GH secretion reserve in subclinical hypercortisolism.

PURPOSE: In overt hypercortisolism, growth hormone (GH) secretion is decreased and normalizes after surgery. In subclinical hypercortisolism (SH), GH secretion has been scarcely investigated. We assessed GH reserve in patients with and without SH and, in the former, also after recovery.
METHODS: We enrolled 24 patients with adrenal adenomas, 12 with SH (SH+, 8 females, 58.3 ± 6.5 years) and 12 without SH (SH-; 11 females, 61.8 ± 10.6 years). SH was diagnosed in the presence of ≥ 2 out of: 1 mg overnight dexamethasone suppression test >83 nmol/L, urinary free cortisol (UFC) >193 nmol/day and ACTH levels <2.2 pmol/L. GH secretion was assessed by GHRH + Arginine test (GHRH-ARG) and age-adjusted serum IGF-I levels, expressed as SDS (IGF-I SDS). Eight SH+ patients were re-evaluated after the recovery from SH.
RESULTS: Age, gender, body mass index (BMI) and IGF-I SDS were comparable between SH+ and SH- patients. After GHRH-ARG the mean GH peak levels (GH-P) and GH response (as Area Under Curve, GH-AUC) were lower in SH+ than in SH- patients (15.2 ± 8.1 vs 44.5 ± 30.9 μg/L, P = 0.004 and 1,418 ± 803 vs 4,028 ± 2,476 μg/L/120 min, P = 0.002, respectively), after adjusting for age and BMI. The GH-AUC and GH-P levels were negatively associated with UFC after adjusting for age and BMI (β = -0.39, P = 0.02 and β = -0.4, P = 0.020 respectively). After recovery, GH-P levels and GH-AUC increased as compared to baseline (23.7 ± 16.3 vs 15.8 ± 10.2 μg/L, P = 0.036 and 2,549 ± 1,982 vs 1,618 ± 911 μg/L/120 min, P = 0.012, respectively).
CONCLUSIONS: GH secretion reserve is decreased in SH patients and increases after the recovery.