Thyroid Therapy or Dysfunction in Athletes: Is it Time to Revisit the Clinical Practice Guidelines?

Recent media have highlighted the controversy surrounding treatment of elite athletes for hypothyroidism. The World Anti-Doping Agency denied a request by the United States Anti-Doping Agency to ban the use of thyroid medication. At present, there is no scientific evidence that thyroid medication has the potential to enhance performance. Clinical practice guidelines are not definitive in regard to what classifies a patient as having hypothyroidism. Thyroid-stimulating hormone and free T4 are recommended to screen for thyroid disease; however, the thyrotropin-releasing hormone stimulation test is still advocated by some for detecting the earliest stages of hypothyroidism. Hypothyroidism has been demonstrated to reduce cardiopulmonary function and result in musculoskeletal symptoms, such as fatigue and muscle stiffness. Symptoms of hypothyroidism, including depression, fatigue, and impaired sleep, are similar to those reported in overtraining. These patients may have hypothalamic-pituitary dysfunction that may complicate interpretation of basal thyroid-stimulating hormone and free T4. To date, no association has been identified between training state and hypothyroidism. Research to more clearly define hypothyroidism using provocative testing, evaluate the potential for thyroid medication to enhance performance, and examine whether training may induce hypothyroidism in athletes is desirable.