Plasma levels of adrenocorticotropic hormone (ACTH) and cortisol were measured in young adults with influenza virus type A (H 3 N 2 ) infection for whom cultures were positive and in comparable controls without symptoms or other evidence of illness. The mean plasma ACTH level { SE in 19 patients with acute influenza was 13.5 { 2.1 pg/mL compared with 23 { 3.2 pg/mL in 11 controls (P Å .02). Mean plasma ACTH levels { SE had risen to 21 { 4.1 pg/mL in specimens obtained from patients during

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... escence. The mean plasma cortisol level { SE in patients with acute influenza was 13.7 { 1.4 mg/dL compared with 10.8 { 1.0 mg/dL in controls (P Å not significant). ACTH levels in individual controls were relatively higher than their cortisol levels, but ACTH levels in patients tended to be lower than cortisol levels in paired specimens. These findings suggest that influenza virus type A infection may have an inhibitory effect on the production or release of ACTH. pg/mL (72 pmol/L), respectively. Serum cortisol concentrations