Thyroid and adrenal health are fundamental to overall well-being, influencing metabolism, energy levels, stress response, and mood. L-tyrosine, a non-essential amino acid, emerges as a potential supporting element in the health of these vital glands. It serves as a precursor for crucial hormones and neurotransmitters involved in these physiological processes. This article explores the connection between L-tyrosine, thyroid and adrenal function, and its potential role in weight loss.
Understanding the Thyroid and Adrenal Glands
Thyroid Function
The thyroid gland, located in the neck, produces thyroxine (T4) and triiodothyronine (T3), hormones that regulate metabolism, energy production, growth, and development. Thyroid function is tightly controlled by the hypothalamic-pituitary-thyroid (HPT) axis. When the body requires more thyroid hormone, the hypothalamus releases thyrotropin-releasing hormone (TRH), which stimulates the pituitary gland to make thyroid-stimulating hormone (TSH). TSH then acts on the thyroid to stimulate the production of T4 and T3. T4 and T3 provide negative feedback to the brain, inhibiting the release of TRH and TSH to prevent excessive synthesis of thyroid hormones. Disturbances in thyroid function can lead to conditions such as hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid), impacting energy levels, weight, and mood.
Adrenal Function
The adrenal glands, situated atop each kidney, are composed of the adrenal cortex and the adrenal medulla, each producing different hormones. Adrenal dysregulation, influenced by chronic stress, can lead to HPA axis dysfunction and symptoms of adrenal fatigue. The adrenal cortex synthesizes hormones such as cortisol, aldosterone, and DHEA.
- Cortisol: A glucocorticoid hormone that metabolizes fats, proteins, and carbohydrates; dampens inflammation; increases blood sugar and blood pressure; regulates the sleep/wake cycle; and mediates the stress response. Cortisol secretion is regulated by the hypothalamic-pituitary-adrenal (HPA) axis.
- Aldosterone: A mineralocorticoid hormone that regulates blood pressure and electrolyte balance by signaling the kidneys to increase sodium reabsorption and potassium secretion.
- DHEA (dehydroepiandrosterone): A precursory androgenic hormone that is converted into testosterone and estrogens in the gonads. DHEA modulates endothelial function, reduces inflammation, improves physical strength and body composition, and enhances memory and cognition.
The adrenal medulla produces catecholamines like adrenaline (epinephrine) and noradrenaline (norepinephrine), which help the body respond to stress and contribute to the "fight or flight" response.
What is L-Tyrosine?
L-tyrosine is a non-essential amino acid, meaning the body can produce it from another amino acid called phenylalanine, or it can be obtained through dietary sources. Tyrosine is a building block for the endogenous production of dopamine, norepinephrine, and epinephrine, which are neurotransmitters involved in mood regulation, stress response, and cognitive function. In addition to its role in neurotransmitter synthesis, L-tyrosine is a precursor for the production of thyroid hormones.
Read also: Does L-Tyrosine Help with Weight Loss?
L-Tyrosine and Thyroid Health
Thyroid hormone synthesis occurs within the follicles of the thyroid gland. The thyroid gland actively transports iodine from the bloodstream into its follicular cells. Within the thyroid follicular cells, L-tyrosine is the precursor for thyroid hormones. The enzyme thyroid peroxidase (TPO) catalyzes the addition of iodine atoms to the tyrosine residues of a large glycoprotein called thyroglobulin to create monoiodotyrosine (MIT) and diiodotyrosine (DIT). Coupling reactions then combine MIT and DIT to form thyroid hormones. When one molecule of MIT combines with one molecule of DIT, the result is the formation of T3. When two molecules of DIT combine, T4 is made. Given its role in thyroid hormone production, L-tyrosine is often included in natural thyroid-supporting supplements that provide essential nutrients for thyroid hormone synthesis and conversion.
The Research on L-Tyrosine and Thyroid Hormone Production
The thyroid gland absorbs iodine, a trace mineral, from food. Then, the iodide is oxidized by thyroid peroxidase (TPO) into active iodine. Once oxidized, these iodine molecules are ready to attach to the tyrosine found in thyroglobulin (a protein produced by the thyroid gland). When iodine and tyrosine join together, they create the thyroid hormone precursors, monoiodotyrosine (T1), and diiodotyrosine (T2). T1 and T2 then combine to form thyroid hormones triiodothyronine (T3; thyroglobulin with three iodine molecules) and thyroxine (T4, thyroglobulin with four iodine molecules). T4 and T3 are the primary thyroid hormones, essential for regulating metabolic processes throughout the body.
L-Tyrosine in Adrenal Function
Catecholamines include dopamine, norepinephrine, and epinephrine, all of which are essential for various physiological functions, particularly in the nervous system and the body's response to stress. L-tyrosine serves as the precursor for the synthesis of catecholamines. Once absorbed into the bloodstream, L-tyrosine is transported to neuroendocrine chromaffin cells, densely located in the adrenal medulla, where it becomes the starting point for catecholamine production.
Within nerve cells, L-tyrosine is enzymatically converted to L-DOPA (levodopa) by the enzyme tyrosine hydroxylase. This conversion is the rate-limiting step in catecholamine synthesis. L-DOPA is converted to dopamine, a neurotransmitter involved in mood regulation, reward, and motor control. Dopamine can be converted to norepinephrine, which can be further converted to epinephrine. Recognizing L-tyrosine's central role in this cascade highlights its significance in maintaining optimal levels of catecholamines, with implications for mood regulation, stress adaptation, and various physiological functions throughout the body.
Benefits of L-Tyrosine Supplementation
Under stress, central catecholaminergic neurons are very active and require additional tyrosine to function optimally. In these acute scenarios, the body may not be able to make enough tyrosine to meet these neurons' increased demands. Some human studies suggest that tyrosine supplementation may help improve memory and cognitive function under psychological and physical stress. Small clinical studies in healthy adults show that supplemental tyrosine may support executive functioning, short-term memory, and response time compared to placebo during exposure to stressors such as cold, noise, or sleep deprivation.
Read also: The Role of L-Tyrosine in Weight Management
Working memory plays an important role in concentration and information retention. Cognitive flexibility refers to the ability to switch tasks with ease. Studies have demonstrated that tyrosine supplementation may enhance both of these parameters during mentally demanding tasks.
L-Tyrosine and Stress Response
Tyrosine serves as a precursor for the biosynthesis of neurotransmitters, specifically the “feel good” hormones, which may play a role in mitigating the negative effects of stress and supporting a balanced mood. It has a direct impact on levels of dopamine, which is the neurotransmitter that regulates the reward and pleasure centers of the brain, in addition to the adrenals that are heavily involved in the stress response.
L-Tyrosine and Mental Performance
One of the most notable benefits of tyrosine is in its ability to support cognitive performance; it’s been suggested to enhance focus and performance, as well as boost energy. During high-stress situation, tyrosine may help reduce mental fatigue and support cognitive functions, including memory.
L-Tyrosine and Mood
L-tyrosine is a precursor of several of the neurotransmitters affected by depression-including adrenaline, dopamine, and noradrenaline (NA). Two clinical studies on patients with depression and healthy volunteers show that treatment with l-tyrosine positively supports depression management.
L-Tyrosine and Cognitive Flexibility
Tyrosine increases dopamine levels in the brain and can improve mental performance in stressful situations. One clinical study asked 22 healthy adults to switch between two different tasks rapidly.
Read also: L-Tyrosine and Weight Loss
L-Tyrosine and Thyroid Function: Evidence from Animal Studies
In chronically stressed mice, spontaneous locomotor activity was significantly decreased, escape latency in the Morris water maze test was prolonged, serum levels of total thyrotropin and total triiodothyronine were significantly decreased, and dopamine and norepinephrine content in the pallium, hippocampus and hypothalamus were significantly reduced. All of these changes were suppressed, to varying degrees, by L-tyrosine supplementation.
Chronic stress causes behavioral changes and disorders in the neuroendocrine network, and L-tyrosine can relieve or inhibit these changes.
L-Tyrosine and TSH Levels
While specific studies directly linking L-tyrosine supplementation to thyroid function are limited, research on the role of tyrosine in thyroid hormone synthesis provides indirect support for considering its use in supporting thyroid health. One study did find that tyrosine supplementation improved mood and decreased TSH by 28% - markers of improved thyroid function - in subjects living in Antarctica during the winter. Other studies have found potential benefits in using tyrosine to support mood, a common concern in both thyroid and adrenal health. In this manner, tyrosine may be a natural adjunctive tool for supporting overall well-being, especially if catecholamine levels are a focus.
L-Tyrosine and Weight Loss
The Link Between L-Tyrosine, Thyroid Health, and Metabolism
This one is a biggie where weight loss is concerned and is the link between the potential for tyrosine to support weight management and body composition. The thyroid is the master metabolic regulator, and proper function of the gland is key for regulating caloric expenditure and weight. Tyrosine is required to synthesize thyroid hormones, specifically thyroxine (T4), which is the main hormone secreted by the thyroid gland.
Low levels of thyroid hormones can slow down your metabolism and change the way the body processes fat, leading to weight gain.
L-Tyrosine and Potential Weight Loss
Where weight loss is concerned, tyrosine supplementation doesn’t have much support when used alone. However, some research suggests that when combined with other fat-burning ingredients-caffeine, green tea extract, or cayenne pepper-tyrosine may help with weight loss.
L-Tyrosine and Increased Determination and Drive
Taking L-tyrosine as a supplement can help improve attention, focus, memory, motor skills, energy, and pretty much all aspects of brain function! With greater determination and drive, alongside an optimized metabolism, l-tyrosine supplements can help support you on your weight loss journey.
Recommended Dosage and Administration
Tyrosine can be obtained through the diet by eating poultry, fish, eggs, dairy, soy products, peanuts, pumpkin and sesame seeds, almonds, bananas, and avocados.
Oral tyrosine supplements are often considered in doses of 100-300 mg/kg by mouth in divided doses. In line with current research, it is advised to take a standard dose of 100-150mg per 1kg of body weight to achieve weight loss. For best results, L-tyrosine should be taken on an empty stomach in order to avoid interference from other amino acids in foods. L-tyrosine is primarily found in protein-rich animal foods, but also smaller amounts in some plant foods. Other nutrients including vitamin B6, folate, and copper are also necessary for the process of converting tyrosine into neurotransmitters.
To determine an effective and safe dose of L-tyrosine, you should always speak with a healthcare provider before taking it.
Potential Side Effects and Precautions
While tyrosine is generally safe, especially when consumed in the diet, some people may experience mild side effects to oral supplementation. Adverse reactions may include nausea, headache, fatigue, and heartburn. Tyramine, produced during the conversion of tyrosine to epinephrine, is implicated as a catalyst for migraine headaches. Individuals experiencing migraines, particularly those who have identified tyramine-rich foods as triggers, should steer clear of tyrosine supplementation.
Supplemental tyrosine has potential interactions with levodopa, a medication used in managing Parkinson's disease, and synthetic thyroid hormones. Theoretically, tyrosine might decrease the effectiveness of levodopa and increase the effects of thyroid hormone medications.
Tyrosine and levodopa compete for absorption in the proximal duodenum by the large neutral amino acid (LNAA) transport system. L-tyrosine should not be taken at the same time as L-dopa. Additionally, tyrosine is a precursor to thyroid hormones and might boost levels of thyroid hormone medication like levothyroxine and liothyronine. Tyrosine is also contraindicated with MAOI like isocarboxazid, phenelzine, tranylcypromine, and selegiline. Monoamine oxidase is the enzyme responsible for the breakdown and inactivation of the catecholamines.
People with an overactive thyroid, like hyperthyroidism or Graves' disease, should avoid tyrosine because it might affect already high thyroid hormone levels.
Rats were given doses of 0, 200, 600, or 2000 mg/kg a day to examine toxicity of L-tyrosine. Edema of the cornified layer of the forestomach was seen in 600 mg/kg supplementation in female rats and in both sexes at 2000 mg/kg day. There was increased weight and hypertrophy of hepatocytes in the liver associated with an increase in ALT and AST in both sexes when given 2000mg/kg/day of L-tyrosine. An increase of kidney weight and urinary protein was also seen at 2000 mg/kg/day. Lastly, an increase in triglycerides, total cholesterol, phospholipids, potassium ions, calcium, total protein, and alpha one globulin were seen in both sexes at 2000 mg/kg/day.
When 100 mg/kg of tyrosine is administered to humans, tyrosine decreased diastolic blood pressure. However, in another human study, tyrosine increased heart rate and blood pressure after 150 mg/kg tyrosine supplementation.
Following tyrosine supplementation of 12 g in 113 g of applesauce in adults with normal thyroid function in Antarctica during the summer, thyroid-stimulating hormone decreased by 30%. In the winter, there was a 47% improvement in mood and TSH decreased by 28% along with an increase of 6% in serum-free triiodothyronine. Additionally, 10g/day of L-tyrosine was given to patients with schizophrenia and resulted in increased saccadic intrusions.
L-tyrosine can have an effect on blood pressure, heart rate, and mood.
L-Tyrosine and Migraines
While the etiology of chronic migraine headaches is not well-understood, one hypothesis for its genesis involves abnormal metabolism of tyrosine. Tyrosine is usually metabolized into L-dopa via hydroxylation, but another pathway involving its decarboxylation can lead to build-up of trace amines such as tyramine. It is this abnormal build-up of trace amines which is suspected by some researchers to play a role in migraines. Some research has found that chronic migraine sufferers have elevated plasma levels of major products of tyrosine, including the neurotransmitters dopamine and norepinephrine, along with the trace amine tyramine. This is consistent with the hypothesis that abnormal tyrosine metabolism favoring trace amine synthesis leads to high release of these neurotransmitters, which contributes to migraines. It is possible that increased intake of L-tyrosine in migraine sufferers may fuel this process and make migraines worse, although there is currently no direct evidence substantiating this claim.
L-Tyrosine Safety
L-tyrosine is Generally Recognized as Safe (GRAS) in the USA. When L-tyrosine is used orally and short term at a dose of ≤150 mg/kg or ≤12 g per day for up to three months is generally safe.
Integrating L-Tyrosine with Other Therapeutic Approaches
Each person's needs are unique, and a holistic approach for thyroid and adrenal support considers the individual's overall health, lifestyle, and specific wellness goals. Tailoring interventions to address the root causes of thyroid and adrenal concerns is fundamental. While L-tyrosine supplementation can be a valuable component of a wellness plan, it should be integrated with other strategies that focus on the underlying factors of endocrine health.
Adopting a balanced diet rich in nutrients that support thyroid and adrenal function is fundamental. In addition to eating tyrosine-rich foods, including foods high in iodine, selenium, magnesium, zinc, vitamin D, and B vitamins can be beneficial in providing additional cofactors required for optimal thyroid and adrenal functioning.
Chronic stress is not only a primary contributor to adrenal fatigue, but it can also affect TSH and lead to thyroid concerns. Managing stress, therefore, is crucial for adrenal and thyroid health. Mind-body techniques like meditation, deep breathing, and yoga can help reorient to stressors and mitigate stress levels. Adequate sleep and maintaining a healthy sleep-wake cycle are also vital for adrenal and thyroid function.
Depending on the specific thyroid or adrenal concern, conventional medical approaches may include hormone replacement therapy, medication to support hormone levels, or surgical interventions in some instances. L-tyrosine supplementation can sometimes be an adjunctive tool alongside conventional approaches, but it's essential to consult healthcare professionals for personalized guidance.