The second type of stimulus that provokes GH release is nonspecific and noxious such as cold exposure, fright or severe muscular exercise. Growth hormone therefore has powerful effects on growth and metabolism. Lack of adequate production leads to dwarfism whereas excessive secretion leads to giantism or acromegaly. The administration of GH in a normal individual produces complex metabolic effects. Long term release may lead to growth but growth is complex and involves cell multiplication and net protein synthesis.
Malnutrition can have an effect at any time of development but is most profound early in life.
The final height of an individual cannot be increased beyond a genetically determined maximum by overfeeding. During development in humans there are 2 stages of rapid growth, the first within 2 years of life and the second during puberty. The growth in height is not necessarily correlated with the rates of growth of specific organs. There are also the obvious sex differences in growth rates. Growth is obviously complex and the most important hormones that influence growth include, growth hormone, thyroid hormones, insulin, testosterone and oestrogen.