Endocrine Abstracts

Sex steroid concentrations have a strong genetic determination, but environmental factors and body composition play an important role. Intrauterine growth restriction, evidenced by low birth weight has been associated with altered gonadotropin metabolism. If this relationship is also present across the wide range of birth weight is unkown. Serum sex steroid concentrations were investigated in healthy young brothers in relation to birth weight, body composition and parental steroid concentrations. A total of 677 men (25–45 years) were included in this study with 296 independent pairs of brothers and 122 fathers.

Birth weight was associated with serum testosterone (β: 0.045±0.012; P=0.0004) and sex hormone binding globulin (SHBG, β:0.0001±0.00003; P=0.0001), independent from weight, age or fat mass., whereas no association with (free) estradiol, LH or FSH was found. Paternal testosterone (P=0.02), estradiol (P=0.04) and SHBG (P=0.0004) were associated with the respective sex steroid concentrations in the brothers. Weight increase (population rank) during life, was associated with lower testosterone (−15%; P<0.001), independent from current weight and with higher free estradiol concentrations (+8%; P=0.002), whereas weight decrease was associated with higher testosterone (+13%; P<0.001).

Birth weight and parental steroid concentrations are associated with testosterone concentrations, independent from current weight, fat mass or changes in weight, extending the concept of in utero programming across the range of birth weight.