Low birth weight for gestational age and subsequent male gonadal function

To verify whether a reduced birth weight for gestational age was associated with a testicular dysfunction in postpubertal boys.

Boys born small for gestational age (SGA) (n = 25) were compared to 24 born with an appropriate weight. All subjects were postpubertal (mean age 17.5 +/- 1.3 and 17.6 +/- 2.0 years, respectively). The following clinical and endocrinologic variables were evaluated: final height, target height, body mass index, testicular volume, follicle-stimulating hormone, luteinizing hormone, testosterone, and inhibin B.

The SGA group had reduced testicular size (16.3 +/- 2.7 mL vs 22.8 +/- 3.2 mL; P <.0001) with a lower testosterone level (3.76 +/- 1.35 ng/mL vs 4.77 +/- 1.55 ng/mL; P <.05) and a higher LH value (4.41 +/- 1.61 IU/L vs 3.44 +/- 1.29 IU/L; P <.05). Among the SGA group, 54% had a mean testicular volume >2 SD below the control mean (ie, <16 mL) and in these subjects, the inhibin B level was low (143 +/- 46 pg/mL vs 229 +/- 76 pg/mL; P <.0001). SGA patients with smaller testes had lower final height relative to target height(P <.05 vs patients with larger testes) and for the SGA group, inhibin B correlated with testicular size (P <.0001). Positive correlations also were found between the reduction of final height relative to target height and testicular volume (P <.005) and inhibin B values (P <.05).

SGA subjects have pituitary-gonadal axis function that tends toward hypogonadism. There is a disruption of the exocrine function in subjects with smaller testicular size who failed to show a complete height catch-up growth. This study supports a link between low birth weight and lower fertility in adult males.