Search

This study concerns the immunoreactive somatomedin C secretion by prepubertal rabbit epiphyseal chondrocytes cultured in a defined serum-free medium. In such culture conditions, chondrocytes mainly synthesized Type II collagen (80% of total collagen) during 10 days. A small amount of Type I collagen was also found with a significant (p less than 0.05) higher level during the period of cell multiplication (6.4 +/- 1.5%) than when cells reached confluency (0.9 +/- 0.2%). During the 10 days of culture without serum and without hormone added, a Sm-C/IGF1 activity was measured by RIA at a mean level of 30 +/- 5 mU/ml/10 micrograms DNA. This value was significantly higher (p less than 0.001) than in the medium not incubated with the cells (1.7 +/- 0.9 mU/ml). When hGH was added to the culture medium during the period of cell division, the level of Sm-C/IGF1 activity was significantly elevated at 39 +/- 4 mU/ml/10 micrograms DNA (p less than 0.05) and at 55 +/- 3 mU/ml/10 micrograms DNA (p less than 0.001) with 50 ng/ml and 100 ng/ml hGH concentrations respectively. On the contrary, no difference was observed at confluency in treated and non treated cells.

Anorexia nervosa in childhood and adolescence, associated with impaired growth can be considered as a form of chronic malnutrition. Twelve patients aged 11 to 17 years were investigated. In spite of increased GH secretion, plasma somatomedin activities were diminished in 8 cases. Plasma T4, T3 and arginine stimulated insulin secretion were also decreased. In six patients who gained weight a significant negative correlation was found between weight deficit and plasma somatomedin activity. Prolonged administration of growth hormone in one case did not stimulate the generation of somatomedin activity. Nutrition and increased insulin secretion could plan a role in changes observed during recovery.

In a large group of 74 patients irradiated with 2400 rad for acute lymphoblastic leukemia an unusually high frequency of complete GH deficiency was observed (40%). Only 11 out of 46 prepubertal children had growth retardation and seven children received hGH treatment. On the contrary 11 other prepubertal cases had normal growth rates in spite of lack of response to AITT. Plasma SmC values were correlated with growth rates but were discrepant with GH responses to AITT in some cases. Because of this high frequency of GH dysregulation further growth at time of puberty should be carefully documented.

Somatomedin activity, as estimated by the porcine bioassay and GH response to stimulation were compared in prepubertal children with severe growth retardation and lack of evidence of pituitary dysfunction. Somatomedin activity was strongly correlated with growth rate. A group of patients had a low somatomedin activity in contrast with normal GH responsiveness. This appears to be a rather frequent situation and deserves further evaluation of the somatomedin system and a more critical approach of GH secretion.

This study was undertaken to investigate the role of GH secretion in the pubertal increase in plasma somatomedin-C (Sm-C) concentrations and its relation to growth in children with true precocious puberty (PP) and normal or deficient GH secretion. We studied 37 children (9 boys and 28 girls), divided into 3 groups according to their pubertal stages and their peak stimulated plasma GH concentration. Group I (n = 20) contained patients with PP and normal GH secretion. In group II (n = 8), PP was accompanied by GH deficiency. Group III (n = 9) patients were GH deficient and prepubertal. The mean plasma Sm-C (RIA) levels in groups I and II were 2.01 +/- 0.17 (+/- SEM) and 0.59 +/- 0.21 U/mL, respectively (P less than 0.001), and it was 0.09 +/- 0.01 U/mL in group III (P less than 0.001 compared to group II). The higher mean plasma Sm-C level in group II compared to that in group III could be related to a significantly higher GH response to arginine-insulin stimulation (P less than 0.02), although this value was in the hypopituitary range. The mean growth rate in group II (6.8 +/- 0.9 cm/yr) was also much higher than the rate in group III (1.9 +/- 0.5 cm/yr; P less than 0.001) and only slightly lower than that in group I (90 +/- 0.8 cm/yr; P less than 0.05). These data indicate that plasma Sm-C values are closely correlated with even small changes in GH secretion. The observed growth rates could, in general, be linked to plasma GH and Sm-C levels, as modulated by sex steroids, in these patients with precocious puberty.