Melanotropic hormone (melanotropin, MSH) is a hormone that determines the color of the skin. It is mainly produced in response to solar radiation and causes the skin to darken, i.e. sunbathing. It is worth finding out how it is produced, what is its importance and what other activities melanotropin has.
Melanotropic hormone( melanotropin ,MSH ) is produced and secreted into the blood by the pituitary gland the brain, or rather its intermediate part.
Melanotropin is a polypeptide hormone, it is made of a substance called proopiomelanocortin, from which successive fragments of oligopeptides are detached.
The tan process is called post-translational proteolysis, and its products, apart from melanotropin, are also e.g. adrenocorticotropic hormone regulating the function of the adrenal glands.
From a biochemical point of view, there are three melanotropic hormones: α-MSH, β-MSH and γ-MSH, their action is identical, they differ only slightly in the strength of the impact.
Melanotropin: MSH action
Melanotropin primarily affects melanocytes. These are cells that produce and store the pigment - melanin, are found in the basal layer of the epidermis, and in a small amount also in the eye and inner ear, regulating the color of the structures in which they are located, especially skin and hair.
The effect of melanotropin is mainly to stimulate melanogenesis, i.e. the process of melanin synthesis in melanocytes, which results in a darker color of the skin or hair.
In addition, due to its origin and the way it is produced, the melanotropic hormone is structurally similar to the adrenocorticotropic hormone, therefore it has a slight similar effect to it.
It involves stimulating the secretion of cortisol and some androgens, hormones responsible for the stress response and male appearance, respectively.
It has also been noticed that melanotropin weakly suppresses appetite and affects sexual arousal.
The much less important role of MSH is the regulation of rhodopsin resynthesis (a pigment present in the retina) and the adaptation of eyesight to darkness, the importance of melanotropin in this process is minimal, as this regulation occurs through changes in pupil size.
Melanotropic hormone: secretion regulation
Melanotropin isreleased mainly in response to UV radiation to produce more of the pigment - melanin. By increasing the amount of pigment, the deeper, more sensitive layers of the skin are protected against radiation.
For unknown reasons, the concentration of melanotropin increases during pregnancy, which translates into a slightly darker skin color in pregnant women.
Inhibition of melanotropin secretion occurs in response to cortisol, adrenaline and noradrenaline - hormones produced by the adrenal glands, this is the so-called feedback.
This regulation is based on MSH stimulating the production of these hormones, and their growth is inhibited by MSH, thanks to which the concentration of these substances is relatively constant.
It is a common precursor and the similarity of the structure of melanotropin from adrenal hormones causes that in hypothyroidism of this organ, we can observe a dark color of the skin, i.e. cisia.
This is because a deficiency of adrenal hormones stimulates the pituitary gland to secrete ACTH, which, due to its similarity to MSH, stimulates melanin synthesis in the skin.
A relationship between the concentration of MSH and leptin has also been noticed, it increases the production of the melanotropic hormone, its main action is to regulate food intake and energy management. Leptin is produced by adipocytes, i.e. cells of adipose tissue.
Synthetic Melanotropin
Advanced laboratory methods have made it possible to synthesize MSH analogues - hormones with a different structure but similar effect. Their use in medicine is very limited and they are not approved for sale in all countries.
The first studies report the possibility of treating them with: porphyria, some skin cancers, and libido disorders.
Melanotropic hormone is produced by the pituitary gland, and its effectors are melanocytes, the stimulation of which increases the amount of pigment in the skin and makes it darker.
Increased production of MSH occurs primarily in response to UV radiation, i.e. solar radiation.