Discrepancies between bioassayable somatomedin activity and somatomedin C levels in acromegalic patients
Jasper, H.G.; Artese, R.; Molocznik, I.; Bruno, O.
Medicina 46(4): 440-444
1986
ISSN/ISBN: 0025-7680 PMID: 3574106 Document Number: 280550
Contrary to the high somatomedin biological activity levels previously reported we found normal serum somatomedin activity in every one of eleven acromegalic patients studied by means of a sulfation factor bioassay. Somatomedin C (Sm-C) serum levels were high in 7 out of 9 of these patients. On the whole, only 2 out of 12 patients studied had normal Sm-C levels, which is in accord with previous reports (normal controls 1.410 .+-. 0.269, acromegalics 6.030 .+-. 3.350, U/ml, .hivin.x .+-. SD, p < 0.001). Only one patient had been previously treated, so that therapy could not explain the normal somatomedin biological activity found in all the acromegalic patients. Moreover, normal GH levels could not explain the normal bioactivity, since eight out of eleven patients had high basal GH level. Serum inhibitory activity of the somatomedin biological activity was found in only one out of eight patients studied. A previous report using the same bioassay showed low somatomedin levels in patients with growth hormone deficit. Therefore, this particular sulfation factor bioassay seems geared to measure somatomedin/s which are reduced in stuations of growth hormone deficit and which remain normal in the presence of growth hormone excess. This has been the reported behavior of the somatomedin known as insulin-like growth factor II (IGF II). The normal somatomedin activity levels found in our acromegalic patients could therefore be explained by a greater sensitivity towards IGF II than towards Sm-C of the bioassay we used.