Bioassayable growth hormone activity in blood from healthy individuals and acromegalic patients

Biological growth activity (bioassayable GH) was determined in blood from healthy individuals and from patients with acromegaly using the rate of longitudinal bone growth in hypophysectomized rats with tetracycline as intravital marker. Also radioimmunoassayable GH and somatomedin A activity were determined. In pooled plasma or serum from normal subjects no bioassayable growth activity was demonstrated. In the clinically active acromegalic patients as a group as well as in one individual patient there was a significant (P less than 0.05) bioassayable growth activity in serum as compared to serum from normal subjects. The bioassay determination of GH in plasma/serum from normal subjects and acromegalic patients was hampered by the toxicity and the problems connected with the administration of large volumes.