Altered circadian plasma cortisol and aldosterone group rhythms in Cushing's syndrome versus obesity and health.
According to textbooks, Cushing's syndrome (CS) is associated with a loss of the circadian rhythmicity in circulating cortisol. Documented cases of a persisting rhythm in CS are regarded as an exception. Herein, we show that a circadian rhythmicity in plasma cortisol, albeit of much reduced amplitude and with altered timing, remains a group characteristic of patients with CS, characterized further by a circadian rhythm in circulating aldosterone. In Lubochna, Czechoslovakia, 28 patients with CS, 120 patients with obesity imitating CS, 70 subjects with simple obesity, and 19 nonobese controls were sampled at 0800, 1600, 2000, 0000, and again at 0800 on the following day. In Rome, five women and three men with CS and 27 women and 30 men in clinical health gave blood for aldosterone determinations at 0600, 0800, 1200, 1800, 2000, and 0000. Results were first analyzed by single cosinor and then summarized by population-mean cosinor. A group rhythm was demonstrated for all categories of subjects by the methods employed, although, compared to health and even to simple obesity or Cushing-imitating obesity, the amplitude of the rhythm in CS was much reduced. Subgrouping according to etiology and individualized assessment in practice are mandatory. The scope of this group rhythm assessment, however, is merely to document that as a general rule the circadian rhythms in circulating cortisol and aldosterone persist in CS documented by surgery or at autopsy.