TEMPORAL VARIATIONS OF TESTOSTERONE LEVELS IN THE PERIPHERAL BLOOD PLASMA OF MEN

Abstract

SUMMARY Testosterone was measured in the peripheral blood plasma of normal men by radioimmunoassay. The results were analysed to test for the possible existence of a circadian rhythm, for fluctuations superimposed on any such rhythm, and for day-to-day variations. Unequivocal evidence of a circadian rhythm was found in all but one of the subjects studied and the cycle appeared to be accompanied by a series of fluctuations of lower amplitude lasting for 1–2 h. Samples taken from the same subjects on consecutive days showed marked variation between days, but no regular cyclic pattern. The possible existence of such a cycle is not, however, eliminated. On the basis of all the data obtained a regime is suggested for the collection of blood samples from individuals whose androgenic status is to be assessed.