The Wolff–Chaikoff effect is a presumed reduction in

thyroid hormone File:Thyroid_system.svg, upright=1.5, The thyroid system of the thyroid hormones triiodothyronine, T3 and T4 rect 376 268 820 433 Thyroid-stimulating hormone rect 411 200 849 266 Thyrotropin-releasing hormone rect 297 168 502 200 Hypothalamus r ...

levels caused by ingestion of a large amount of

iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...

. It was discovered by Drs. Jan Wolff and Israel Lyon Chaikoff at the

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...

: in 1948, they reported that injection of iodine in rats almost completely inhibited organification (thyroglobulin iodination) in the

thyroid gland The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by ...

. However, recent research into the study shows that the thyroid hormone levels of the rats were not checked prior to injections. Patients with

Graves' disease Graves' disease, also known as toxic diffuse goiter or Basedow's disease, is an autoimmune disease that affects the thyroid. It frequently results in and is the most common cause of hyperthyroidism. It also often results in an enlarged thyro ...

are more sensitive than

euthyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobe (anatomy), lobes. The lower two thirds of the lobes a ...

patients, and iodine has been used to manage Graves' disease. The Wolff–Chaikoff effect is known as an autoregulatory phenomenon that inhibits organification in the

, the formation of thyroid hormones inside the thyroid follicle, and the release of thyroid hormones into the bloodstream. This becomes evident secondary to elevated levels of circulating

iodide An iodide ion is I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine deficiency ...

. The Wolff–Chaikoff effect is an effective means of rejecting a large quantity of imbibed iodide, and therefore preventing the thyroid from synthesizing large quantities of thyroid hormone. Excess iodide transiently inhibits thyroid iodide organification. In individuals with a normal thyroid, the gland eventually escapes from this inhibitory effect and iodide organification resumes; however, in patients with underlying autoimmune thyroid disease, the suppressive action of high iodide may persist. The Wolff–Chaikoff effect lasts several days (around 10 days), after which it is followed by an "escape phenomenon," which is described by resumption of normal organification of iodine and normal thyroid peroxidase function. "Escape phenomenon" is believed to occur because of decreased inorganic iodine concentration inside the thyroid follicle below a critical threshold secondary to down-regulation of

sodium-iodide symporter The sodium/iodide cotransporter, also known as the sodium/iodide symporter (NIS), is a protein that in humans is encoded by the ''SLC5A5'' gene. It is a transmembrane glycoprotein with a molecular weight of 87 kAtomic mass unit, Da and 13 transmem ...

(NIS) on the basolateral membrane of the thyroid follicular cell. The Wolff–Chaikoff effect has been used as a treatment principle against

hyperthyroidism Hyperthyroidism is a endocrine disease in which the thyroid gland produces excessive amounts of thyroid hormones. Thyrotoxicosis is a condition that occurs due to elevated levels of thyroid hormones of any cause and therefore includes hyperth ...

(especially

thyroid storm Thyroid storm is a rare but severe and life-threatening complication of hyperthyroidism. It occurs when an overactive thyroid leads to hypermetabolism, which can cause death from cardiac arrest or multiple organ failure. It is characterized by ...

) by infusion of a large amount of iodine to suppress the thyroid gland. Iodide was used to treat hyperthyroidism before antithyroid drugs such as

propylthiouracil Propylthiouracil (PTU) is a medication used to treat hyperthyroidism. This includes hyperthyroidism due to Graves' disease and toxic multinodular goiter. In a thyrotoxic crisis it is generally more effective than methimazole. Otherwise it is ...

and

methimazole Thiamazole, also known as methimazole, is a medication used to treat hyperthyroidism. This includes Graves' disease, toxic multinodular goiter, and thyrotoxic crisis. It is taken by mouth. Full effects may take a few weeks to occur. Commo ...

were developed. Hyperthyroid subjects given iodide may experience a decrease in

basal metabolic rate Basal metabolic rate (BMR) is the rate of energy expenditure per unit time by endothermic animals at rest.. In other words it is the energy required by body organs to perform normal It is reported in energy units per unit time ranging from watt ( ...

that is comparable to that seen after

thyroidectomy A thyroidectomy is an operation that involves the surgery, surgical removal of all or part of the thyroid gland. In general surgery, endocrine or head and neck surgeons often perform a thyroidectomy when a patient has thyroid cancer or some other ...

. The Wolff–Chaikoff effect also explains the

hypothyroidism Hypothyroidism is an endocrine disease in which the thyroid gland does not produce enough thyroid hormones. It can cause a number of symptoms, such as cold intolerance, poor ability to tolerate cold, fatigue, extreme fatigue, muscle aches, co ...

produced in some patients by several iodine-containing drugs, including

amiodarone Amiodarone is an antiarrhythmic medication used to treat and prevent a number of types of cardiac dysrhythmias. This includes ventricular tachycardia, ventricular fibrillation, and wide complex tachycardia, atrial fibrillation, and paroxys ...

. The Wolff–Chaikoff effect is part of the mechanism for the use of potassium iodide in nuclear emergencies. The Wolff–Chaikoff effect is subject to an escape phenomenon that limits its action after several days. It is to be distinguished from the

Plummer effect The Plummer effect is one of several physiological Feed forward (control), feedforward mechanisms taking place in Thyroid follicular cell, follicular cells of the healthy thyroid gland and preventing the development of thyrotoxicosis in situations ...

, which inhibits the proteolysis of

thyroglobulin Thyroglobulin (Tg) is a 660 kDa, dimeric glycoprotein produced by the follicular cells of the thyroid and used entirely within the thyroid gland. Tg is secreted and accumulated at hundreds of grams per litre in the extracellular compartment ...

and the release of pre-formed thyroid hormones from follicles. Both effects operate on different time scales. Only the Wolff–Chaikoff effect is helpful to prevent the thyroid from uptaking radioactive iodine in the case of nuclear emergencies. Therefore, "plummering" with high-dose iodine is only effective in a short time window after the release of radionuclides. Wrong timing of iodine use may even increase the risk by triggering the Plummer effect. The Plummer effect, the Wolff-Chaikoff inhibition effect, and the adaptive escape phenomenon, synergistically work together to fend off potentially harmful consequences of excess iodine load and ensure thyroid homeostasis.

References

{{DEFAULTSORT:Wolff-Chaikoff effect Iodine Thyroid

See also

References