squeegee
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http://www.hormones.gr/49/article/article.html
Abstract
Hormones influence the development and function of human skin which also produces and releases hormones. Recently attention has been focused on identifying and understanding the complex endocrine properties of human skin, such as expression and function of specific hormone receptors, synthesis of hormones from major classes of compounds used by the body for general purposes, organized metabolism, activation, inactivation and elimination of the hormones in specialized cells of the tissue, exertion of biological activity and release of tissue hormones in the circulation. Specifically, hormones exert their biological effects on the skin through interaction with high-affinity receptors, such as several receptors for peptide hormones and neurotransmitters, steroid and thyroid hormones. Hormones exhibit a wide range of biological activities on the skin with distinct effects caused by growth hormone/insulin-like growth factor-I, neuropeptides, sex steroids, glucocorticoids, retinoids, vitamin D, peroxisome proliferator-activated receptor ligands, eicosanoids, melatonin and serotonin. Human skin produces, activates or inactivates metabolically numerous hormones which are probably important for skin functions but also for functions of the entire human organism, such as sex hormones, especially in aged individuals, insulin-like growth factor and -binding proteins, neuropeptides, prolactin, catecholamines, retinoids, steroids, vitamin D and eicosanoids. These functions are undertaken in most cases by different skin cell populations in a coordinated way, indicating the endocrine autonomy of the skin. Characteristic examples are the metabolic pathways of the corticotropin-releasing hormone/propiomelanocortin axis, steroidogenesis, vitamin D and retinoids. The human skin is, thus, the largest, peripheral endocrine organ.
Androgens:The biological activity of testosterone on the skin is induced in large part by its conversion to 5α-DHT by 5α-reductase[SUP]81,82[/SUP]. Testosterone and 5α-DHT, being the tissue active androgens, stimulate 5α-reductase mRNA and 5α-reductase activity and their effects are mediated through their binding to the AR. They stimulate proliferation of target cells, such as sebocytes and dermal papilla cells[SUP]83-86[/SUP]. In addition, there is evidence that the effect of androgens on human sebocyte proliferation depends on the area of skin from which the sebaceous glands are obtained; facial sebocytes are mostly affected[SUP]83,87[/SUP]. Androgens as single compounds seem to be unable to modify sebocyte differentiation[SUP]56[/SUP], which is stimulated by co-incubation with PPARγ ligands[SUP]88[/SUP]. Dermal papilla cells mediate the growth-stimulating signals of androgens by releasing growth factors that act in a paracrine fashion on the other cells of the follicle[SUP]5,86[/SUP]. Excessive amounts of tissue active androgens were shown to induce apoptosis of dermal papilla cells through the bcl-2 pathway[SUP]89[/SUP]. In aged skin, lower serum levels of testosterone and gradual decline in DHEA and DHEA sulfate are detected, at least in males[SUP]78[/SUP]. Unexpectedly, testosterone has been reported to perturb epidermal permeability barrier homeostasis.[SUP]90[/SUP]
Abstract
Hormones influence the development and function of human skin which also produces and releases hormones. Recently attention has been focused on identifying and understanding the complex endocrine properties of human skin, such as expression and function of specific hormone receptors, synthesis of hormones from major classes of compounds used by the body for general purposes, organized metabolism, activation, inactivation and elimination of the hormones in specialized cells of the tissue, exertion of biological activity and release of tissue hormones in the circulation. Specifically, hormones exert their biological effects on the skin through interaction with high-affinity receptors, such as several receptors for peptide hormones and neurotransmitters, steroid and thyroid hormones. Hormones exhibit a wide range of biological activities on the skin with distinct effects caused by growth hormone/insulin-like growth factor-I, neuropeptides, sex steroids, glucocorticoids, retinoids, vitamin D, peroxisome proliferator-activated receptor ligands, eicosanoids, melatonin and serotonin. Human skin produces, activates or inactivates metabolically numerous hormones which are probably important for skin functions but also for functions of the entire human organism, such as sex hormones, especially in aged individuals, insulin-like growth factor and -binding proteins, neuropeptides, prolactin, catecholamines, retinoids, steroids, vitamin D and eicosanoids. These functions are undertaken in most cases by different skin cell populations in a coordinated way, indicating the endocrine autonomy of the skin. Characteristic examples are the metabolic pathways of the corticotropin-releasing hormone/propiomelanocortin axis, steroidogenesis, vitamin D and retinoids. The human skin is, thus, the largest, peripheral endocrine organ.
Androgens:The biological activity of testosterone on the skin is induced in large part by its conversion to 5α-DHT by 5α-reductase[SUP]81,82[/SUP]. Testosterone and 5α-DHT, being the tissue active androgens, stimulate 5α-reductase mRNA and 5α-reductase activity and their effects are mediated through their binding to the AR. They stimulate proliferation of target cells, such as sebocytes and dermal papilla cells[SUP]83-86[/SUP]. In addition, there is evidence that the effect of androgens on human sebocyte proliferation depends on the area of skin from which the sebaceous glands are obtained; facial sebocytes are mostly affected[SUP]83,87[/SUP]. Androgens as single compounds seem to be unable to modify sebocyte differentiation[SUP]56[/SUP], which is stimulated by co-incubation with PPARγ ligands[SUP]88[/SUP]. Dermal papilla cells mediate the growth-stimulating signals of androgens by releasing growth factors that act in a paracrine fashion on the other cells of the follicle[SUP]5,86[/SUP]. Excessive amounts of tissue active androgens were shown to induce apoptosis of dermal papilla cells through the bcl-2 pathway[SUP]89[/SUP]. In aged skin, lower serum levels of testosterone and gradual decline in DHEA and DHEA sulfate are detected, at least in males[SUP]78[/SUP]. Unexpectedly, testosterone has been reported to perturb epidermal permeability barrier homeostasis.[SUP]90[/SUP]
