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Table salt iodization affects incidence of iodine-induced hyperthyroidism, hypothyroidism
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The incidence of iodine-induced hyperthyroidism fell and the incidence of iodine-induced hypothyroidism rose after a mandatory increase in potassium iodide concentration in table salt in Slovenia, according to recent findings.
Simona Gaberšček, MD, PhD, assistant professor in the department of nuclear medicine, University Medical Centre Ljubljana in Slovenia, and colleagues evaluated medical records of 885 patients with iodine-induced hyperthyroidism or iodine-induce hypothyroidism between 1998 and 2009 at the University Medical Centre Ljubljana.
In 1999, the mandatory iodization of kitchen salt increased from 10 mg potassium iodide to 25 mg/kg salt after an epidemiologic study in the early 1990s indicating that Slovenia was an area with mild iodine deficiency, according to the researchers.
Researchers sought to determine changes in the incidence of characteristics of iodine-induced hyperthyroidism and hypothyroidism from 2 years before to 10 years after the change in iodine concentration.
After the mandatory increase, the proportion of participants with iodine-induced hyperthyroidism decreased (P < .001), whereas the proportion of participants with iodine-induced hypothyroidism increased (P < .001). Researchers also observed increases in thyroid-stimulating hormone (P = .002), antithyroglobulin (P < .001), antithyroid peroxidase antibodies (P < .001) and the free thyroxine/free triiodothyronine ratio (P < .001), and they noted decreases in free T4 (P = .008) and free T3 (P < .001).
Antithyroid drug treatment duration (P = .001) as well as perchlorate treatment (P = .002) decreased after the mandatory increase.
“After achieving an adequate iodine supply by increasing mandatory iodization of kitchen salt, a lower incidence of [iodine-induced hyperthyroidism] can be attributed to a lower incidence of thyroid autonomy,” the researchers wrote. “The observed increase in the incidence of [iodine-induced hypothyroidism] could be related to a higher incidence of [Hashimoto’s thyroiditis]. Other beneficial clinical consequences are less severe [iodine-induced hyperthyroidism] and a shorter duration of treatment of [iodine-induced hyperthyroidism], as well as longer thyroid disease-free period in patients taking amiodarone.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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