Melanocyte-stimulating Hormone (MSH)

Hormones are known to be released in trace amounts to act on their selected target sites by communicating with the cells and they do not contain many nutrients. The melanocyte-stimulating hormones (MSH), also known as melanotropins (tropins are known to be activating hormones) or intermedins (as it is secreted from pars intermedia of adenohypophysis), belong to a diverse group of peptide hormones and neuropeptides produced by cells in the pars intermedia of the pituitary gland, which is attached to the Hypothalamus part of our brain by the attached stalk called Infundibulum. 

Source of Melanocyte-stimulating hormone:

Pituitary hormones, though control the release of hormones, are also regulated by the hypothalamus. The pituitary has two main regions divided on the basis of direct and indirect control by the hypothalamus namely, adenohypophysis and neurohypophysis, respectively. There are three subdivided regions divided on the basis of secretions, inside the pituitary gland (Pars distalis and Pars intermedia belong to the adenohypophysis region). Amongst Pars nervosa, Pars intermedia, and Pars distalis, only Pars intermedia is known to secrete MSH. It assists in the protection and maintenance of the skin from UV rays, the development of pigmentation, and even appetite control. The MSH after being released from the pituitary gland located inside the brain acts on our skin cells.

Role of MSH in our body:

MSH, as stated above, has a major role to play in human skin pigmentation or colour. It aids in the protection of the skin from UV rays (upon indefinite exposure to UV rays, mutations in the human body can cause skin cancer). During the trimesters of pregnancy, MSH levels elevate in humans. Increased pigmentation in pregnant women is caused by this, as well as increased estrogens. 

Different amounts of MSH have a limited role to play in skin colour variation. Since MSH directly affects skin pigmentation, MSH only stimulates it. Suppose, a human is exposed to sunlight for a longer duration of time and as a result, we will observe a darkening of the skin in the exposed area and this is due to the deposition of melanin in that particular region of skin. A person with more melanin under their skin surface would have darker skin, in comparison to those who don’t. People living in regions with greater exposure to sunlight have been found to be having more MSH and hence, melanin in their bodies.

However, there are abnormalities in hormone receptors in many people who don’t tan well, causing them to not respond to MSH in the blood. Melanin is a pigment that gives humans and animals their skin, eye, and even hair colour. Melanin provides colour and pigmentation for the skin cells but it also repels damaging and harmful UV rays and protects them from cellular damage. 

Diseases caused due to deficiency of MSH:

Prolonged deficiency of melanin of skin can be caused due to less secretion of MSH in human blood and as a result, the skin would become more prone to UV radiation. These radiations are the reason why certain mutations occur in our genes and as an impact of that, oncogenes get activated. In humans, an increase in MSH amount in blood circulations results in abnormally darker skin. Increased inflammation in body parts, pain in body parts, and sleeping issues can result from a lack of the melanocyte-stimulating hormone, as well as a drop in antidiuretic hormone levels, which promotes thirst and frequent urination. Increased intake than a normal diet and even obesity can also be observed by a lack of melanocyte-stimulating hormone.

Excess adrenocorticotropic hormone (ACTH) in Cushing’s illness can cause hyperpigmentation (skin abnormality). Skin darkening (hyperpigmentation) is common in people with primary Addison’s disease, even in areas that aren’t exposed to the sun; common sites include skin creases ( on the back or inside of hands), the skin found on the inside of the cheek (buccal mucosa), and the nipple; new scars become hyperpigmented, but older scars don’t. This usually happens because MSH and ACTH have the same precursor molecule.

Conclusion:

The hormone, MSH which is released from the pituitary gland, regulates human skin pigmentations, primarily. These hormones are released in trace amounts but they act on their target sites by protecting the skin from harmful UV radiations. Melanocyte stimulating hormone belongs to the group of peptide hormones that also act as neuropeptides. It is also controlled by the hypothalamus which regulates pituitary hormones and MSH has a role to play even in human pregnancy. Different amounts of melanin are secreted due to MSH is the reason why there are different skin pigmentation in different humans along with the skin, melanin also is responsible for giving the pigment to the eyes and the hair.