Male testosterone (T) decreases in response to childbirth. Longitudinal support for this has come from samples across cultures. In this study, we look at individual differences in this phenomenon. Utilizing a sample of U.S. fathers, we employ life history theory to investigate the influence of a father's early experience on his neuroendocrine response to fatherhood. We conducted three home visits (n = 226 fathers) from the third trimester of pregnancy to when infants were 10 months old. In this sample, T declined from the third trimester of (a partner's) pregnancy to the early months of the postnatal period. T recovered to pre-birth levels by the time infants reached 10 months old. We did not find any evidence that one's subjective experience of their early environment could account for any meaningful variability in T calibration. Objective, "event" measures of early harshness (i.e., death of a sibling/friend) and unpredictability (i.e., parent upheaval) each uniquely predicted a younger age of sexual debut. Neither harshness nor unpredictability had any (direct or indirect) effects on T calibration. Age of sexual debut did predict the rate of T recovery from 3 to 10 months postnatal. The younger one's sexual debut, the more accelerated their T ascent during this period. We discuss the potential reasons for, and implications of our mixed results.

中文翻译：

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男性睾丸激素的生活史和个体差异：睾丸激素对初生父亲的反应的早期环境校准的混合证据。

男性睾丸激素（T）随着分娩而减少。跨文化的样本对此提供了纵向支持。在这项研究中，我们着眼于这种现象的个体差异。利用美国父亲的样本，我们运用生活史理论研究父亲的早期经历对父亲对父亲的神经内分泌反应的影响。从孕晚期到婴儿10个月大时，我们进行了3次家访（n = 226位父亲）。在该样本中，T从（同伴）妊娠的三个月下降到产后早期。当婴儿达到10个月大时，T恢复到出生前的水平。我们没有发现任何证据表明其早期环境的主观经验可以解释T校准中任何有意义的变化。客观的，“事件性”的早期苛刻度（即，兄弟姐妹/朋友的死亡）和不可预测性（即，父母的动荡）的度量均独特地预测了性行为首次出现的年龄。苛刻性和不可预测性都不会对T校准产生任何（直接或间接）影响。首次性生活的年龄确实可以预测出生后3到10个月的T恢复率。年轻人的性行为越年轻，在此期间他们的T上升速度就越快。我们讨论了混合结果的潜在原因及其影响。首次性生活的年龄确实可以预测出生后3到10个月的T恢复率。年轻人的性行为越年轻，在此期间他们的T上升速度就越快。我们讨论了混合结果的潜在原因及其影响。首次性生活的年龄确实可以预测出生后3到10个月的T恢复率。年轻人的性行为越年轻，在此期间他们的T上升速度就越快。我们讨论了混合结果的潜在原因及其影响。