Context: Prenatal growth restriction may affect future fertility in both females and males. Studies have shown that growth retarded male rats have different sexual behavior and disturbed steroidogenesis.

Objective: We hypothesized that adult human males born SGA have an altered sex hormone profile.

Design, setting and patients: 25 adult males born SGA with median birth weight –2.2 SDS and birth length –2.4 SDS were studied. Median age was 23.1 years and final height -0.5 SDS. They were compared with 44 male controls with median age 20.5 years and final height 0.4 SDS.

Main outcome measure: The primary outcome before the study started was 17-estradiol (E₂) levels in SGA males.

Results: The SGA group showed significantly higher median levels of E₂ 17.9 pg/ml (p<0.001) and dihydrotestosterone (DHT) 0.543 ng/ml (p< 0.05), compared to controls 12.6 pg/ml and 0.423 ng/ml, respectively. Testosterone (T) levels did not differ between groups. E₂/T ratio correlated negatively to birth weight (r=-0.40, p<0.01) and birth length (r=-0.44, p<0.001). DHT/T ratio correlated negatively to birth weight (r=-0.51, p<0.001) and birth length (r=-0.38, p<0.01). Males born SGA also had significantly higher median levels of inhibin B 164 pg/ml (p<0.05) compared to controls 137 pg/ml. Inhibin B correlated negatively to birth length (r=-0.34, p<0.01).

Conclusion: SGA males of normal stature have higher levels of 17-estradiol, dihydrotestosterone and inhibin B than controls, indicating a disturbed steroid synthesis or metabolism. Aromatase activity, calculated as E₂/T ratio, and 5-reductase activity, calculated as DHT/T ratio is negatively correlated to size at birth.