Background: Some studies have demonstrated that the function of the growth hormone (GH)-insulin-like growth factor (IGF)-1 axis is significantly impaired in patients with oral corticosteroid (CS)-induced osteoporosis. The aim of study was to investigate the effects of long-term therapy with inhaled CSs (ICSs) on the hypothalamic-pituitary-GH axis by the GH response to GH-releasing hormone (GHRH), as well as bone turnover, in adult asthmatic patients.
Design: Cross-sectional study.
Patients: Twenty-seven adult subjects with mild-to-moderate persistent asthma (long-term ICS therapy [ie, > 1 year], 20 patients; naive to ICS treatment, 7 patients) and 10 control subjects.
Measurements: Each subject underwent testing with an IV bolus (1 μg/kg) injection of human GHRH, and samples of GH were taken 15 min before the GHRH injection, at 0 min (ie, at the time of GHRH injection), and at 15, 30, 45, 60, and 90 min after injection to obtain values for peak GH and ΔGH. At baseline, samples of serum IGF-1 and blood-urine were collected for bone turnover markers.
Results: The GH response to GHRH was significantly reduced in asthmatic patients receiving ICSs (peak GH, p < 0.05; and ΔGH, p < 0.01) in comparison with control subjects and asthmatic patients who were naive to ICS therapy (peak GH and ΔGH, p < 0.01). Baseline IGF-1 levels were similar in the three groups. Serum osteocalcin, a marker of bone formation, was significantly reduced (p < 0.01) and correlated with GH peak (r2 = 0.34; p = 0.007) in asthmatic patients who were treated with ICSs.
Conclusions: We conclude that GH secretion in response to GHRH is significantly reduced in adult asthmatic patients receiving therapy with ICS and that such inhibition could play a negative role in bone metabolism.