Abstract
Growth hormone (GH) promotes growth and development in children and is the meaningful co-regulator of the metabolism in adulthood. GH may act directly, through its receptor (GHR), as well as via mediators – insulin-like growth factors: IGF-1, i.e. somatomedin C and IGF-2. Moreover, GH and two growth factors are involved in the mechanisms of cell proliferation, differentiation and survival, hence their oncogenic potential is propounded. Indeed, GH, somatomedins and their receptors are found abundantly in normal and cancer cells in several tissues. It has been shown in animal and human trials that polymorphisms and mutations that increase signal transmission from the GH and IGF-1 receptor are associated with more frequent tumors development and reduce life expectancy. Numerous epidemiological studies have confirmed a clear relationship between GH/IGF-1 level in circulation and a cancer-dependent morbidity and mortality. It dictates caution in case of treatment with use of growth hormone. Such replacement therapy is recommended in cases of GH deficiency. In the common opinion of scientific societies such treatment is generally safe, although in some cases unambiguous opinion in this field cannot be determined yet. On the other hand, on the basis of available evidence, GH cannot be recommended for use by the healthy elderly (ani-aging medicine), bearing in mind that GH decline with age may represent a beneficial adaptation to ageing. Understanding the molecular mechanisms by which GH and GH-dependent growth factors affect cell metabolism and proliferation will allow to use them in oncology in the future.
Highlights
In the common opinion of scientific societies such treatment is generally safe, in some cases unambiguous opinion in this field cannot be determined yet
In target organs growth hormone stimulates synthesis of insulin-like growth factors, in particular somatomedin C, that is, insulin-like growth factor 1 (IGF-1), which is a mediator of several actions of Growth hormone (GH)
In the authors’ opinion the results show the need for caution during GH-treatment leading to an increase in IGF-1, in the elderly (43)
Summary
Growth hormone is produced in the pituitary gland. It is mainly release at night, under control of the hypothalamic factors: stimulating – growth hormone releasing hormone (GHRH). IGF-1 by the negative feedback loop inhibits the release of growth hormone from the somatotropic cells (1) Another somatomedin present in the circulation and some tissues, IGF-2 exhibits a much lower dependence on GH (2). Growth hormone secretion decreases with weight gain (higher BMI), increases after intensive physical activity and falls after a longer acting effort It is greater in women than in men and depends on age: since 35-40 year of age production of GH gradually decreases, so in the age of 70s it is reduced of 15-70% (3). These receptors, are called "blind", meaning that joining ligand do not pass the signal to the inside of the cell It seems, that their role is to block the action of growth factors by sequestration them from the receptors for IGF-1 and insulin (5, 6)
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