Department of Internal Medicine and Chronobiology Unit, Scientific Institute and Regional General Hospital, Casa Sollievo della Sofferenza, S.Giovanni Rotondo (FG), Italy.
J Biol Regul Homeost Agents. 2011 Apr-Jun;25(2):249-57.
Neuro-endocrine hormone secretion is characterized by circadian rhythmicity. Melatonin, GRH and GH are secreted during the night, CRH and ACTH secretion peak in the morning, determining the circadian rhythm of cortisol secretion, TRH and TSH show circadian variations with higher levels at night. Thyroxine levels do not change with clear circadian rhythmicity. In this paper we have considered a possible influence of cortisol and melatonin on hypothalamic-pituitary-thyroid axis function in humans. Melatonin, cortisol, TRH, TSH and FT4 serum levels were determined in blood samples obtained every four hours for 24 hours from ten healthy males, aged 36-51 years. We correlated hormone serum levels at each sampling time and evaluated the presence of circadian rhythmicity of hormone secretion. In the activity phase (06:00 h-10:00 h-14:00 h) cortisol correlated negatively with FT4, TSH correlated positively with TRH, TRH correlated positively with FT4 and melatonin correlated positively with TSH. In the resting phase (18:00 h-22:00 h-02:00 h) TRH correlated positively with FT4, melatonin correlated negatively with FT4, TSH correlated negatively with FT4, cortisol correlated positively with FT4 and TSH correlated positively with TRH. A clear circadian rhythm was validated for the time-qualified changes of melatonin and TSH secretion (with acrophase during the night), for cortisol serum levels (with acrophase in the morning), but not for TRH and FT4 serum level changes. In conclusion, the hypothalamic-pituitary-thyroid axis function may be modulated by cortisol and melatonin serum levels and by their circadian rhythmicity of variation.
神经内分泌激素的分泌具有昼夜节律性。褪黑素、GRH 和 GH 在夜间分泌，CRH 和 ACTH 的分泌在早上达到峰值，决定了皮质醇分泌的昼夜节律，TRH 和 TSH 的水平呈昼夜变化，夜间水平较高。甲状腺素水平没有明显的昼夜节律变化。本文考虑了皮质醇和褪黑素对人类下丘脑-垂体-甲状腺轴功能的可能影响。在 10 名年龄在 36-51 岁的健康男性中，每 4 小时采集一次血液样本，共 24 小时，测定血清中褪黑素、皮质醇、TRH、TSH 和 FT4 水平。我们在每个采样时间对激素血清水平进行了相关性分析，并评估了激素分泌的昼夜节律性。在活动期（06:00 h-10:00 h-14:00 h），皮质醇与 FT4 呈负相关，TSH 与 TRH 呈正相关，TRH 与 FT4 呈正相关，褪黑素与 TSH 呈正相关。在休息期（18:00 h-22:00 h-02:00 h），TRH 与 FT4 呈正相关，褪黑素与 FT4 呈负相关，TSH 与 FT4 呈负相关，皮质醇与 FT4 呈正相关，TSH 与 TRH 呈正相关。验证了褪黑素和 TSH 分泌的时间定量变化（夜间出现高峰）、皮质醇血清水平（早晨出现高峰）具有明显的昼夜节律性，但 TRH 和 FT4 血清水平变化则没有。结论：下丘脑-垂体-甲状腺轴功能可能受皮质醇和褪黑素血清水平及其昼夜节律变化的调节。
