Alterations in thyroid hormone economy during acute infection with Diplococcus pneumoniae in the rhesus monkey

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Abstract
In order to study the alterations in thyroid hormone economy that accompany an acute bacterial infection, rhesus monkeys were inoculated i.v. with a virulent Diplococcus pneumoniae culture containing approximately 108 organisms per dose. This was found to produce a well-defined febrile illness followed in most instances by spontaneous recovery, thereby permitting sequential observations to be made during progression from the healthy state through acute infection into convalescence. During the acute febrile period of the infection, the clearance of both exogenously labeled L-thyroxine (T4) and 3,3′,5-triiodo-L-thyronine (T3) from their peripheral pools was accelerated. This alteration was often evident by 8 hr after inoculation with the virulent culture and could not be ascribed to a decrease in extracellular binding. Despite the accelerated hormonal clearance, the concentrations of both endogenously labeled thyroid hormone and stable T4 in the sera of the surviving monkeys remained essentially unchanged or increased, indicating that hormonal secretion must have increased during this period. During the convalescent period, hormonal clearance was similar to preinfection control values. Leukocytes isolated from blood obtained 6 hr after inoculation with the virulent culture displayed enhanced T4-deiodinative activity.