The pineal gland in relation to growth and development in children.

The biorhythm of melatonin in human newborns is established later than that of either serotonin or N-acetylserotonin. Towards the end of the first year of life, the melatonin rhythm is a well established phenomenon and its nocturnal increment is equal to that seen in the pre-school children. Following this period the magnitude of nighttime melatonin increment starts declining and is closely associated with advancing skeletal age. This association between the magnitude of nocturnal increment and skeletal age is also noted in pathological subjects, lower skeletal age with greater magnitude of increment or advanced skeletal age with less increment. Although no inverse relationship between plasma melatonin and gonadotropins could be detected in children, there emerged a marked negative association between melatonin and growth hormone. GRF-induced GH stimulation suppressed melatonin in children as well as in adults. Melatonin pretreatment blocked GRF-induced increment of GH in rats. When animals were given either melatonin or growth hormone, one suppressed the other. It is possible that melatonin-induced growth hormone suppression is somatostatin mediated.