Low growth hormone response to growth hormone-releasing hormone in child depression.

Background: This study examined growth hormone (GH) response to growth hormone-releasing hormone (GHRH) in a large sample of depressed children compared with normal control children. Within-subject comparisons were also performed in control subjects to examine test-retest reliability and in depressed children comparing episode versus clinical recovery.

Methods: The sample included depressed children (n = 82) and normal control children (n = 55) group-matched for age, gender, and pubertal status; the mean ages were 11.2 +/- 1.7 and 11.2 +/- 1.8 years, respectively. We gave GHRH (0.1 mcg/Kg) at 9 AM, and serum GH levels were determined every 15 min from -30 min through +90 min of the GHRH infusion. A subgroup of normal control subjects (n = 11) repeated the protocol for test-retest reliability within a 2-month interval. A subgroup of depressed children (n = 20) were restudied off all medications following full clinical remission from depression.

Results: The mean GH response to GHRH was significantly lower in the depressed group (8.7 ng/mL +/- SEM 0.9) compared with normal control children [12.2 ng/mL +/- SEM 1.3; t(135) = 2.59, p =.01 effect size 0.44]. The test-retest reliability of GH response to GHRH was stable (intraclass correlation =.93 for mean post-GH). The GH response to GHRH remained low in subjects restudied during clinical remission from depression.

Conclusions: Depressed children show low GH response to GHRH. The measure appears to be reliable, and the low GH response continues following clinical remission. Further studies are needed to explore the mechanism and relative specificity of this finding.