Rat corticotropin, insulin and thyroid hormone levels during the acute phase response to inflammation

Circulating levels of corticotropin, thyroid hormones and insulin were measured in rats at various times after turpentine-induced inflammation. Corticotropin increased rapidly showing a biphasic response with a four-fold increase at about 6-8 hr after inflammation and a 10-fold increase at 10 hr after inflammation. The response of insulin to inflammation was slower than corticotropin and the magnitude of the increase was smaller. Insulin increased by three-fold at 20 hr after inflammation. Thyroid hormone levels were depressed by turpentine inflammation. Levels fell after 4 hr and remained at low levels throughout. Administration of a cytokine preparation to rats also caused depressed thyroxine levels at short intervals after administration. However, levels increased at longer intervals after administration. This suggests that, like corticotropin and insulin, thyroid hormone levels could be under the control of immunotransmitters during the acute phase response.