Far from being an isolated system, thyroid function is intimately involved in overall wellness, and impairments impact stress resilience, immune response and cardiovascular health. Thyroid disorders range from thyrotoxicosis to thyroid cancer, with the most common being hypothyroidism. Subclinical hypothyroidism is prevalent, affects 3 to 15 percent of adults, mainly women. Symptoms of hypothyroidism are varied and non-specific, with no one symptom definitively predicting the disorder. Because weight gain, fatigue, poor concentration, depression, diffuse muscle pain, menstrual irregularities and constipation are associated with a number of conditions, thyroid dysfunction may be missed by primary care physicians. Additionally, subclinical hypothyroidism is largely asymptomatic and frequently undiagnosed and, left untreated, can progress to overt hypothyroidism.1, 2, 3, 4, 5
The traditional approach to thyroid assessment, generally aimed at diagnosing clinical thyroid disease, is lacking and limited. Standard TSH tests fail to evaluate other markers indicative of thyroid dysfunction, and emerging research suggests conventional reference ranges are outdated and excessively broad, potentially overlooking patients suffering from subclinical hypothyroidism—with troubling consequences. Untreated or inadequately treated, hypothyroidism is linked with infertility, cardiovascular disease, stroke, dyslipidemia, neurological and musculoskeletal problems and increased mortality.6, 7, 8, 9, 10
Furthermore, thyroid health is maintained by the complex interplay of multiple bodily systems. Thyroid activity is intertwined with immune response, stress resilience and cardiovascular integrity, and dysregulation in any of these systems can negatively impact thyroid status. Conversely, thyroid issues significantly affect immunity, stress perception and heart health. The intricate nature of this relationship emphasizes the importance of a personalized, integrative approach, and a growing body of research points to evidence-based botanicals and nutrients for whole-person support.11, 12, 13, 14
The HPT Axis, Stress and Thyroid Fitness.
The hypothalamic-pituitary-thyroid (HPT) axis is a crucial neuroendocrine system regulating thyroid hormone production and release, metabolic functions and various physiological processes. This feedback loop between the hypothalamus, pituitary gland and thyroid gland exists in a delicate balance, and disturbances trigger thyroid disorders and impair other systems. Chronic stress and persistently elevated cortisol levels disrupt the HPT axis, interfering with thyroid hormone synthesis and suppressing the pituitary gland’s release of TSH and potentially exacerbating autoimmune thyroid diseases, worsening symptoms and driving disease progression.15, 16, 17, 18
Adaptogens are known to influence the HPT axis and cortisol, protecting against stress-related thyroid disruption. Holy basil (Ocimum tenuiflorum) in particular is rich in bioactive compounds shown to modulate HPT axis activity, regulate cortisol production and secretion, and minimize perceived stress. In studies, holy basil supplementation was associated with lower salivary cortisol concentrations, reduced blood pressure, decreased ratings of subjective stress and improved sleep scores. In other research, holy basil significantly lessened stress-induced elevations of cortisol and alleviate symptoms in patients with generalized anxiety disorder. Holy basil also has powerful antioxidant and anti-inflammatory properties, mitigating the damaging effects of stress at a cellular level and further contributing to its benefits.19, 20, 21, 22, 23, 24
Selenium and Myo-Inositol: Nutrient Synergy for Thyroid Support.
Selenium is critical for the function of iodothyronine deiodinases, enzymes involved in regulating thyroid hormone availability and activity. Inadequate levels of selenium can impair deiodinase activity, leading to abnormal thyroid hormone metabolism and affecting T3 and other thyroid hormone metabolites, and evidence links selenium deficiency with higher rates of autoimmune thyroid disease and increased risk of mortality. Several studies have investigated the effect of selenium on thyroid disorders, with research suggesting selenium supplementation may improve thyroid hormone measures, lower antibodies and enhance quality of life for autoimmune thyroiditis patients.25, 26, 27, 28, 29, 30, 31, 32, 33
Along with selenium, myo-inositol is vital for thyroid function, regulating hydrogen peroxide (H2O2) generation, essential for iodine organification and thyroid hormone biosynthesis. Myo-inositol has been shown to improve TSH receptor sensitivity, TSH levels and thyroid antibody levels, exerting immunomodulatory activities and alleviating inflammation associated with autoimmune thyroiditis. The synergistic effect of selenium and myo-inositol is even more powerful, especially for subclinical hypothyroidism: in studies, a combination of both myo-inositol and selenium significantly decreased TSH in patients with subclinical hypothyroidism, as well as reducing TgAb better than selenium alone.34, 35, 36, 37, 38, 39
Thyroid-Immune Crosstalk and Thyroid Resilience.
The thyroid and immune systems are interconnected and bidirectional, with the immune system influencing thyroid function and thyroid hormones impacting immune responses. In the context of thyroid-immune crosstalk, NK cells, T-regulatory cells (Tregs), and immune checkpoints like ICAM-1 and VCAM-1 play crucial roles in modulating immunity and maintaining thyroid homeostasis—particularly important for autoimmune thyroid diseases. NK cells are implicated in the pathogenesis of thyroid disorders, and dysfunctional Tregs and impaired ICAM-1 and VCAM-1 interactions have been shown to contribute to the development and progression of autoimmune thyroiditis.40, 41, 42, 43, 44, 45, 46
Research suggests certain botanicals affect thyroid-immune crosstalk, immunity and thyroid health. Two of note:
- Shiitake mushrooms are a concentrated source of beta-glucans shown to directly enhance the activity of NK cells, modulate immune responses and maintain immunological tolerance. Additionally, beta-glucans have a significant effect on latent infections, known to trigger autoimmune diseases in susceptible patients. Studies report a high prevalence of common human viruses in thyroid tissue, and several viruses, including Epstein-Barr virus and cytomegalovirus, are linked with autoimmune thyroid disease.47, 48, 49, 50, 51, 52, 53
- Black cumin seed (Nigella sativa) has powerful immunomodulatory and anti-inflammatory effects and shows promise in managing Hashimoto’s and related thyroid conditions. Bioactive compounds in black cumin seed, especially thymoquinone, regulate immune response and inflammation, a key factor in Hashimoto’s, and thymoquinone’s antioxidant properties protect endocrine tissue against free radical species and contribute to hormonal rebalance. Research on patients with thyroid disorder and Hashimoto’s shows black cumin seed improves T3 and T4 levels, lowers TSH and reduces TPOAb, and animal models confirm the role of black cumin seed in reversing hypothyroidism and mitigating oxidative stress and thyroid cell damage.54, 55, 56, 57, 58, 59, 60
Vitamin D3: The Immune-Endocrine Bridge.
The immune and endocrine systems are intricately linked, engaging in bidirectional communication that impacts thyroid function and immune health. Endocrine hormones affect immune cells and cytokines, and cytokines likewise influence hormone production and HPT axis activity. This crosstalk is crucial for regulating metabolism, immunity and overall homeostasis, and vitamin D plays a prominent part in both systems. Vitamin D is known to modulate innate and adaptive immune responses, and deficiencies are associated with increased autoimmunity, impaired thyroid status and greater risk and severity of thyroid conditions. In research, low serum vitamin D levels are correlated with higher incidence of hypothyroidism, autoimmune thyroid diseases and Hashimoto’s thyroiditis compared to healthy subjects, and studies suggest vitamin D supplementation may improve thyroid function, reduce antibody levels and suppress autoimmune reactions in patients with autoimmune thyroid disorders, including Hashimoto’s and Graves’ disease.61, 62, 63, 64, 65, 66, 67, 68, 69
Thyroid Hormones and the Heart: Nutrients for Thyroid–Cardiovascular Benefits.
Thyroid hormones are engaged in a complex relationship with the cardiovascular system, influencing heart rate, vascular tone, LDL metabolism and blood pressure regulation. Research shows thyroid hormones have direct and serious effects on cardiovascular risk factors, and imbalances are implicated in heart failure, coronary artery disease, stroke and sudden cardiac death. Even mild imbalances negatively impact heart function, potentially heightening the risk of atrial fibrillation and cardiovascular mortality.70, 71, 72, 73, 74, 75, 76
Certain botanicals and nutrients are known to support cardiovascular fitness by various mechanisms. Olive leaf extract, rich in oleuropein, has positive effects on endothelial health, enhancing nitric oxide production and preventing the oxidation of LDL cholesterol, central in the development of atherosclerosis. In trials of hypertension, olive leaf extract significantly reduced both systolic and diastolic blood pressure, with some research indicating it was as effective as Captopril in patients with hypertension.77, 78, 79, 80, 81, 82
In addition to contributing to thyroid hormone production, selenium offers a dual benefit for cardiovascular health, primarily through its antioxidant properties and its incorporation into selenoproteins, essential for heart function. Research confirms selenium’s ability to protect cells from oxidative damage, influence lipid metabolism and modulate inflammation, and deficiencies are associated with higher risk of Keshan disease, atherosclerosis, myocardial infarction and heart failure.83, 84, 85, 86, 87, 88, 89
Autophagy, Cellular Health and Resilience.
As a cellular quality control mechanism, autophagy plays a vital role in both thyroid function and immune homeostasis. In thyroid follicular cells, the process of autophagy maintains cell survival and optimizes cellular performance, while in the immune system, autophagy regulates T-cell development and overall immune response. In addition to other effects, research validates the ability of specific nutrients and botanicals to inform autophagic pathways and promote cellular resilience. Black cumin seed, selenium and oleuropeins in olive leaf extract have all shown potential for influencing autophagy through various pathways including AMPK/mTOR, SIRT1 activation and other mechanisms.90, 91, 92, 93, 94, 95, 96, 97, 98
The key takeaway: the interconnectedness of stress, immune, cardiovascular and thyroid health requires a comprehensive, systems-level approach. A strategic combination of evidence-based nutrients and botanicals designed to address these systems and processes can promote thyroid resilience, restore balance and enhance whole-body wellness.
