Effects of exogenous melatonin on human pituitary and adrenal secretions. Hormonal responses to specific stimuli after acute administration of different doses at two opposite circadian stages in men.

We evaluated the effect of an acute oral administration of 2 dosages (100 and 1 mg) of melatonin (MT) vs placebo (PL) on pituitary release of LH, FSH, TSH and 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 on 6 volunteers in winter-early spring, at 2 opposite phases of the circadian cycle: 08(00) and 20(00). Injection of GnRH (100 micrograms), TRH (200 micrograms) and ACTH (10 micrograms of the synthetic analogue ACTH 1-17, alsactide) was performed 1 h after MT or PL ingestion.

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.

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.

Circadian rhythm of the angiotensin converting enzyme (ACE) activity in serum of healthy adult subjects.

Angiotensin converting enzyme (ACE) activity was measured in the peripheral serum of 10 healthy, diurnally-active and nocturnally-resting adult subjects (5 women and 5 men). Blood was drawn serially at 4-h intervals throughout a 24-h cycle with the subjects hospitalized and synchronized. They were not kept in recumbency.