Intravenous administration of recombinant IGF-I lowers serum GHRH and TSH.
Recombinant IGF-I was administered as an iv bolus of 75 micrograms/kg to 10 patients with Laron type dwarfism (3 children aged 9, 11 and 12 years and 7 adults aged 30.6 +/- 3.5 years) and to 8 healthy subjects (mean age 19.9 +/- 12.1 years) and determinations of IGF-I, GHRH, hGH, TSH, and glucose were made before and at 2, 5, 15, 30, 60, 90, and 120 min. The following effects were observed: a. an immediate, marked and sustained drop in blood glucose (p less than 0.001), more prolonged in the patients; b. in both groups, a dramatic rise in plasma hGH (p less than 0.01) which peaked at 60-90 min; in the patients this occurred after an initial immediate fall in plasma hGH (p less than 0.01); c. a progressive decrease of plasma GHRH and TSH (p less than 0.05, 0.02) in both patients and healthy controls. An hypothesis is put forward that acute and time-limited release of somatostatin by IGF-I is the main cause of the hormonal changes registered. As the IGF-I bolus also suppressed circulating insulin levels, the hypoglycemia is considered to be a direct effect of IGF-I.
Laron
Z
Z
Institute of Pediatric and Adolescent Endocrinology, Beilinson Medical Centre, Petah Tikva, Israel.
Klinger
B
B
Silbergeld
A
A
Lewin
R
R
Erster
B
B
Gil-Ad
I
I
D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D002648:Child; D004392:Dwarfism / Q000378:metabolism*; D005260:Female; D013006:Growth Hormone / Q000096:biosynthesis / Q000378:metabolism; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism*; D006801:Humans; D007275:Injections, Intravenous; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008297:Male; D011994:Recombinant Proteins / Q000494:pharmacology; D013972:Thyrotropin / Q000378:metabolism*
D001786:Blood Glucose; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D013972:Thyrotropin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone