A somatomedin assay using normal rabbit cartilage in clinical studies.

Somatomedin (SM) is a growth hormone (GH) dependent biological growth factor in serum. A SM assay, using mechanically sliced discs from young normal rabbit costal cartilage was developed and evaluated. This assay is as sensitive and precise, while much less laborious and costly, than the hypophysectomized rat cartilage SM assay. The elevated serum SM levels in patients with acromegaly returned to normal in two patients who were cured, and remained elevated in four incompletely treated patients. The low serum SM levels in five GH deficient patients were increased to normal after treatment with human GH. SM levels were normal in 10 patients with normal GH levels and short stature due to various causes. SM levels in serum were very low in patients with chronic renal insufficiency; the mean SM level increased significantly after renal transplantation, however, it increased only minimally after hemodialysis. SM levels were subnormal in 14 patients with sever chronic liver disease. One patient with severe acute liver disease had low serum SM levels which increased after clinical recovery. These results further suggest that the liver produces SM, while the relationship of the kidney and SM is not clear.