Growth hormone and somatomedin-C response to synthetic human pancreatic tumor GH-releasing factor in hypopituitary and constitutionally short children

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Abstract
GH and somatomedin-C response to acute hpGRF-44 iv administration (1 μg/ Kg bw) was studied in 16 patients with hypopituitarism (GHD) and in 7 constitutionally short subjects. GH-deficient patients evidenced a significant GH increase peaking between 15 and 60 min. (4.95 ± 0.88 ng/ml, mean ± SE) (p < 0.01 vs placebo). In non GH-deficient subjects GH increase was more pronounced (peak 18.00 ± 3.01 ng/ml; p< 0.01 vs both placebo and GHD group). Acid-extractable somatomedin-C was slightly, but significantly higher than baseline at 12th h (p < 0.01) in both patients with hypopituitarism (basal value: 0.067 ± 0.021 U/ml; 12 h: 0.096 ±0.024 U/ml) and constitutionally short subjects (basal value 0.62 ± 0.13; 12h 0.72 ± 0.16 U/ml). In 3 subjects with hypopituitarism multiple iv administrations (1 μg/kg bw at 09:30 and 21:30 h for 4 days) produced on the average a modest increase of the GH responsiveness, were more effective to enhance somatomedin-C concentration, but not sufficient to reach normal levels. Sc administration of the same dose at 4-h intervals by a programmable portable pump — performed on 6 GHD subjects — produced an increase of GH peak response on the 4th day of treatment (1.38 ± 0.31 ng/ml) with respect to the one observed on the first day (0.42 ± 0.09 ng/ml). Somatomedin-C increase was low and inconstant. These data support the use of a 4–5-day pulsatile treatment in the differentiation between hypothalamic and pituitary deficiency, and the possibility of therapeutical use of GRF with the same protocol when a response is evidenced.