Excess free cortisol is filtered in kidneys and dumped into the urine.

过量的游离皮质醇经肾脏过滤排入尿中。

In fact, only this small fraction of free cortisol is biologically active, and its levels are carefully controlled.

实际上，只有一小部分的游离皮质醇具备生物活性，其水平被严格控制。

Free cortisol in the blood is involved in a bunch of stuffs and it's part of the circadian rhythm.

血液中的游离皮质醇有很多作用，也涉及昼夜节律。

For all this to work properly, though, the levels of free cortisol have to stay within the normal range.

不过，想要这些都正常运作，皮质醇水平就必须保持在正常水平。

Diagnosis of Cushing syndrome is initially based on measuring the free, or unbound cortisol in a 24-hour urine sample, in order to assess the total amount of cortisol excreted in the urine over a 24-hour period.

库欣综合征最开始的诊断时基于测量24小时尿液样品里的游离皮质醇，以计算过去24小时内排出体外的尿液中皮质醇的总量。