Growth hormone (GH) responses to GRF (1 microgram/kg BW i.v.) were investigated. Comparison between GRF(1-40) and GRF(1-29)NH2 in 11 young adult volunteers gave identical results. One hundred and thirty-one children and adolescents (45 with idiopathic GHD) were tested with GRF (1-29)NH2. The maximal GH levels (max GH) in response to GRF during the 120 min test period were found suitable to characterize the response. In cases without GHD no correlation to age, sex and pubertal development was observed. A maximal GH level of above 10 ng/ml was found to be normal. In 3 out of 86 children without GHD (one with Turner syndrome; two with simple obesity) max GH fell short of 10 ng/ml, while 11 of 45 cases with GHD exceeded this margin. In GHD, max GH was inversely correlated with age. There was no difference in max GH between groups with or without perinatal pathology as a presumed cause of GHD. GH levels to GRF were positively correlated with maximal GH level during sleep in GHD, but not correlated with responses seen to insulin or arginine. The value of GRF testing for the confirmation of GHD is discussed in the light of other GH stimulatory tests and basal somatomedin C measurements. It is suggested that the combination of testing with GRF and the determination of a basal SmC level offers a safe and convenient way to diagnose GHD in clinically suspected cases, though in some cases further diagnostic tests may be needed.

Department o f P e d i a t r i c s , U n i v e r s i t y of Bologna. I t a l y . GH-RF d e f i c i e n t c h i l d r e n (1 u i t h i s o l a t e d GH-deficiency, 2 u i t h GH-TSH d e f i c i e n c i e s , 1 u i t h GH-TSH-ACTH-deficiencies) u e r e a d m i n i s t e r e d 5.c. hGH ( a f t e r t h e p r e v i o u s hGH t r e a t m e n t had been d i s c o n t i n u e d 1 week before the s t u d y ) a t a dose o f 0.1 UI/Kg. according t o u s u a l s u b s t i t u t i v e therapy. a t t i m e s 0 and 48 h. A f t e r a f u r t h e r week n i t h o u t t h e r a p y the s u b j e c t s u e r e a d m i n i s t e r e d i . v . GH-RF a t a dose o f 3 )g/Kg a t t i m e s 0,8.16.24,32.40.48.56,64 h . SmC b l o o d samples u e r e c o l l e c t e d a t time 0 and, a f t e r hGH and GH-RF a d m i n i s t r a t i o n s , a t t i m e s4. 8,12.16.24,28,32,36,40,48,52,56.50,64,72 h. I n a l l p a t i e n t s a s i g n i f i c a n t GH-response ( 4 n g / a l ) uas a t t a i n e d a f t e r each GH-RF a d m i n i s t r a t i o n . I n 3 s u b j e c t s a SnC i n c r e a s e was observed a f t e r both hGH and GH-RF a d m i n i s t r a t i o n s .I n 1 case t h e r e u e r e no changes i n SnC l e v e l s a f t e r both hGH and GH-RF a d m i n i s t r a t i o n s . By c a l c u l a t i n g the i n t e g r a t e d areas of the SmC curve. t h e values o b t a i n e d a f t e r hGH and GH-RF a d m i n i s t r a t i o n s u e r e h i g h e r i n 2 cases a f t e r t h e GH-RF i n j e c t i o n . h i g h e r i n 1 case a f t e r the hGH i n j e c t i o n , and i n 1 case t h e areas were s i m i l a r . I n our p a t i e n t s and i n our experimental -So far 51 children were tested in an identical mode. In the 32 cases classified as non-3 deficient all GH levels rose to more than 8 ng/ml (1. IRP) above basal with trends according to sex and age. In 19 cases GHD had been established by testing with insulln and arginine, and Sm measurements. In these patients GH increments were: <3 ng/ml in 10, 3-5 ng/ml in 6, and >9 ng/ml (14.6, 9.1, 35.8) in 3 cases. Thus, GRF(~-29) is suitable for GH testing. Easier synthesis rakes it also appear to be a favourable alternative for attempts to treat hypothalamic gravth hormone deficiency. he^ long term effect of-daily injeGions of GFS (1 ug/kg bw,sc) was studied in developing male rats.In t w~ additional groups GRF was stopped on day 30 and on day 50.Weight and length were m asured at 5 days intervals,GH and somtomedin =re ~asured at diverse t W pints by RIA.When cqared to the controls,GRF treated animals did not differ in length at the end of the observation pericd(day 75) .On the other hand,the growth pattern was markedly different.GRF treated animals grew faster f r m day 15 to day 25,and had significantly lower GH levels than the controls on day 30 (3.05 vs 23.0112 ng/ml,p