Thyroid Function in Experimental Streptococcal Pneumonia in the Rat

Abstract

In order to study the effects of a severe bacterial infection on thyroid function rats were subjected to group A streptococcal pneumonia, and thyroid activity determined by measurement of the rate of discharge of I131 from the thyroid gland. Decreased thyroid activity of moderate to marked degree was observed in the majority of infected animals. Infected animals ate less than normal animals. Since fasting leads to decreased thyroid function, I131 release rates were measured in control animals pair-fed with infected animals and in control and infected animals force-fed a normal intake. The reduction in thyroid activity seen in acute infection was found to be partly but not entirely due to the associated voluntary food restriction. Although the adrenal glands of rats dying of pneumonia were very large, the thyroid inhibition occurring during the course of experimental pneumonia was not secondary to increased adrenocortical function since infected, adrenalectomized animals, receiving injections of cortisone, showed thyroid inhibition comparable to that observed in intact infected animals. The possible influence of the level of thyroid activity on resistance was evaluated. In two experiments a total of 80 rats in 3 groups was pretreated with propylthiouracil and injected daily with 3 dosage levels of 7-thyroxine for 3 weeks prior to inoculation. Under these conditions mortality rates in infected animals fell with decreasing levels of thyroid function. However, induced hypothyroidism was found to afford no protective effect in comparison with untreated infected animals.

Alterations in thyroid iodine release and the peripheral metabolism of thyroxine during acute falciparum malaria in man

“…Observations in animals, of a decreased serum PBI during acute infection followed by a later rebound, are compatible with the transient depression of thyroidal 'I release rates observed in these species (2,5,6,(24)(25)(26). Modest decreases in PBI have been observed during infection in man as well, again often demonstrating a rise to normal limits or greater during recovery (4,(8)(9).…”

“…These workers invoked an increase in thyroidal secretion of To during acute infection, in view of an increased (k) in the face of no change in T, distribution space or PBI. However, an enhanced rate of To secretion is not supported by studies demonstrating suppressed thyroidal "II release during infection in various species (2,3,(24)(25)(26), or by ratios for urinary 'I/I in the present study (Fig. 6), which indicate inhibition of hormonal release.…”

“…There is ample evidence that the RAIU is depressed in a variety of animal species during acute stress due to infection, bacterial toxins, and other related noxious stimuli (2,25,(29)(30)(31). Under these circumstances, the fraction of '31I derived from the peripheral deiodination of "3I-T4 and which ordinarily would have been trapped by the thyroid, would consequently enter the urine.…”

Suppression of Thyrotropin-Releasing Hormone Gene Expression by lnterleukin-1-Beta in the Rat: Implications for Nonthyroidal Illness

“…That nonthyroidal illness is associated with a reduction in pituitary-thyroid function has been apparent for many years [1][2][3][4] but the mechanism by which this abnormality comes about is only recently becoming understood. An animal model of nonthyroidal illness that has similarities 5i VEH IL-1 to the more severe forms of human nonthyroidal illness is infectious disease, associated with low serum T4 and Ti levels and inappropriately normal or low TSH levels.…”

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

“…Leukocytes isolated from blood obtained Received for publication 9 July 1970 and in revised form 7 November 1970. ronine (TB) in several animal species, the results of such studies tend to be conflicting, appearing to vary with the nature of the species examined. In the rat, for example, acute streptococcal and pneumococcal infections appear to result in a depression of thyroid function (1,2), whereas in man data obtained after treatment of acute pneumococcal pneumonia had been instituted suggest that an increase in thyroid function might accompany this type of stress (3).…”