Investigation of the secretion and metabolism of cortisol during a 100 km race using [4-14C] and [1 1α-3H] cortisol

Abstract

Abstract. A mixture of [11α-3H] and [4-14C]cortisol was administered orally to healthy men, following which urine was collected for 24 h. Four subjects acted as basal controls, going about their normal (sedentary) work; a further 3 resting subjects also received 100 mg cortisol orally (high cortisol controls) and 6 subjects competed in a 100 km race. Decreases in the carbon-14 specific activity of the cortisol metabolite excreted by the runners suggested that they seceted cortisol at 2–4 times the rate of the basal controls. This change was mirrored by the excretion of urine free cortisol but not by that of 17-hydroxycorticosteroids. The isotope ratio (3H:14C) of 11-hydroxy metabolites of cortisol from the runners was intermediate between those of the basal and high cortisol controls, from which we conclude that though the fractional oxidation of cortisol to cortisone is reduced by increasing the cortisol pool, it is not affected by exercise per se. This and other results show that although continuous running for 6–8 h, involving energy expenditure in excess of 25 megajoules, leads to a moderate increase in the rate of cortisol secretion, running per se does not appear to markedly affect the metabolism of cortisol.