Also called insulin-like growth factor (IGF-1), somatomedin C is considered a more accurate reflection of the blood concentration of hGH because such variables as time of day, activity levels, or diet do not influence test results.
Nonpituitary causes of reduced somatomedin C include malnutrition, severe chronic illness, severe liver disease, hypothyroidism, and Laron's dwarfism.
Somatomedin C is part of a group of peptides, called somatomedins, through which hGH exerts its effects.
The somatomedin C test also requires a fasting blood sample.
Abnormally low levels of somatomedin C will require further investigation, so doctors may perform the hGH stimulation test to diagnose hGH deficiency.
The somatomedin C test is usually ordered to help detect pituitary abnormalities, hGH deficiency, and acromegaly.
Levels of somatomedin C do depend on hGH levels, however, and typically somatomedin C levels will be low when hGH levels are deficient.