Authors: Antonina Barreca A Rasore Quartino M S Acutis P Ponzani G Damonte E Miani V Balestra G Giordano F Minuto
Publish Date: 2014/04/02
Volume: 17, Issue: 6, Pages: 431-436
Abstract
As GH therapy has been reported to increase growth velocity in children with Down’s syndrome DS we studied the GHIGFI axis in some DS patients affected by growth retardation without serious congenital malformation malnutrition or pathological thyroid or adrenal function IGFI and IGFII were evaluated in 39 patients in basal conditions The patients were subsequently divided into two groups with respect to the IGFI basal value Group 1 GR 1 consisting of patients with abnormally low basal IGFI concentration as compared to age matched control subjects group 2 GR 2 consisting of patients with IGFI in the normal range In 6 GR 1 patients and 12 GR 2 patients we evaluated GH and IGFI concentrations after stimulation with arginine 05 g/kg bw and recombinant GH 4 IU im In the same patients GH radioreceptor assay and serum GHbinding protein were evaluated In all patients IGFII proved normal 534±23 ng/ml mean±SE while IGFI was pathological in 36 of subjects The cause of the defective IGFI secretion in these patients does not seem to depend on an impaired GH axis as no significant difference in argininestimulated GH peak values was seen between GR 1 296±53 ng/ml and GR 2 151±224 ng/ml IGFI concentration evaluated 12 24 and 48 h after arginine stimulation was significantly increased only in GR 2 patients peak value 095±01 p=00003 vs baseline GR 1 034±005 U/ml By contrast administration of GH produced a rise in IGFI in both groups though the mean peak value in GR 1 063±009 U/ml p=00005 vs baseline was lower than that in GR 2 107±01 the size of the increase in relation to the baseline values was similar in both groups GR 1 173±29 GR 2 87±16 In agreement with these findings we have indirectly proved the presence of GH receptor in the GR 1 patients and demonstrated their normal levels by evaluating the GHbinding protein DS 215±68 Bound/Total controls 236±118 On the other hand the evaluation of the GH RRA/IRMA ratio revealed a presence of a reduced bioactivity of endogenous GH in GR 1 081±01 GR 2 105±006 and particularly in two patients 041 and 061 respectively In conclusion our data suggest that impaired growth in some patients affected by Down’s syndrome can be accounted for by a GH molecule that is immunoreactive but not bioactive
Keywords: