Comparison of Stimulated Growth Hormone Levels in Primed versus Unprimed Provocative Tests

Abstract

Objective: To show the importance of priming prior to growth hormone (GH) stimulation tests in the diagnosis of GH deficiency, the effect of different doses and schedules of testosterone (T) on GH levels. Patients and Methods: Eighty-four prepubertal and early pubertal boys whose heights were 2 SD below the mean and height velocities <4 cm per year and who failed in GH stimulation tests were included in the study. The boys were divided into two groups: the first group consisting of 41 boys was primed with 62.5 mg/m² (low dose testosterone – LDT) and the second group consisting of 43 boys with 125 mg/m² depot testosterone (conventional dose testosterone – CDT) intramuscularly 1 week before the stimulation test. Twenty-one boys out of 36 who failed in GH stimulation tests after one dose T injection were treated with three doses of 62.5 mg/m² T (multiple dose testosterone – MDT) injections monthly and retested. Results: The GH levels increased from 4.80 ± 2.78 to 11.50 ± 8.84 ng/ml and from 4.76 ± 2.46 to 12.98 ± 8.30 ng/ml by priming with LDT and CDT respectively. The increment of mean GH levels by both LDT and CDT were found to be similar (p = 0.443). The peak GH levels were found to be elevated >10 ng/ml in 22/41 (54%) and 26/43 (60%) who received LDT and CDT respectively (p = 0.528). The mean GH level of 21 boys who received MDT was increased from 5.38 ± 2.50 ng/ml (by priming with one dose T) to 10.19 ± 6.13 ng/ml (p = 0.004). Twelve (57%) of 21 boys who received MDT responded to GH stimulation test >10 ng/ml. The T level increased from 0.71 ± 0.97 to 4.54 ± 2.80 ng/ml by LDT (p < 0.001) and from 0.65 ± 0.71 to 7.18 ± 3.18 ng/ml by CDT (p < 0.001). The increment of T level was higher by CDT than LDT (p = 0.001). There was no correlation between T and peak GH levels after priming. Conclusion: LDT is as effective as CDT in priming of GH stimulation tests. The ones who failed in GH stimulation tests after one dose T injection can be primed with MDT. The stimulated GH level after priming was related neither to the plasma level of T nor the dose of T.