Hypothyroidism (Non-Autoimmune) is a condition characterized by reduced thyroid hormone production without autoimmune destruction of thyroid tissue. Thyroid hormones regulate cellular metabolism, mitochondrial energy production, thermogenesis, protein synthesis, cardiovascular activity, neurological signaling, gastrointestinal motility, and lipid metabolism. Reduced thyroid activity can contribute to fatigue, cold intolerance, slowed metabolism, dry skin, constipation, muscle weakness, fluid retention, slower heart rate, reduced exercise tolerance, cognitive slowing, and alterations in lipid metabolism. Non-autoimmune forms are often associated with inadequate iodine intake, selenium insufficiency, chronic oxidative stress, endocrine-disrupting environmental exposures, impaired thyroid hormone conversion, chronic inflammation, low micronutrient intake, metabolic dysfunction, elevated stress signaling, or disruption of hypothalamic-pituitary-thyroid communication. The thyroid gland depends on adequate mineral availability, antioxidant protection, amino acid supply, and balanced cellular signaling for hormone synthesis and conversion. Iodine is required for formation of thyroxine (T4) and triiodothyronine (T3), while selenium-containing enzymes support thyroid hormone activation and antioxidant defense systems within thyroid tissue. Oxidative stress may impair thyroid cellular integrity because thyroid hormone synthesis naturally generates hydrogen peroxide and reactive oxygen intermediates. Plant foods rich in polyphenols, carotenoids, flavonoids, minerals, sulfur compounds, nitrates, fiber, and antioxidant phytochemicals may help support mitochondrial efficiency, endothelial circulation, thyroid signaling balance, detoxification pathways, and cellular resilience. Whole-food plant-based dietary patterns emphasizing vegetables, legumes, fruits, herbs, seeds, mushrooms, and intact grains are associated with improved metabolic regulation, healthier inflammatory signaling, enhanced antioxidant capacity, improved insulin sensitivity, and improved vascular support. Fiber-rich foods may assist metabolic stability and gut microbiome signaling pathways linked to endocrine regulation. Green leafy vegetables, sea vegetables such as wakame, legumes, mushrooms, pumpkin seeds, Brazil nuts, lentils, quinoa, berries, citrus fruits, cruciferous vegetables, and polyphenol-rich herbs contain compounds associated with antioxidant defense systems, glutathione support, mitochondrial protection, and endocrine-supportive nutrient density. Balanced intake of selenium, iodine-containing plant foods, zinc, magnesium, iron, vitamin C, vitamin A precursors, and B vitamins contributes to thyroid hormone production, receptor signaling, mitochondrial respiration, and energy metabolism. Plant phytochemicals including quercetin, luteolin, kaempferol, sulforaphane, EGCG, curcumin, chlorogenic acid, and anthocyanins are associated with modulation of oxidative stress pathways, inflammatory signaling, and metabolic regulation connected to endocrine function.