Impairment of Growth Hormone Secretion in Response to Hypoglycemia During Early and Late Pregnancy

In order to ascertain whether the diminished pituitary growth hormone (HGH) response observed in late pregnancy may be quantitatively related to the duration of gestation, sequential studies in the HGH responses to insulin-induced hypoglycemia were made during each trimester of pregnancy and at 6–7 weeks post partum in 10 non-obese subjects. The HGH responsiveness to hypoglycemia was progressively diminished during the 3 trimesters and became blunted during the last trimester of pregnancy when compared with their own postpartum controls. Normal brisk HGH response to hypoglycemia was observed at 6–7 weeks post partum. Although the presence of a large quantity of circulating human placental lactogen may account for the inhibitory effect on the hypothalamic-pituitary HGH releasing mechanism in late pregnancy, other hormonal factors such as elevated progesterone and nonprotein-bound cortisol may play a role in the suppressive effect on HGH release during early pregnancy.