title: Acute administration of melatonin at two opposite circadian stages does not change responses to gonadotropin releasing hormone, thyrotropin releasing hormone and ACTH in healthy adult males.
abstract: We evaluated the effect of a single oral administration of 100 mg melatonin (MT) vs placebo (PL) on the pituitary release of LH, FSH, TSH and prolactin (PRL) after GnRH + TRH and on the adrenocortical release of cortisol, aldosterone and progesterone after ACTH in healthy adult males. We carried out a double blind study in 6 volunteers in winter, at two opposite stages of the circadian cycle: 08:00 and 20:00 h. Injection of GnRH (100 micrograms), TRH (200 micrograms) and ACTH (10 micrograms of the synthetic ACTH 1-17 analogue, Alsactide) was performed one h after MT or PL ingestion. Plasma MT levels were 200-4,000-fold higher after MT than PL thus confirming the effective gastrointestinal absorption of the pineal hormone. The hormonal patterns were superimposable after MT and PL. A higher response of PRL, FSH and cortisol was observed in the evening vs morning protocols independently of previous MT or PL. Our data demonstrate that the acute oral administration of a pharmacological dose of MT at two opposite circadian stages is ineffective to change a variety of pituitary and adrenocortical responses in human male subjects. The circadian chronosusceptibility of pituitary and adrenocortical cells to specific stimuli deserves interest to future investigation.
authors.affiliation: Dipartimento di Biomedicina, Ospedale S. Vito, Torino, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Paccotti
authors.forename: M
authors.initials: M
authors.lastname: Terzolo
authors.forename: M
authors.initials: M
authors.lastname: Torta
authors.forename: A
authors.initials: A
authors.lastname: Vignani
authors.forename: M
authors.initials: M
authors.lastname: Schena
authors.forename: A
authors.initials: A
authors.lastname: Piovesan
authors.forename: A
authors.initials: A
authors.lastname: Angeli
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000328:Adult; D002940:Circadian Rhythm; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D008550:Melatonin / Q000009:adverse effects / Q000097:blood / Q000494:pharmacology*; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology; D010908:Pituitary Hormones, Anterior / Q000097:blood*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
chemical_list: D010906:Pituitary Hormone-Releasing Hormones; D010908:Pituitary Hormones, Anterior; D013973:Thyrotropin-Releasing Hormone; D000324:Adrenocorticotropic Hormone; D008550:Melatonin; D006854:Hydrocortisone