Somatomedin in cystic fibrosis.

Abstract

A The growth promoting effect of growth hormone is known to be mediated via somatomedins, a group of peptides produced mainly by the liver. A change in hepatic function or systemic forces which especially modify the formation of somatomedin by the liver, lower the somatomedin levels. The latter results in increased secretion of growth hormone presumably via feedback mechanisms ( I ) . The following studies were performed to evaluate somatomedin activity in patients suffering from cystic fibrosis (CF), knowing that in this disease growth failure, malnutrition and hepatic involvement are common features. Nineteen CF-patients with typical pulmonary and pancreatic symptoms were compared with 41 healthy children with normal development, height and weight. At the time studied the CF-patients were all clinically stable without signs of diabetes or hepatic involvement. The age distribution was equal for C F and normals (N: 155f26 months-CF: 156f29 months ( X f 2 SD)). All samples were obtained between 9 and 10 a.m. and promptly centrifuged and stored at -8OC until assayed. A modified analysis of sulphate incorporation in the pelvic cartilage of 12-day-old chick embryos was utilized (2). In spite of improved management of pulmonary and pancreatic complications in CF, retardation of skeletal growth is still a common manifestation of the disease (3), reported not to be confined to those with severe malabsorbtion or lung complications (4). The growth hormone levels have been reported normal or elevated (549, and other hormones influencing the growth and growth spurt have been reported normal including, thyroid hormones and gonadal and adrenal steroids (9-13). Recently two separate somatomedin studies have been reported (7, 14). By using bioassay in six patients with C F Lee et al. (14) demonstrated reduction of somatomedin activity to about 50% of values in normal children. The opposite result was obtained by Rosenfeld et al. (7), using placental membrane radioreceptor assay in measuring total somatomedin peptide content in plasma of 15 C F patients. The conflicting results have been discussed by the latter group. The presence of a circulating somatomedin inhibitor, whose existence might be secondary to either malnutrition or to an underlying metabolic defect in CF, is mentioned. Our results, showing normal somatomedin activity in C F patients (Fig. I ) , using a welldocumented bioassay (2), are however similar to the results presented by Rosenfeld et al. (7), suggesting normal generation of normally