Assay of Growth Hormone-like Activity in Blood Plasma A Comparison of two Methods

Growth hormone has been shown to increase the uptake of sulfur-35 into tibial epiphyseal cartilage as well as to increase the width of the cartilage plate in linear fashion with increasing dosage. That growth hormone is not alone responsible has been experimentally demonstrated by the increase in both responses effected by injections of human albumin and insulin, and the decrease produced by ACTH. Tests on human blood plasma indicated the following: (1) The blood specimens of patients with the same clinical syndrome do not always yield similar values when tested by these methods. (2) The blood of hypophysectomized patients can increase both the sulfur uptake and epiphyseal cartilage width. (3) Blood of patients with active acromegaly does not always stimulate the sulfur uptake or increase the cartilage width. (4) In a number of cases in which the sulfur uptake was increased, the tibia test was negative. Conversely, the tibia test occasionally was positive when there was no increase in sulfur uptake. (5) In a few cases in which the tests were repeated on the same patient, the results were not in agreement. (6) In only 7 cases (of 40) was there good correlation between the two methods. Other growth factors in blood can interfere with the specificity of both methods for the measurement of growth hormone.