Sex differences in biomarkers of end-organ damage following exertional heat stroke in humans

Women are participating in military and athletic activities in the heat in increasing numbers, but potential sex differences in sequelae from exertional heat illness remain poorly understood. We tested the hypothesis that women suffering from exertional heat stroke (EHS) would have similar severity of organ damage biomarkers compared with men, as measured in a hospital setting. We studied women and men presenting with EHS to the emergency department at Fort Moore, GA. We measured creatinine (CR), creatine kinase (CK), alanine-transaminase (ALT), aspartate aminotransferase (AST), and estimated glomerular filtration rate (eGFR). Core temperature was also assessed by medical personnel. Biomarker data were obtained for 62 EHS cases (11 women). Men were significantly taller, and heavier, and had larger body mass index (BMI) and body surface area (<i>P</i> < 0.05 for all). The highest recorded body core temperature was not different between groups [women: 41.11°C (40.06, 41.67); men: 41.11°C (40.28, 41.72), <i>P</i> = 0.57]. Women had significantly lower peak CR [women: 1.39 (1.2, 1.48) m·dL^-1; men: 1.75 (1.53, 2.16) mg·dL^-1, <i>P</i> < 0.01] and peak CK [women: 584 (268, 2,412) U·L^-1; men: 2,183 (724, 5,856) U·L^-1, <i>P</i> = 0.02]. Peak ALT and AST were not different between groups; during recovery time points, ALT and AST were either similar or lower in women. Women spent approximately half as much time in the hospital following admittance compared with men. Our findings suggest that women may be less susceptible to organ injury resulting from EHS. Further research is necessary to understand the pathophysiology underlying these differences and how biomarkers of end-organ damage severity can differ between women and men following EHS.<b>NEW & NOTEWORTHY</b> We studied otherwise healthy women and men after exertional heat stroke in a military training environment. Peak values for biomarkers of kidney and muscle damage were lower in women compared with men despite similar (highest recorded) body core temperatures. During recovery, organ damage markers were similar or lower in women. These sex differences may indicate differences in the pathophysiology of responses, but more work is needed to clarify specific mechanisms.