Is testosterone and estrogen priming prior to clonidine useful in the evaluation of the growth hormone status of short peripubertal children?

AIM

To determine the usefulness of priming with gonadal steroids prior to growth hormone (GH) stimulation with clonidine in the evaluation of the GH status of short peripubertal children.

CHILDREN AND METHODS

Thirty-nine children, eight females and 31 males, were studied, with a mean chronological age of 12.37 +/- 2.24 years (range 8-15 years), mean bone age 9.58 +/- 2.21 years, Tanner stage 1-2, with height 134.12 +/- 11.27 cm (Ht-SDS -2.24 +/- 0.95), growth velocity (GV) 4.2 cm/yr (GV SDS -2.12 +/- 1.32) and an inadequate response to an initial GH stimulation test with clonidine (peak GH <10 microg/l). A second stimulation test with clonidine was performed in the same patients after gonadal steroid priming: 100 mg i.m. testosterone enanthate 5-8 days prior to GH stimulation in the males, and 1 mg estradiol valerate daily for 3 days in the females. GH, IGF-I, and testosterone/estradiol were measured before and after priming.

RESULTS

Twenty-one of 39 children (53.8%) increased their GH response to a level of >10 microg/l following priming with gonadal steroids. Mean peak GH after priming was 12.32 +/- 8.7 microg/l compared to a peak GH level of 4.87 +/- 2.72 microg/l prior to gonadal steroid priming (peak GH 17.42 +/- 8.46 microg/l in the responders versus 5.95 +/- 2.76 microg/l in the non-responders). Although a significant increase in GH and IGF-I concentrations was noted following priming, we were unable to find a correlation between IGF-I concentrations and peak GH following priming. IGF-I levels were not different in the responders and non-responders to clonidine following priming. There was no correlation between pubertal staging and testosterone/estradiol concentrations before priming with the peak GH after priming.

CONCLUSIONS

Priming with gonadal steroids significantly improves GH secretion following GH stimulation with clonidine and diminishes the possibility of a false diagnosis of GH deficiency. Gonadal steroid priming should therefore be considered in the evaluation of the GH status of short children close to or during the early stages of puberty.