Insulin-like Growth factor 1
Insulin-like growth factor 1 is a protein that is encoded by IGF1 gene in humans. It is also known as somatomedin C. Some scientists call it a sulfation factor. The effects of this gene were called non-suppressible insulin-like activity in the 1970s. The molecular structure of Insulin-like growth factor 1 is similar to that of insulin.
This hormone plays a crucial role in the human body during childhood growth. In adults, the hormone has anabolic effects. A synthetic IGF-1 analog mecasermin helps in treating growth failure. Insulin-like growth factor 1 has 70 amino acids in one chain. It has three disulfide bridges. The molecular weight of Insulin-like growth factor 1 is 7,649 daltons.
Insulin-like growth factor 1 occurs naturally in blood and it regulates the effects that growth hormone has on human body. Among the normal functions of IGF-1 and growth hormones include bone and tissue growth. IGF I is usually formed in the tissues of the body, primarily as an endocrine hormone by the liver due to the presence of growth hormone in the body. Target tissues in autocrine/paracrine fashion also produce this hormone.
Factors that affect the synthesis of insulin-like growth factor 1 include the insensitivity of growth hormone, under-nutrition, lack of the receptors of growth hormone and failures of downstream signaling pathway. About 98 percent of Insulin-like growth factor 1 is bound to one out of 6 binding proteins.
In humans, IGF-1 is produced throughout the life of a person. Its production is at peak during puberty and at its lowest levels during old age and infancy. Levels of insulin-like growth factor 1 are increased by high protein intakes and they are independent of calorie consumption.
Among the factors that affect synthesis and circulation of IGF-1 include the genetic make-up of a person, age, exercise status, time, sex, nutritional level, estrogen status, xenobiotic intake, stress levels and body mass index among others.
Insulin-like growth factor 1 is among the potent activators of AKT signaling pathway. This is a stimulator of cell proliferation and growth. It also inhibits programmed cell death. IGF I binds the cell surface of at least two receptors. These are the insulin receptor and the IGF-1 receptor.
The inability of the body to respond to or to make IGF-1 causes growth failure. This can lead to a disorder called Laron dwarfism which does not respond to all treatments of growth hormone because the body lacks growth hormone receptors. People with this disorder have strikingly low diabetes and caner rates.
Levels of insulin-like growth factor 1 in the body can be measured in 10-1000ng/ml amounts. Since the levels of IGF1 do not fluctuate during the day, physicians use IGF-1 levels in testing excess and deficiency of growth hormone in gigantism and acromegaly.
The level of insulin-like growth factor 1 in the blood can be affected by liver disease, low levels of thyroid hormone, hypothyroidism and diabetes mellitus when uncontrolled.
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Sources
http://www.mayomedicallaboratories.com/interpretive-guide/?alpha=I&unit_code=35100
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1187088/
http://en.wikipedia.org/wiki/Insulin-like_growth_factor_1
http://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=167&ContentID=insulin_like_growth_factor