Thyroid hormones are the hormones of longevity & vitality. Their role in metabolic regulation, cardiovascular health, cognitive function, muscle strength, bone health, mood regulation, and cellular regeneration collectively contribute to a sense of well-being & optimal functioning all through life and in particular as we age.

The sweet spot of optimal thyroid function is beneficial and both hypo- and hyperthyroidism can lead to health issues. Hypothyroidism can result in fatigue, weight gain, and other metabolic disturbances, while hyperthyroidism can cause heart palpitations, anxiety, and weight loss.

It is worthwhile noting that you don’t need to have clinical hypo- and hyperthyroidism to experience negative impacts on your health. In fact, even if your thyroid numbers fall within the "normal" range, being outside of the "optimal range" can still affect your health & performance negatively.

For instance, variations in thyroid function within the reference ranges are linked to different risks of cardiovascular issues like atrial fibrillation, stroke, sudden cardiac death, and heart-related mortality.

To illustrate the wide-ranging impact of thyroid hormones, here are some examples of how they influence various bodily processes:

• Reproductive Function: Women: Thyroid hormones exert influence on female reproductive health. They can impact the menstrual cycle and fertility. Hypothyroidism, can lead to irregular or absent menstrual periods, while hyperthyroidism, with elevated thyroid hormone levels, result in shorter menstrual cycles. These disruptions occur due to the thyroid hormones’ effect on the release of key hormones. Thyroid hormones influence the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus, which in turn affects the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland. These interactions are involved in regulating the menstrual cycle, ovulation, and overall fertility in women.
• Reproductive Health: Men: Thyroid hormones also affect male reproductive health, particularly in testosterone production. These hormones influence the hypothalamic-pituitary-testicular axis. By regulating the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), thyroid hormones influence the Leydig cells in the testes, which are responsible for producing testosterone. Disruptions in thyroid function, especially in cases of hypothyroidism, can lead to decreased testosterone production in men. This reduction in testosterone levels can impact bedroom performance, function and fertility. Maintaining a balanced thyroid function is essential to ensure proper hormone interactions and support optimal reproductive health in both men and women.
• Muscle Strength and Bone Health: Thyroid hormones affect musculoskeletal health through multiple pathways. T3 stimulates the synthesis of contractile proteins in muscles. This promotes muscle growth and strength. In bones, thyroid hormones influence osteoblast and osteoclast activity. T3 enhances osteoblast differentiation and collagen synthesis, promoting bone formation. Simultaneously, it modulates the receptor activator of nuclear factor kappa-B ligand (RANKL), regulating osteoclast-mediated bone resorption. Thyroid therefore promotes & preserves physical vitality through maintaining bone density and muscle strength.

• Cellular Regeneration: Thyroid hormones regulate cell proliferation, differentiation, and apoptosis. T3 enhances the expression of growth factors like insulin-like growth factor 1 (IGF-1) and epidermal growth factor (EGF), promoting tissue repair and regeneration. It also affects extracellular matrix components to support tissue integrity. In addition, T3 aids in maintaining skin hydration and elasticity by upregulating hyaluronic acid synthesis. These mechanisms collectively contribute to cellular vitality and youthful tissue appearance.
• Metabolic Regulation: Thyroid hormones, primarily T3, are regulators of the basal metabolic rate (BMR). They enhance the expression of genes involved in energy production & consumption. In mitochondria, T3 stimulates the activity of enzymes like cytochrome c oxidase, boosting the electron transport chain and ATP production. The increased metabolic activity leads to increased heat production & energy expenditure, assisting with efficient nutrient utilization. Therefore, optimal thyroid function maintains a balanced metabolism, counteracting age-related metabolic decline.
• Cardiovascular Health: Thyroid hormones, particularly triiodothyronine (T3), enhance cardiac contractility by upregulating calcium handling proteins in cardiac muscle cells, leading to increased heart rate and stroke volume. Additionally, T3 promotes vasodilation through endothelial nitric oxide synthase (eNOS) activation, optimizing blood vessel function. This dual effect leads to better heart function, efficient blood circulation, and optimized blood pressure regulation.
• Cognitive Function: Thyroid hormones also affect brain development and cognitive function. T3 modulates the expression of brain-derived neurotrophic factor (BDNF), a protein that supports neuronal growth, differentiation, and synaptic plasticity. T3 also affects the myelination of nerve fibers, ensuring efficient neural transmission. Furthermore, T3 influences the production of neurotransmitters like serotonin and dopamine and receptor sensitivity, essential for mood and cognitive processes. Thyroid hormones foster cognitive vitality through enhancing memory, focus and regulating mood.

• Mood Regulation: Thyroid hormones influence mood by affecting neurotransmitter synthesis and signaling. T3 regulates the transcription of the tryptophan hydroxylase gene, an enzyme in serotonin production. It also modulates expression of dopamine receptors & transporters. Proper thyroid function ensures optimal levels of serotonin and dopamine, supporting mood stability. Additionally, T3’s impact on the hypothalamic-pituitary-adrenal (HPA) axis helps regulate stress response, further contributing to emotional vitality.
• Temperature Regulation: Thyroid hormones facilitate thermogenesis, the process of heat production. T3 increases the expression of uncoupling proteins (UCPs) in mitochondria, leading to uncoupled oxidative phosphorylation. This process dissipates energy as heat, contributing to temperature regulation in the body. Furthermore, T3 stimulates blood flow to the skin through vasodilation, facilitating heat dissipation. By maintaining optimal body temperature, thyroid hormones help support enzymatic activities for physiological processes.
• Gastrointestinal Function: Thyroid hormones influence gastrointestinal motility and nutrient absorption. Specifically, T3 enhances the expression of digestive enzymes, promoting efficient nutrient breakdown. It also accelerates intestinal transit by modulating smooth muscle contraction, preventing constipation. T3’s impact on enteric nervous system function helps with proper gut motility. These actions optimize nutrient absorption, energy utilization, and overall gastrointestinal function.

By understanding these intricate physiological mechanisms, we gain a deeper appreciation for how thyroid hormones contribute to longevity & vitality across various bodily systems.

In the upcoming Thyroid Series - I will cover:

• Blood markers for thyroid function & what they mean
• The optimal thyroid ranges
• Everyday signs of poor thyroid function & dysfunction
• Autoimmune thyroid conditions
• Nutritional, environmental, other lifestyle factors affecting your thyroid health

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​BTW, recently, I shared my Longevity Supplement stack. If you have missed it, you can read about it here:​

​Supplements - My Age-better Longevity Stack​ ​ I am often asked what supplements I consider best for ‘longevity’... Read article

Disclaimer

This information is not medical advice. This content and other content on this website is for informational and educational purposes only and is not intended to be a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

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References

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