Autoregulation of thyroid function by iodide

The First department of Internal Medicine Nagasaki University School of Medicine Nagasaki, 852, Japan 

The concept of autoregulation of iodide metabolism was established several decades ago and autoregulation was originally defined as the regulation of thyroidal iodine metabolism independent from TSH or other externeil stimulators, and the major autoregulatory factor was considered to be excess iodide. 

However, it is important to note that the concept was established when the methods of investigation were determinations of bioactive TSH and protein-bound iodide, and dynamics of radioactive iodine. 

Acute Inhibitory Effects of Iodide and Escape from the Acute Inhibitory Effect 

Acute inhibitory effects of excess iodide was first demonstrated in vitro in 1944 by Morton, Chaikoff and Rosenfeld (i) and in vivo in 1948 by Wolff and Chaikoff (Wolff-Chaikoff effect) (2). As shown in Fig. 1, they injected 100 pg of iodide per rat with a tracer dose of and determined pleisma inorganic iodide concentration, total thyroidal iodine uptake and thyroidal organic iodine uptake until 50 hours after the injection of iodide. Thyroidal organic iodine 

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