T-Lymphocyte Cytokine Production Patterns in Nonimmune Severe Hypothyroid State and After Thyroid Hormone Replacement Therapy

The influence of thyroid hormones on the immune system is controversial. We analyzed the cytokine expression pattern of T lymphocytes in patients with severe nonimmune hypothyroidism in order to establish the role of thyroid hormones on the immune system. The study comprised 7 patients(1 male and 6 females) 20 to 76 years of age (mean age, 53 years), without signs of chronic thyroiditis, verified by histology and laboratory data. The patients were studied 5 weeks after total thyroidectomy. Peripheral blood mononuclear cell (PBMC) cultures and intracellular cytokine detection by flow cytometry before and after thyroid hormone replacement therapy were performed (free thyroxine [FT₄] 0.030 ± 0.034 ng/dL, versus FT₄: 2.16 ± 0.68 ng/dL). The control group consisted of 7 healthy subjects (FT₄: 1.20 ± 0.21 ng/dL). We found no significant differences in the cytokine pattern (interferon [IFN]-γ, IL-2, interleukin [IL]-4, IL-5, IL-6, IL-10, IL-13, tumor necrosis factor [TNF]-α, TNF-β) of CD4⁺ and CD8⁺ between the matched groups (hypothyroid subjects versus controls, levothyroxine treated subjects versus controls). Our data show no change in the type 1/type 2 balance of peripheral CD4⁺ and CD8⁺ T lymphocytes from patients with nonimmune hypothyroidism. According to our results, the hypothyreotic state does not contribute to the reported changes in cytokine production patterns in Hashimoto's thyroiditis.