To evaluate the effect of t-E2 upon GH response to clonidin stimulus, we studied 61 pré-pubertal children (13 normal; 48 with idiopathic short stature). Classical oral clonidin test was done(0.1mg/m2) after which an adhesive transdermal-E2 system was employed (liberation of 50 μg/day), to the subscapular region. A second clonidin test was performed 72h later and the system removed at the end. Group 1: 13 patients with normal stature (-1< Zscore < +1), CA=6,0 years (+/- 3.0). Patients with short stature (Zscore < -2SD) were divided in subgroups according to the GH peak during the first test; the subgroup 2A had 12 patients with CA=7,0 years (+/- 2,5) showing GH peak <10ng/mL and the subgroup 2B had 36 patients with GH peak>10ng/mL. Mean and standard deviation (SD) were showed in the table:

Table 1
Full size table

Local allergy was seen in 1 case. Gynecomastia did not occur. Estradiol absorption could be detected by the elevation of basal E2 during the second test. There was no difference between basal GH and SmC after t-E2. All groups presented a significant GH peak after t-E2. In group 1, GH peak<10ng/mL was seen in 3/13 (23%) patients during the first test and after t-E2 all of them showed GH peak>10ng/mL. We had 12/48(25%) patients with short stature in which GH peak was under 10ng/mL during the classical clonidin test; only 5 of them maintained this pattern of response after t-E2. Conclusion: the priming with t-E2 increases the GH response to clonidin stimulus and could be useful in patients with short stature reducing the inadequate diagnosis of GH deficiency.