Citomegalovirus

Anchovies are an important dietary source of selenium, a cofactor for iodothyronine deiodinase enzymes that activate thyroid hormones (converting T4 to T3). WebMD cites a 1990s study identifying selenium as part of a thyroid-activating enzyme, and additional research links selenium deficiency to thyroid dysfunction.

Ashwagandha (Withania somnifera) root extract has been shown in a randomized controlled trial to normalize serum T3, T4, and TSH in subjects with subclinical hypothyroidism. Active withanolide glycosides are thought to stimulate thyroid secretory function via the hypothalamic-pituitary-thyroid axis. It is also traditionally recommended in Ayurvedic medicine for thyroid imbalances.

Bovine kidney is a concentrated dietary source of selenium, which is an obligatory cofactor for type I iodothyronine deiodinase—the selenoprotein enzyme that converts inactive T4 into active T3. Selenium deficiency is associated with autoimmune thyroid disease, including Hashimoto's thyroiditis and Graves' disease. Multiple clinical studies support selenium supplementation in thyroid autoimmunity.

A peer-reviewed rodent study (PMC3410357) showed B. falcatum aqueous extract dose-dependently reversed LT4-induced hyperthyroidism in rats, normalizing T3, T4, and TSH levels, and protecting the thyroid gland histopathologically. These effects were compared favorably to propylthiouracil. Evidence is preclinical only.

Coleus forskohlii contains forskolin, a direct activator of adenylate cyclase that mimics TSH signaling in thyroid follicles. In isolated thyroid tissue and animal models, forskolin stimulates T3 and T4 secretion and increases iodide uptake and thyroid peroxidase activity. No adequately powered human RCT has evaluated forskolin specifically for thyroid endpoints.

Copper is recognized among essential trace minerals for thyroid function in peer-reviewed nutritional reviews. Cross-sectional studies show copper levels correlate with FT4 and TSH. Copper is required for the function of enzymes involved in thyroid hormone metabolism and immune regulation relevant to autoimmune thyroid disease.

Diiodotyrosine (DIT) is an endogenous intermediate in thyroid hormone biosynthesis, formed when two iodine atoms are added to tyrosine residues on thyroglobulin. Two DIT molecules couple to form thyroxine (T4). It is included in some thyroid support supplement formulas and has been used clinically as a nutritional adjunct for thyroid support.

Guggul (Commiphora mukul) resin contains Z-guggulsterone, a ketosteroid that has shown thyroid-stimulatory activity in animal studies, increasing thyroid iodine uptake, thyroid peroxidase activity, and T4-to-T3 conversion. It is used in Ayurvedic medicine as a thyroid stimulant. Robust human clinical trials for thyroid endpoints are lacking.

Guggulsterones are the principal bioactive ketosteroids of Commiphora mukul resin. Z-guggulsterone has demonstrated direct thyroid-stimulatory action in animal studies, increasing thyroid iodine uptake, thyroid peroxidase activity, and T4-to-T3 conversion. They are used in formulations targeting subclinical hypothyroidism and metabolic support.

Iodine is the essential raw material for thyroid hormone synthesis; T3 and T4 each contain iodine atoms incorporated into tyrosine residues on thyroglobulin. Deficiency causes goiter, hypothyroidism, and—in severe cases—cretinism. Thyroid function follows a nonlinear relationship with iodine intake, where both deficiency and excess can impair function.

Iron is a critical cofactor for thyroid peroxidase (TPO), the heme-containing enzyme that catalyzes the iodination of tyrosine residues to form thyroid hormones. Iron deficiency reduces TPO activity, impairs T4-to-T3 conversion, and raises TSH. Clinical trials show concurrent iron and iodine supplementation in iron-deficient goitrous children reduces goiter prevalence more than iodine alone.

L-phenylalanine is an indirect but essential biochemical contributor to thyroid hormone synthesis. It is converted to tyrosine, which is then iodinated within thyroglobulin to produce T3 and T4. Adequate phenylalanine availability is therefore necessary for normal thyroid hormone production, though no clinical trials specifically supplement L-Phe for thyroid conditions.

L-tyrosine is the direct biosynthetic precursor to thyroid hormones T3 and T4. Within the thyroid gland, tyrosine residues on thyroglobulin are iodinated and coupled to form T3 and T4, making tyrosine availability a prerequisite for hormone synthesis. While mechanistic data strongly support this role, no large well-designed RCTs have confirmed supplemental L-tyrosine as a clinical treatment for hypothyroidism.

Magnesium is listed among key micronutrients influencing thyroid hormone synthesis and regulation. A 10-week RCT demonstrated that combined zinc, vitamin A, and magnesium supplementation significantly raised FT4 in hypothyroid patients. Magnesium deficiency has been associated with thyroid dysfunction, and supplementation may have a protective role against thyroid disorders.

Manganese participates in the synthesis of thyroxine and is required for normal thyroid function; deficiency may contribute to hypothyroid conditions. Excess manganese intake may conversely interfere with thyroid hormone production.

Scrophularia root has documented traditional use for goitre and thyroid-related swellings in TCM, and modern pharmacological studies have specifically investigated its effects on hyperthyroidism. A metabolomics and network pharmacology study in rats identified hyperthyroidism treatment potential via modulation of the HIF and IL-6/APOA1/cholesterol signalling pathways.

Selenium is incorporated into selenoproteins essential for thyroid function, including the three iodothyronine deiodinases (DIO1, DIO2, DIO3) that convert prohormone T4 to active T3, and glutathione peroxidases that protect thyroid tissue from oxidative damage. The thyroid contains the highest selenium concentration per gram of any human tissue. Selenium supplementation reduces thyroid peroxidase antibodies in Hashimoto's thyroiditis.

Selenomethionine is the primary organic form of selenium used in supplements and is the most bioavailable form studied in clinical trials for thyroid health. It serves as the selenium source incorporated into selenoproteins, including the deiodinases required for T4-to-T3 conversion. RCTs using selenomethionine have demonstrated reductions in thyroid peroxidase antibodies in Hashimoto's thyroiditis.

Vitamin A influences thyroid hormone metabolism and is included among key micronutrients affecting thyroid function in peer-reviewed nutritional reviews. It may have a role in modulating autoimmune thyroid disease, and combined supplementation with zinc and magnesium (including vitamin A) has improved thyroid hormone levels in RCTs. The main mechanism involves thyroid hormone receptor regulation.

Vitamin B12 is recognized as important to thyroid function; deficiency is co-prevalent with hypothyroidism and Hashimoto's thyroiditis, and deficiency contributes to autoimmune thyroid disease through immune dysfunction. A 2023 systematic review and meta-analysis confirmed associations between B12 levels and thyroid disorders. Adequate B12 status is considered supportive of optimal thyroid health.

Vitamin D deficiency is considered a risk factor for autoimmune thyroid diseases including Hashimoto's thyroiditis and Graves' disease, and for thyroid cancer. Multiple studies show a negative association between serum 25(OH)D and anti-thyroid antibodies. Clinical studies of vitamin D supplementation in Hashimoto's patients consistently show reductions in anti-thyroid antibody levels.

Zinc plays a key regulatory role in thyroid hormone metabolism by modulating deiodinase enzyme activity, TRH and TSH synthesis, and thyroid hormone receptor binding. Clinical studies show zinc supplementation improves FT3 and FT4 levels in zinc-deficient hypothyroid patients. Zinc transporters are expressed in the hypothalamus, pituitary, and thyroid gland.

Bacopa monnieri extract has been shown in animal studies to elevate T4 levels (by 41% in one rat study) and is used in Ayurvedic medicine as part of formulations supporting thyroid health. Its traditional Ayurvedic use for metabolic and cognitive conditions overlaps with thyroid support, though human clinical trials specifically for thyroid endpoints are lacking.

Bladderwrack (Fucus vesiculosus), a brown seaweed, has been used in traditional folk medicine for centuries to treat goiter and thyroid disorders, primarily because of its natural iodine content. It has been used for both hypothyroidism and hyperthyroidism, though modern clinical trial evidence is lacking and effects depend heavily on iodine status.

Bugleweed (Lycopus virginicus and related Lycopus species) has been used in traditional herbal medicine to reduce thyroid activity in hyperthyroidism. Extracts have been shown in some studies to inhibit TSH binding, reduce thyroid hormone synthesis, and decrease prolactin. It is primarily used in naturopathic practice for mild hyperthyroidism and Graves' disease.

Guggulsterone from Commiphora mukul has been shown in animal and in vitro studies to stimulate thyroid function by enhancing iodine uptake and thyroid peroxidase activity. Traditional Ayurvedic use for obesity included thyroid stimulation as a proposed mechanism. Human RCT evidence is absent.

Dulse has been used traditionally as a dietary source of iodine to support thyroid function, particularly in iodine-deficient coastal populations of Ireland, Scotland, and Atlantic Canada. Iodine is essential for synthesis of thyroid hormones T3 and T4. A human RCT with dulse-enriched bread observed changes in TSH (thyroid-stimulating hormone) that remained within the normal clinical range. Direct clinical evidence for dulse-specific thyroid benefit is lacking.

Kelp (Laminaria spp.) is a brown seaweed traditionally used as a dietary source of iodine to support thyroid function and prevent goiter. Like bladderwrack, its thyroid relevance is primarily via iodine content, which varies widely. Clinical evidence is limited, and excessive intake can paradoxically impair thyroid function.

Lemon balm (Melissa officinalis) has been studied for anti-thyroid activity relevant to hyperthyroidism. Rosmarinic acid in lemon balm inhibits TSH binding to thyroid receptors and reduces thyroid hormone synthesis in preclinical studies. It is used in European herbal medicine for thyroid overactivity and Graves' disease, with the German Commission E acknowledging its use.

Pituitary substance has traditionally been used to support thyroid health via the pituitary's production of TSH, which governs thyroid hormone synthesis. Naturopathic and integrative practitioners include pituitary glandular in protocols for transient pituitary-thyroid dysfunction. No modern clinical trials support this use.