Conditions of abnormal THYROID HORMONES release in patients with apparently normal THYROID GLAND during severe systemic illness, physical TRAUMA, and psychiatric disturbances. It can be caused by the loss of endogenous hypothalamic input or by exogenous drug effects. The most common abnormality results in low T3 THYROID HORMONE with progressive decrease in THYROXINE; (T4) and TSH. Elevated T4 with normal T3 may be seen in diseases in which THYROXINE-BINDING GLOBULIN synthesis and release are increased.