Abstract
A competitive protein-binding assay has been developed using: 1) a rat liver protein which proved specifically to bind somatomedins (SM) and 2) 125I NSILA-S*as tracer and NSILA-S*(4.5mU/mg) as standard. NSILA-S, SM-A**and serum SM extracted by acidic gel filtration gave parallel displacement curves. Results are expressed in relation to a standard pool of serum from normal adult males arbitrarly assigned a value of 1 U/ml SM.
11 adults and 7 children with Cushing's syndrome were studied. In untreated patients, the mean ± SEM levels (0.85 ± 0.07 U/ml, n=15)were not significantly different from those of normal adults (1.07±0.1,n=9). The cortisol levels were 20.9±2.7 μg/100ml (normal 10 ± 0.5). In the 7 children whose mean growth rate was 1.4 cm/year, SM levels (0.86±0.12 U/ml) were significantly higher (p< 0.001) than those in 8 hypopituitary dwarfs of the same age (0.21±0.05). In 10 treated patients, the mean SM levels were 1.04±0.11 U/ml and the cortisol levels 4.7 ± 1.6 μg/ml.
In 6 untreated patients, SM activity was determined by the chick embryo assay. Mean levels (0.72±0.06 U/ml) were below normal (p∽0.05). The results would suggest that the growth arrest in Cushing's syndrome is not a consequence of impaired SM synthesis.
*gifts from Dr Zapf (Zürich). ** gift from Dr Fryklund (AB Kabi, Stockholm).
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Gourmelen, M., Girard, F. & Binoux, M. Determination of serum somatomedin levels in patients with Cushing's syndrome by competitive protein-binding assay. Pediatr Res 13, 1191 (1979). https://doi.org/10.1203/00006450-197910000-00063
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DOI: https://doi.org/10.1203/00006450-197910000-00063