Gender differences in diurnal growth hormone and epinephrine values in young adults during ambulation.

BACKGROUND In the present study, the impact of gender, oral contraceptives, and ambulation on serum growth hormone (GH) and urinary catecholamines was examined in healthy young adults. METHODS Twenty-one medical student volunteers--7 men, 7 women, and 7 women taking oral contraceptives--were investigated. Serum samples were drawn every second hour during a 24-h period. At 0800 the first morning, serum samples were drawn while subjects were in the ambulatory state; the next morning, serum samples were drawn at 0800 while the subjects were still resting in bed. RESULTS During the daytime, GH concentrations were sevenfold higher in the women than in the men, a difference larger than described previously. During the night, there was no gender difference. In the morning, ambulatory GH concentrations were 28-fold higher in the women than in the men, whereas supine GH concentrations were only 4.6-fold higher in the women than in the men. Daytime urinary output of epinephrine was lower in the women than in the men, whereas there was no difference at night. Women using estrogen-containing oral contraceptives had lower epinephrine and higher GH values than women not taking oral contraceptives. In women, morning GH concentrations were higher in the ambulatory than in the resting state, whereas they were lower in the ambulatory state than in the resting state in men. CONCLUSIONS The secretion of GH and epinephrine is gender-dependent and differs during the daytime in a reciprocal manner, with higher GH and lower epinephrine in women than in men. Oral contraceptives appear to further increase such differences. It seems likely that the data reflect a gender difference in the utilization of substrates for energy production.