Most of mammalian physiology is under the control of biological rhythms, including the endocrine system with time-varying hormone secretion. Precision neuroimaging studies provide unique insights into how the endocrine system dynamically regulates aspects of the human brain. Recently, we established estrogen's ability to drive widespread patterns of connectivity and enhance the global efficiency of large-scale brain networks in a woman sampled every 24 h across 30 consecutive days, capturing a complete menstrual cycle. Steroid hormone production also follows a pronounced sinusoidal pattern, with a peak in testosterone between 6 and 7 A.M. and nadir between 7 and 8 P.M. To capture the brain's response to diurnal changes in hormone production, we carried out a companion precision imaging study of a healthy adult man who completed MRI and venipuncture every 12–24 h across 30 consecutive days. Results confirmed robust diurnal fluctuations in testosterone, 17β-estradiol—the primary form of estrogen—and cortisol. Standardized regression analyses revealed widespread associations between testosterone, estradiol, and cortisol concentrations and whole-brain patterns of coherence. In particular, functional connectivity in the Dorsal Attention Network was coupled with diurnally fluctuating hormones. Further, comparing dense-sampling datasets between a man and a naturally cycling woman revealed that fluctuations in sex hormones are tied to patterns of whole-brain coherence in both sexes and to a heightened degree in the male. Together, these findings enhance our understanding of steroid hormones as rapid neuromodulators and provide evidence that diurnal changes in steroid hormones are associated with patterns of whole-brain functional connectivity.

哺乳动物的大部分生理机能都受到生物节律的控制，包括随时间变化的激素分泌的内分泌系统。精密神经影像研究为内分泌系统如何动态调节人脑的各个方面提供了独特的见解。最近，我们在连续 30 天内每 24 小时采样一次的女性中，确定了雌激素能够驱动广泛的连接模式并提高大规模大脑网络的整体效率，从而捕获完整的月经周期。类固醇激素的产生也遵循明显的正弦曲线模式，睾丸激素在上午 6 点至 7 点之间达到峰值，而在下午 7 点至 8 点之间达到最低点。连续 30 天每 12-24 小时完成一次 MRI 和静脉穿刺的成年男性。结果证实了睾酮、17β-雌二醇（雌激素的主要形式）和皮质醇的剧烈昼夜波动。标准化回归分析揭示了睾酮、雌二醇和皮质醇浓度与全脑一致性模式之间的广泛关联。特别是，背部注意力网络中的功能连接与昼夜波动的激素相结合。此外，比较男性和自然循环女性之间的密集采样数据集发现，性激素的波动与两性的全脑一致性模式有关，并且与男性的高度一致性有关。总之，这些发现增强了我们对类固醇激素作为快速神经调节剂的理解，并提供了类固醇激素的昼夜变化与全脑功能连接模式相关的证据。