Neuro-endocrine correlations of hypothalamic-pituitary-thyroid axis in healthy humans

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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 (06:00h-10:00h-14:00h) 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 (18:00h-22:00h-02:00h) 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.

Original languageEnglish
Pages (from-to)249-257
Number of pages9
JournalJournal of Biological Regulators and Homeostatic Agents
Issue number2
Publication statusPublished - Apr 2011


  • Circadian rhythmicity
  • HHT
  • Neuro-endocrine system

ASJC Scopus subject areas

  • Oncology
  • Endocrinology, Diabetes and Metabolism
  • Physiology (medical)
  • Immunology and Allergy
  • Immunology
  • Endocrinology
  • Physiology
  • Cancer Research


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