Chronoendocrinological studies in athletes. Circadian rhythms of HGH and IRI.

The serum concentrations of HGH and IRI studied over a 24-hour span in 83 healthy athletes under normal rest conditions in a normal living environment show statistically significant rhythms, validated and quantified by cosinor analysis; for each hormone three different types of the circadian rhythm (with a peak of acrophase between: 6.30 a.m. and 1.30 p.m., 1.30 p.m. and 10.30 p.m., 10.30 p.m. and 6.30 a.m.) were observed. The IRI response to a meal load underwent cyclic variations during the day.