Thiocyanate: a review and evaluation of the kinetics and the modes of action for thyroid hormone perturbations

Abstract

Exposure of the population to thiocyanate is predominantly through the diet and cigarette smoke. Thiocyanate is a potential thyroid disruptor due to its capacity to inhibit the uptake of iodide by the thyroid. Thiocyanate also interacts with the enzymatic reactions associated with iodide organification and thyroid hormone synthesis. Quantification of the dose-response relationships of thiocyanate and alteration in thyroid hormone levels is important for evaluating the risk of exposure to thiocyanate in humans. In this review, we highlight the key whole-body and intra-thyroidal aspects of thiocyanate kinetics in rats and its various modes of action for perturbing thyroid function. The inter-play between the various transporter- and enzyme-mediated modes of action contributes to the complexity in the dose-response relationship determinations for thiocyanate. We map the available modes of action in a mechanistic and quantitative manner. Findings summarized in this study can help support the development of a quantitative model to study the interaction effects of thiocyanate on the thyroid function. Additionally, the data gaps identified can help guide future experimental designs to characterize further thiocyanate dose-response. Finally, the strengths and weaknesses in current risk assessment considerations used for thiocyanate as a component of thyroid-active chemical mixtures are discussed.

Thyroid function disruptors: from nature to chemicals

“…Some vegetables, such as cabbage, broccoli and cassava, are a source of antithyroid compounds, such as thiocyanate and thioamides, which are well-characterized goitrogens (Gaitan 1990, Felker et al 2016, Willemin & Lumen 2017. However, the consumption of other foods and food-related compounds, such as soy protein and soybean isoflavones, as well as other flavonoids, may interfere with thyroid function.…”

The Impact of Cereal Grain Composition on the Health and Disease Outcomes

“…With mastication and ingestion, myrosinase (enzyme produced by human microflora and activated in damaged plant tissue) converts the goitrongen glucosinolates to several other compounds: nitriles, thiocyanates, sulforaphane and isothiocyanates ( 53 ). Glucosinolates could have a role in preventing cancer but also in impairing thyroid function ( 54 , 55 ). Among cereal, only millet contains a goitrogenic compounds: C-glycosylflavones which inhibit thyroid peroxidase (TPO), as shown in in-vitro models ( 19 ).…”

Is There Such a Thing as “Anti-Nutrients”? A Narrative Review of Perceived Problematic Plant Compounds

“…Despite the potential beneficial effects of glucosinolates, some evidence suggests that goitrin, produced from the glucosinolate precursor, progoitrin, as well as thiocyanate (an indole glucosinolate degradation product), may have adverse effects on the thyroid ( Table 1 ). Early animal and cell models demonstrated goitrin and thiocyanate ions to inhibit the thyroid’s utilization and uptake of iodine [ 80 , 88 , 89 ].…”