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Gábor A. Tóth1, Botond L. Buda2
1Berzsenyi Dániel College, Research Center for Anthropology, Szombathely, Hungary
2Privte Practice for Neurologic Consultations, Szombathely, Hungary
Growth is the product of the interaction of genetic codes, growth factors, and many hormones. Some hormones have important effects on growth, maturation, and body composition. The horomones considered are estradiol, testosterone, thyroid hormone, adrenal hormone, growth hormone (GH), IGF-1, insulin and leptin. Growth hormone is essential for normal growth. Its effects are both direct and indirect.
Growth hormone is synthetized and secreted by specialized cells in the anterior pituitary gland. Another hypothalamic hormone, growth hormone releasing hormone, stimulates the synthesis of GH and along with other agents, causes the release of GH into the bloodstream. Growth hormone is secreted in pulses occurring approximately every 3 hours, depending on age, physical exercise and sleep pattern. The exact basis for the temporal association between slow wave sleep and GH secretion is not known but it probably involves neuroendocrine mechanisms, such as variations in central catecholaminergic and cholinergic activities leading to hyperactivation of GHRH-secreting neurons and concomitant reduction of somatostatin activity.
The pulsatile release of GH from the anterior pituitary occurs throughout the day, but the largest bursts usually occur at night with the onset of sleep. They occur in the early part of deep sleep, and children have a greater percentage of deep sleep than adults. Thus, the continous monitoring of circulating growth hormone is essential. Although the largest pulses of growth hormone ordinarily occur during sleep, other factors can influence growth-hormone levels, including physical activity, nutritional status, and psycholoigical and social stress.