Somatostatin infusion suppresses GH secretory burst frequency and mass in normal men

In attempting to elucidate the neuroendocrine mechanisms that regulate pulsatile growth hormone (GH) secretion, we measured serum GH concentrations by an ultrasensitive immunofluorometric method in blood collected every 10 min for 8 h in 11 young healthy male volunteers (age range 21-31 yr) before and during somatostatin (SS) administration (an iv bolus dose of 350 μg followed by a continuous infusion at the rate of 6 μg · kg^-1 · h^-1, which increases the circulating SS levels to ~570 μg/ml). Pulsatile GH secretion was analyzed using the computer-assisted pulse detection program cluster method and deconvolution analysis. The area and frequency of GH peaks were significantly reduced during SS infusion compared with basal values, but detectable pulsatile episodes were still present. These data suggest that, in adult males, SS controls pulsatile GH secretion and can decrease the mass and frequency of GH secretory bursts.