Changes in Thyroid Hormone Levels Within the Normal and/or Subclinical Hyper- or Hypothyroid Range Do Not Affect Circulating Irisin Levels in Humans

Abstract

Changes in thyroid-axis hormone levels within the physiological or supraphysiological range do not affect circulating irisin levels in humans. Therefore, their metabolic effects are most likely independent of each other. Other regulators of irisin levels should be identified in the future.

The association between irisin and muscle metabolism in different thyroid disorders

“…Autonomous nodules are usually associated with less severe hyperthyroidism than, for example, Graves’ disease and present primarily as a subclinical hyperthyroidism at the moment of diagnosis. Subclinical thyroid function impairment is not associated with irisin level changes . According to the obtained data, it may be assumed that FNDC5 gene expression in thyroid tissue is not associated with the development of thyroid malignancy.…”

“…Both studies confirm that short‐term disturbances in thyroid hormone concentrations do not lead to changes in irisin concentrations . Moreover, changes in thyroid hormone concentrations within the normal range or subclinical thyroid function impairments do not affect circulating irisin concentrations . Ateş et al demonstrated that circulating concentrations of irisin are elevated in hypothyroidism, and both obesity and irisin concentrations are independent risk factors for hypothyroidism .…”

“…Panagiotou et al evaluated a similar group of patients (who had undergone thyroidectomy due to thyroid cancer and had been withdrawn from their thyroxin replacement treatment for 4 weeks before radioiodine ablation) and the obtained results were consistent. Both studies confirm that short‐term disturbances in thyroid hormone concentrations do not lead to changes in irisin concentrations . Moreover, changes in thyroid hormone concentrations within the normal range or subclinical thyroid function impairments do not affect circulating irisin concentrations .…”

Serum irisin and apelin levels and markers of atherosclerosis in patients with subclinical hypothyroidism

“…Irisin was previously studied in patients with SCH (14,15), but only Stratigou and cols. evaluated serum irisin levels after being euthyroid with levothyroxine treatment (15).…”

“…found decreased irisin levels in long-standing hypothyroidism and suggested that it might result from muscle damage due to prolonged myopathy and leakage of irisin from damaged muscle cells (7). Only two studies evaluated circulating irisin levels in SCH: Although irisin levels were similar between euthyroid and subclinical hypothyroid patients in one study (14), it was reported to be increased in the other study (15). Stratigou and cols.…”