Thyroid Disorders in Sport

Thyroid disorders matter in sport because their symptoms overlap closely with overtraining and relative energy deficiency in sport (RED-S), so they are easy to miss or to over-diagnose.

• •Hyperthyroidism means the thyroid gland itself is overproducing hormone.
• •Thyrotoxicosis is the wider state of excess thyroid hormone from any source, including thyroiditis or exogenous hormone.

The 2 problems seen in practice are hypothyroidism and thyrotoxicosis, both investigated with a blood test led by thyroid-stimulating hormone (TSH) and free thyroxine (free T4). The skills are reading these tests correctly, telling thyroid disease from the reversible axis changes of low energy availability, and managing treatment, return to sport and anti-doping.