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Insulin-like Growth Factor Type I, Somatomedin C


IGF 1, also called somatomedin C, is a protein produced by the liver, muscles and other tissues in response to growth hormone (GH) stimulation. IGF 1 promotes the growth of bone and muscle mass. Unlike GH, IGF 1 secretion is constant throughout the day. This means that blood levels of IGF 1 are an excellent reflection of GH secretion by the pituitary gland. Results are expressed in micrograms of IGF 1 per litre (µg/L), and the indicated reference values are based on the age and sex of the individual.

Normal levels of IGF 1 must be interpreted in context, as some individuals have normal levels of IGF 1 despite a GH deficiency. Low levels of IGF 1 usually indicate a GH deficiency or resistance to GH action. Low levels may also be caused by malnutrition (e.g., anorexia) or chronic kidney or liver disease.

High levels of IGF 1 generally indicate the presence of a pituitary tumour. IGF 1 levels are also high during growth and pregnancy. The presence of a GH-producing tumour may decrease the secretion of one or more other pituitary hormones (TSH, FSH, LH, prolactin, ACTH).

Term of the Week

Hot zone

A hot zone is a section of a facility (sometimes an entire facility or even a city district) where there is a high risk of contamination by patients with an infectious disease. All individuals entering a hot zone must respect appropriate protective measures. By analogy, “cold zone” and “warm zone” are used to refer to areas where there is no infected individual or only individuals suspected of having an infection.