Single and multiple selenium-zinc-iodine deficiencies affect rat thyroid metabolism and ultrastructure

Area of Science:

• Endocrinology
• Nutritional Science
• Toxicology

Background:

• Thyroid function is crucial for metabolism and development.
• Trace minerals like selenium (Se), zinc (Zn), and iodine (I) are essential for thyroid hormone synthesis and metabolism.
• Understanding the interplay of these nutrient deficiencies is vital for public health.

Purpose of the Study:

• To investigate the individual and combined effects of Se, Zn, and I deficiencies on rat thyroid function.
• To assess the impact on thyroid hormone levels, thyroid-stimulating hormone (TSH), and thyroid enzyme activity.
• To examine structural changes in thyroid tissue under different deficiency conditions.

Main Methods:

• Rats were fed controlled amino acid-based diets with varying levels of Se, Zn, and I for 6 weeks post-weaning.
• Seven experimental groups were established: single, double, and triple deficiencies (Se-, I-, Zn-, Se-I-, Zn-I-, Se-Zn, Se-I-Zn-).
• Serum hormone levels (T3, T4, free T4, TSH), thyroid glutathione peroxidase activity, and thyroid histology were analyzed.

Main Results:

• Iodine deficiency significantly lowered total T4, free T4, and increased TSH in all affected groups.
• Selenium and/or zinc deficiencies reduced serum T3 and thyroid glutathione peroxidase activity.
• Thyroid follicle architecture was severely altered in Zn- and Se-Zn-deficient groups, with less severe changes when iodine was also deficient.

Conclusions:

• Single and combined deficiencies of Se, Zn, and I exert distinct and significant effects on thyroid hormone regulation and thyroid gland morphology.
• Iodine status plays a critical role in modulating the effects of Se and Zn deficiencies on thyroid function.
• These findings highlight the complex interactions between essential trace elements in maintaining thyroid homeostasis.