Enhanced activity of the pituitary-gonadal axis in premature human infants.

The postnatal pituitary-gonadal function of fullterm and premature boys and girls (mean gestational age, 40 and 32 weeks, respectively) was studied by measurements of serum FSH, LH, PRL, and testosterone (T) between 0-25 weeks of postnatal age. During the first 10 postnatal weeks, serum FSH in premature girls reached 10-20 times higher levels than in fullterm girls (mean at 1-5 weeks, 63 and 3.9 mIU/ml, respectively; P < 1.001). During the same time, serum LH levels were 3-4 times higher in premature (12-17 mIU/ml) than in fullterm girls (3.8-4.7 mIU/ml; P < 0.01). In contrast, no difference in serum gonadotropin levels were observed between premature and fullterm boys. Serum T in premature boys (mean, 2.95 ng/ml) reached a significantly higher level (P < 0.01) than in fullterm boys (1.45 ng/ml) from 11-15 weeks of age. The results emphasize the importance of the last weeks of gestation for the functional maturation of the fetal hypothalamic-pituitary-gonadal axis. Interruption of this maturational process by premature birth results in enhanced pituitary gonadotropin production in girls and increased testicular T production in boys.