Increased activity of the hypothalamic-pituitary-testicular axis in infancy results in increased androgen action in premature boys.

Context: Transient activation of the hypothalamic-pituitary-gonadal (HPG) axis is observed in boys during the first months of life. Previous research suggests increased HPG axis activation in premature infants, but the physiological significance of this has not been studied. Objective: The objective of this study was to evaluate the differences in reproductive hormone levels and their biological effects between full-term (FT) and preterm (PT) infant boys. Study Design and Participants: Twenty-five FT and 25 PT (gestational age 24.7-36.6 wk) boys were recruited at birth and followed up monthly from 1 wk to 6 months of age (d 7, months 1-6). Nineteen FT and 20 PT boys were reexamined at 14 months of age. Main Outcome Measures: Urinary gonadotropins and testosterone were measured in serial urine samples and compared with testicular and penile growth. Urinary prostate-specific antigen was measured as an androgen biomarker. Results: LH and testosterone levels were higher in PT boys (P < 0.001 for both) than FT boys. Compared with FT boys, FSH levels were lower at d 7 (P = 0.002) but higher from month 1 to month 3 (P = 0.002-0.030) in PT boys. This was associated with significantly faster testicular and penile growth in PT boys compared with FT boys. Transient increase in the prostate-specific antigen levels in both groups indicated androgen action in the prostate. Conclusions: Postnatal HPG axis activation in infancy is increased in PT boys and associated with faster testicular and penile growth compared with FT boys. Possible long-term consequences of hyperandrogenism in PT infant boys warrant further research. (J Clin Endocrinol Metab 96: 98-105, 2011)