Assessment of growth hormone insulin like growth factor-I axis in Down's syndrome.
As GH therapy has been reported to increase growth velocity in children with Down's syndrome (DS), we studied the GH-IGF-I axis in some DS patients affected by growth retardation without serious congenital malformation, malnutrition or pathological thyroid or adrenal function. IGF-I and IGF-II were evaluated in 39 patients in basal conditions. The patients were subsequently divided into two groups with respect to the IGF-I basal value: Group 1 (GR 1) consisting of patients with abnormally low basal IGF-I concentration as compared to age matched control subjects, group 2 (GR 2) consisting of patients with IGF-I in the normal range. In 6 GR 1 patients and 12 GR 2 patients we evaluated GH and IGF-I concentrations after stimulation with arginine (0.5 g/kg bw), and recombinant GH (4 IU im). In the same patients, GH radioreceptor assay and serum GH-binding protein were evaluated. In all patients IGF-II proved normal (534 +/- 23 ng/ml; mean +/- SE), while IGF-I was pathological in 36% of subjects. The cause of the defective IGF-I secretion in these patients does not seem to depend on an impaired GH axis, as no significant difference in arginine-stimulated GH peak values was seen between GR 1 (29.6 +/- 5.3 ng/ml) and GR 2 (15.1 +/- 2.24 ng/ml). IGF-I concentration evaluated 12, 24, and 48 h after arginine stimulation was significantly increased only in GR 2 patients (peak value: 0.95 +/- 0.1, p = 0.0003 vs baseline; GR 1: 0.34 +/- 0.05 U/ml).(ABSTRACT TRUNCATED AT 250 WORDS)
Barreca
A
A
Dipartimento di Scienze Endocrinologiche e Metaboliche, Università di Genova, Italy.
Rasore Quartino
A
A
Acutis
M S
MS
Ponzani
P
P
Damonte
G
G
Miani
E
E
Balestra
V
V
Giordano
G
G
Minuto
F
F
D002352:Carrier Proteins / Q000032:analysis / Q000097:blood / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D004314:Down Syndrome / Q000097:blood / Q000378:metabolism / Q000503:physiopathology*; D005260:Female; D006130:Growth Disorders / Q000097:blood / Q000378:metabolism / Q000503:physiopathology; D013006:Growth Hormone / Q000032:analysis / Q000097:blood / Q000502:physiology*; D006801:Humans; D007223:Infant; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000502:physiology*; D007335:Insulin-Like Growth Factor II / Q000032:analysis / Q000502:physiology; D008297:Male; D011863:Radioimmunoassay; D011986:Receptors, Somatotropin / Q000032:analysis / Q000502:physiology
D002352:Carrier Proteins; D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D013006:Growth Hormone; C051815:somatotropin-binding protein