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 wa s 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 ever y second hour during a 24-h period. At 0800 the first morning, serum sample s 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. Duri ng 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 s upine 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 t he men, whereas there was no difference at night. Women using estrogen-cont aining oral contraceptives had lower epinephrine and higher GH values than women not taking oral contraceptives. In women, morning GH concentrations w ere higher in the ambulatory than in the resting state, whereas they were l ower in the ambulatory state than in the resting state in men. Conclusions: The secretion of GH and epinephrine is gender-dependent and di ffers during the daytime in a reciprocal manner, with higher GH and lower e pinephrine in women than in men. Oral contraceptives appear to further incr ease such differences. It seems likely that the data reflect a gender diffe rence in the utilization of substrates for energy production. (C) 1999 Amer ican Association for Clinical Chemistry.