the biosynthetic processes of growth. In the fourth and final stage of neurohumoral control of growth, from puberty through late adulthood, the brain has assumed an inhibitory control over growth so that little if any incremental growth occurs and anabolic hormonal actions are limited to maintenance and repair of lean body tissues. Nutrient intake per unit weight declines since energy no longer is needed for incremental growth.