GROWTH HORMONE (GH) SECRETION AND GH RESPONSE TO GH-RELEASING PEPTIDE 1 (GHRP-1) IN PUERPERAL WOMEN

Abstract

In end-gestational women, pituitary GH secretion and responsiveness to GH-releasing factor are dramatically decreased, possibly due to the abundant presence of placental GH in the maternal circulation (de Zegher et al, JCEM, 1990). As there are no data on postpartum secretion of pituitary GH, it is unknown when pituitary GH secretion recovers. Pituitary GH secretion was evaluated in lactating, puerperal women (n=20; 38-58 h postpartum) and in age-matched, mid-cycle women (n=10, including 3 mothers, 6 months or more after last delivery). Serum GH concentrations were measured at 20 min intervals from 20 min before until 100 min after an IV bolus of either GHRP-I (100 microgram in saline) or saline. Saline-injected puerperal women produced uniformly flattened GH profiles characterized by lower (p<0.01) GH peaks (median 5.6 ng/ml; P10-P90 range : 2.5-6.9 ng/ml) than mid-cycle women (9.1 ng/ml; 8.2-16.5 ng/ml), and higher (p<0.01) GH troughs (2.1 ng/ml; 1.5-2.9 ng/ml) than control women (all undetcctable). The GH response to GHRP-1 in mid-cycle women (88.6 ng/ml; 44-111 ng/ml) was sevenfold higher (p<0.001) than in puerperal women (12.9 ng/ml; 5.0-29.0 ng/ml). Basal serum prolactin concentrations were twentyfold higher in puerperal than in control women, whereas serum IGF-1 concentrations were similar. In conclusion, puerperal women appear to present a distinct pattern of GH secretion and a strikingly low GH responsiveness to GHRP-1, suggesting that the pituitary hyposomatotropism of late gestation persists at least during the first days of puerperium.