Evolutionary endocrinology: information encoded in steroid hormone concentrations

作为进化内分泌学家，我们是精确测量唾液、血液和蛋黄等生物体液中激素的专家。这些技能支持的学生项目多种多样，包括青春期抑郁症的激素参与、老年男性的睾酮变异、成为父亲的男性的激素变化、对压力的慢性和急性反应、母亲压力对胚胎发育的跨代影响，以及个体内部的激素动态。了解个体体内的激素动态是该提案的重点，实验从一个个体中获得多达24个小样本，然后计算个体每天经历的激素变异性。尽管我们的新方法提供了严格的实验控制和小的测量误差，但我们发现重复采样揭示了巨大的可变性。例如，在一只雄性仓鼠体内，在24个重复样本中，睾酮浓度在低20到高2000纳克/分升之间。无论是测量性激素还是压力激素，男性、女性和青春期女孩的差异也很大。此外，我们有初步证据表明，我们衡量可变性的指标，即动态指数，会在人生的关键阶段发生变化，比如成为父亲，也会对生活方式的选择做出反应，比如运动和饮食。以浓度编码信息，以及围绕该浓度的动态变化，将使一种激素携带两个独立的信息。因此，拟议的研究将检验我们的假设，即激素变异性，或“噪音”，包含激素“信号”。如果这一假设得到支持，我们的结果将改变未来的实验设计，弥合激素和行为之间缺失的联系，并最终可能导致激素传递的改变，从而降低健康风险。

As evolutionary endocrinologists, we are experts in the precise measurement of hormones in biological fluids such as saliva and blood and egg yolk. These skills support student projects as diverse as hormone involvement in adolescent onset depression, testosterone variability in aging men, hormonal changes in men becoming fathers, chronic and acute responses to stress, trans-generational effects of maternal stress on development of embryos, and hormone dynamics within individuals. Understanding hormone dynamics within individuals is the focus of this proposal, with experiments that obtain up to 24 small samples from one individual and then calculate the hormonal variability that the individual experiences from day to day. In spite of our new methods that provide tight experimental controls and small measurement error, we find that repeated sampling reveals huge variability. Within one male hamster, for example, testosterone concentrations fall anywhere between a low of 20 and a high of 2000 ng/dL over 24 repeated samples. Variability is also large in men, women, and adolescent girls, whether measured for sex hormones or for stress hormones. In addition, we have preliminary evidence that our measure of variability, the dynamic index, can change at critical transitions in life, such as becoming a father, and in response to lifestyle choices, such as exercise and diet. Coding information in concentration, and in dynamic variability around that concentration, would enable one hormone to carry two independent messages. Thus, proposed research will test our hypothesis that hormone variability, or 'noise', contains a hormone 'signal'. If the hypothesis is supported, our results will transform future experimental designs, bridge missing links between hormones and behaviour, and, eventually, might lead to changes in hormone delivery that reduce health risks.