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To characterize the serum growth promoting activity estimated by means of bioassay (Thymidine Activity), the gel filtration chromatographic profile of sera obtained from 10 normal adults and from 10 normal infants was performed. For each serum fraction we evaluated the capacity to stimulate the tritiated thymidine (3H-TdR) uptake into lectin-activated lymphocytes. This capacity was expressed as percent increase in 3H-TdR uptake in presence and in absence of the optimal dose (1.25%) of the fraction. The highest percent increase in 3H-TdR uptake was obtained in the same three fractions (1500-2500 Kd, 28-42 Kd, 1.3-1.9 Kd) in the sera of adults as well as infants. The values observed in infants were higher than in adults, suggesting that the serum growth-promoting activity could be higher in rapidly growing subjects.

Gonadal impairment has been observed in patients who underwent bone marrow transplantation with TBI-containing cytoreductive regimen. In order to study the effects of radiations on the pituitary and gonadal hormones 12-18 months after transplantation sexual development and plasma levels of gonadotropins, estradiol, and testosterone were evaluated in 9 patients (4 boys and 5 girls, age range 11-20 years). The preliminary results of this study show that TBI produces in both sexes a gonadal impairment, as shown by the high plasma levels of gonadotropins. Nevertheless, the gonadal damage seems to be more important in girls and we suppose a greater sensitivity to radiation injury of the ovary than of the testis.

Eight GH-deficient children were treated with GHRH (1-44), once daily s.c. for 6-18 months. At the 6th month of therapy, 3 patients showed a catch-up growth ("responders"), while the remaining 5 did not ("non-responders"). In all patients treatment was discontinued after 6-18 months, when its effect on growth rate failed. After a wash out period of at least 6 months, patients were submitted to biosynthetic GH therapy. After 6 months of GH treatment a significant catch-up growth was found in both responder and non-responder children. GHRH therapy is found to be less effective than GH treatment. Other methods of GHRH administration are worth investigating.

We previously reported that natural cytotoxicity, mediated by Natural Killer (NK) cells, is low in GH-deficient children and increases up to normal levels after a long-term treatment. In order to investigate the role of GH and IGF1 on the restoration of this immune function, we studied the in vitro effect of increasing doses of biosynthetic GH and IGF1 on NK activity of GH-deficient children. No variations of NK activity were observed after incubation of GH-deficient children's cells in the presence of GH as well as IGF1. Our data suggest the effect of GH and IGF1 on NK activity not to be direct, but mediated by unidentified factors.