Pulsatile secretion pattern of growth hormone in turkeys: effects of age and sex

Male and female turkeys were cannulated through the jugular vein, and blood samples were withdrawn remotely at 10-min intervals for a period of 8 hr at two points in the post-hatch growth phase (4 and 14 weeks of age). Growth hormone (GH) concentration was determined for each sample by radioimmunoassay using a recombinant chicken growth hormone preparation as standard. Data were evaluated for age- and sex-related differences. Four-week-old male and female turkeys displayed a pulsatile pattern of GH secretion. Growth hormone secretory profile characteristics differed significantly between ages with regard to overall mean, number of peaks, amplitude of peaks, interval between peaks, baseline, and total GH detected. Male four-week-old turkeys had a peak amplitude significantly greater than that of females of the same age. Older (14-week-old) male turkeys demonstrated a significantly greater number of GH secretory peaks than females during the 8-hr sampling period; however, overall it did not appear that the older birds had an organized pattern of GH secretion above baseline levels.