Samuels M H
Division of Endocrinology, Diabetes, and Clinical Nutrition, Oregon Health Sciences University, Portland 97201, USA.
J Clin Endocrinol Metab. 2000 Apr;85(4):1388-93. doi: 10.1210/jcem.85.4.6540.
Although pharmacological doses of glucocorticoids suppress TSH secretion, less is known regarding the effects of physiological variations in cortisol levels on TSH. To study this issue, seven subjects with primary adrenal insufficiency each underwent four studies. In the first study subjects received infusions of saline for 48 h (baseline study). In the second study subjects received infusions of hydrocortisone for 48 h in a pulsatile and diurnal pattern that replicated serum cortisol levels in healthy subjects (physiological study). In most cases, the dose of hydrocortisone was 19 mg/24 h, but this was adjusted as necessary until the resulting serum cortisol levels reproduced those seen in healthy, nonstressed control subjects. In the third study subjects received the same total dose of hydrocortisone as in the physiological study, but with pulses of equal magnitude spaced evenly throughout the time period (constant study). In the fourth study subjects received the same total dose of hydrocortisone, but with the diurnal pattern shifted 12 h from the physiological infusion (reversed study). TSH levels were measured every 15 min during the final 24 h of each study. During the baseline study, the 24-h mean TSH level was 2.87 +/- 0.56 mU/L and did not exhibit any diurnal variation. During the physiological study, daytime TSH levels decreased 39% compared to those during the baseline study due to decreased TSH pulse amplitude, and the normal TSH diurnal rhythm was reestablished. The constant and reversed studies did not lead to significant changes in serum TSH levels compared to baseline. These results suggest that the normal circadian variation in endogenous cortisol levels may control TSH secretion, with maximal TSH suppression seen during the time when cortisol levels are highest. However, changing the diurnal pattern of hydrocortisone infusion did not lead to reciprocal changes in TSH levels, and the specific nature of the interactions between cortisol and TSH within the physiological range remains to be fully elucidated.
虽然药理剂量的糖皮质激素会抑制促甲状腺激素（TSH）的分泌，但关于皮质醇水平的生理变化对TSH的影响，人们了解得较少。为研究此问题，7名原发性肾上腺功能不全的受试者每人都接受了四项研究。在第一项研究中，受试者接受48小时的生理盐水输注（基线研究）。在第二项研究中，受试者以模拟健康受试者血清皮质醇水平的脉冲式和昼夜模式接受48小时的氢化可的松输注（生理研究）。在大多数情况下，氢化可的松的剂量为19毫克/24小时，但会根据需要进行调整，直到所产生的血清皮质醇水平重现健康、未受应激的对照受试者的水平。在第三项研究中，受试者接受与生理研究中相同总剂量的氢化可的松，但在整个时间段内等幅度脉冲均匀分布（恒定研究）。在第四项研究中，受试者接受相同总剂量的氢化可的松，但昼夜模式相对于生理输注提前12小时（颠倒研究）。在每项研究的最后24小时内，每15分钟测量一次TSH水平。在基线研究期间，24小时平均TSH水平为2.87±0.56毫国际单位/升，且未表现出任何昼夜变化。在生理研究期间，由于TSH脉冲幅度降低，白天TSH水平与基线研究期间相比下降了39%，并且重新建立了正常的TSH昼夜节律。与基线相比，恒定研究和颠倒研究未导致血清TSH水平发生显著变化。这些结果表明，内源性皮质醇水平的正常昼夜变化可能控制TSH的分泌，在皮质醇水平最高时TSH受到最大抑制。然而，改变氢化可的松输注的昼夜模式并未导致TSH水平发生相应变化，皮质醇与TSH在生理范围内相互作用的具体性质仍有待充分阐明。
