Dynamic evaluation of the hypothalamic–pituitary–adrenal and growth hormone axes and metabolic consequences in chronic insomnia; a case–control study

The stimulability and supressibility of hypothalamo-pituitary–adrenal (HPA) axis and stimulability of growth hormone (GH) axis is not known in chronic insomnia (CI). We aimed to examine the effects of CI on HPA and GH axes by dynamic tests, and metabolic consequences. Eighteen CI patients and 14 controls, without any other accompanying sleep and metabolic disorders and drug usage were enrolled into the study. Serum leptin and ghrelin levels were measured at 08:00 a.m. in the fasting state. Salivary cortisol rhythm (06:00, 12:00, 18:00, 24:00) and oral glucose tolerance test (OGTT) were performed on separate days. Low dose (1 µg) ACTH stimulation, glucagon stimulation test (GST), and dexamethasone suppression test (DST) were performed at 08:00 a.m. leaving 48 h in between. Salivary cortisol levels at 18:00 were found to be significantly higher in CI compared to controls (0.14 ± 0.11 vs 0.08 ± 0.06, respectively; p = 0.027). Basal, peak and area under curve of cortisol responses to dynamic stimulation tests were similar in two groups. Cortisol levels after overnight DST were also similar in two groups. GH responses to GST were not different between groups. Fasting glucose levels, HOMA-IR, OGTT and lipid levels were similar in both groups. The insomnia group had similar leptin and ghrelin levels compared to the control group. Our results indicate that, although CI is associated with elevated evening salivary cortisol levels, neither dynamic feedback regulation of the HPA and GH axis nor leptin and ghrelin levels are affected.