Which of the following compounds are environmental goitrogens linked to hypothyroidism?

• A. Fluoride, mercury, perchlorate
• B. Iodine deficiency
• C. Selenium deficiency
• D. Vitamin D deficiency

Answer: (A)

Goitrogens are substances that disrupt thyroid function by interfering with iodine uptake or thyroid hormone synthesis, which can lead to hypothyroidism and a goiter. Perchlorate directly blocks the sodium-iodide symporter in the thyroid, reducing iodine uptake and hormone production. Fluoride, at higher environmental exposures, has been associated with thyroid disruption and can contribute to lowered thyroid function in susceptible individuals. Mercury can interfere with thyroid hormone synthesis and metabolism by affecting selenium-dependent enzymes and other parts of the thyroid axis.

Iodine deficiency is a nutritional lack of the substrate needed to make thyroid hormones, not an environmental goitrogen. Selenium deficiency affects the conversion of T4 to the active T3 but is not a direct environmental goitrogen. Vitamin D deficiency is not linked to thyroid hormone production.

Thus, the environmental goitrogens linked to hypothyroidism in this context are fluoride, mercury, and perchlorate.