PLASMA GH RESPONSES TO GHRH, ARGININE, L-DOPA, PYRIDOSTIGMINE, SEQUENTIAL ADMINISTRATIONS OF GHRH AND COMBINED ADMINISTRATION OF PD AND GHRH IN TURNERS-SYNDROME

To investigate GH secretory capacities in patients with Turner's syndr ome, GHRH, arginine, L-dopa and pyridostigmine (PD) were administered singly and GHRH was administered sequentially for 3 days. In addition, plasma GH and TSH responses to GHRH and TRH after pretreatment with P D were analyzed to investigate whether the hypothalamic cholinergic so matostatinergic system functioned normally. The maximal GH responses t o GHRH, L-dopa and PD were significantly smaller in Turner's syndrome (no.=14) than in normal short children (NSC, no.=14). However, there w as no difference in plasma GH responses to arginine between the two gr oups. In ten patients with Turner's syndrome, the plasma GH response t o GHRH did not improve even after the sequential 3-day administrations . Although plasma GH and TSH responses to GHRH and TRH were significan tly enhanced by the pretreatment of PD in NSC (no.=12), these response s were not enhanced in Turner's syndrome. Plasma GH response to GHRH i n Turner's syndrome with normal body fat was still significantly lower than in NSC. It is therefore concluded that somatotroph sensitivity t o GHRH is decreased in Turner's syndrome and that this may be due to t he primary defects of the somatotrophs rather than to the increased bo dy fat. In addition, the network of cholinergic-somatostatinergic syst ems seemed to be impaired in these patients, while the activity of hyp othalamic somatostatin neurons was thought to be maintained. (C) 1998, Editrice Kurtis.