L-Tyrosine is an amino acid that serves as a precursor to several important neurotransmitters, including dopamine, norepinephrine, and epinephrine. It is also involved in the production of thyroid hormones. As an essential component for these biochemical pathways, L-Tyrosine plays a role in various physiological functions, including stress response, mood regulation, and cognitive processes. The body can synthesize L-Tyrosine from another amino acid, phenylalanine, but it can also be obtained through dietary sources or supplements. Due to its involvement in neurotransmitter and hormone synthesis, L-Tyrosine has been investigated for its potential effects on conditions related to stress, mood, and thyroid function.

Quick answer

What it is: L-Tyrosine is an amino acid that serves as a precursor to several important neurotransmitters, including dopamine, norepinephrine, and epinephrine.

May support:Primary Hypothyroidism, Hypothyroidism, Thyroid Disorders, Subclinical Hypothyroidism, Adrenal Fatigue

Evidence:Evidence · Grade D

Evidence Summary

Evidence · Grade D

The current evidence for L-Tyrosine's efficacy in specific health conditions, particularly those listed, is primarily based on its known biochemical role as a precursor. The provided reference is a general fact sheet, not a clinical trial, and therefore does not offer direct evidence of therapeutic efficacy for specific ailments. More robust human clinical trials are needed to establish definitive benefits.

Last reviewed · Jun 2026

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What did you try it for?

Your experience for Primary Hypothyroidism:

Related conditions

Primary Hypothyroidism Hypothyroidism Thyroid Disorders Subclinical Hypothyroidism Adrenal Fatigue

Linked nutrient deficiencies

Vitamin and mineral deficiencies commonly associated with the conditions this remedy may support.

Iodine

Trace mineral

Building block of thyroid hormones T3 and T4.

Protocol· NIH Office of Dietary Supplements

Linked to Hypothyroidism

Both deficiency and excess affect the thyroid. In Hashimoto's, supplementation should be cautious; in hypothyroidism from low intake it is essential.

Common symptoms

Goiter
Fatigue
Cold intolerance
Weight gain
Dry skin
Brain fog

Food sources

Seaweed (kelp, nori, wakame)
Iodized salt
Cod and haddock
Dairy
Eggs

Lab markers to discuss

Urinary iodine concentration (UIC, spot test)
TSH

Reference intake: 150 mcg/day adults; 220 mcg pregnancy.

Supplementation notes: In autoimmune thyroid disease, work with a clinician — high doses can worsen Hashimoto's.

Why it matters here

Hypothyroidism: Iodine is the substrate for thyroid hormone — deficiency causes goiter and hypothyroidism.

Selenium

Trace mineral

Essential for thyroid hormone metabolism and antioxidant defense (glutathione peroxidase).

Protocol· NIH Office of Dietary Supplements

Linked to Hypothyroidism

Selenium reduces TPO antibodies in Hashimoto's and supports T4→T3 conversion. Deficiency is implicated in thyroid autoimmunity and viral susceptibility.

Common symptoms

Thyroid dysfunction
Frequent infections
Brain fog
Hair loss
Muscle weakness

Food sources

Brazil nuts (1–2/day)
Sardines, tuna
Eggs
Sunflower seeds
Grass-fed beef

Lab markers to discuss

Serum or plasma selenium
Erythrocyte glutathione peroxidase

Reference intake: 55 mcg/day RDA; therapeutic 200 mcg/day studied for Hashimoto's.

Supplementation notes: Do not exceed 400 mcg/day long-term — selenium toxicity causes hair/nail loss.

Why it matters here

Hypothyroidism: Selenoenzymes convert T4 to active T3.

Iron (Ferritin)

Mineral

Required for oxygen transport, thyroid hormone conversion, and energy production.

Protocol· NIH Office of Dietary Supplements

Linked to Hypothyroidism

Low ferritin (iron stores) is a frequent driver of fatigue, hair loss, restless legs, and impaired T4→T3 conversion in hypothyroidism and Hashimoto's.

Common symptoms

Fatigue, exhaustion
Hair shedding
Pale skin
Restless legs
Cold hands/feet
Brittle nails

Food sources

Red meat and liver
Oysters and clams
Lentils and beans
Pumpkin seeds
Spinach (with vitamin C)

Lab markers to discuss

Ferritin (functional target 70–100 ng/mL for women, 100+ for hair/thyroid)
Serum iron
TIBC
Transferrin saturation

Reference intake: 8 mg/day men, 18 mg/day premenopausal women.

Supplementation notes: Take iron with vitamin C; avoid with coffee, tea, or calcium. Bisglycinate is gentler on the gut than ferrous sulfate.

Why it matters here

Hypothyroidism: Low ferritin impairs T4→T3 conversion and worsens fatigue.

Zinc

Trace mineral

Required for immune function, wound healing, skin integrity, and thyroid hormone synthesis.

Protocol· NIH Office of Dietary Supplements

Linked to Hypothyroidism

Low zinc is linked to recurrent infections, acne, slow wound healing, leaky gut, and impaired taste/smell. Often deficient in vegetarians and those with gut malabsorption.

Common symptoms

Frequent colds/infections
Acne or slow-healing skin
Loss of taste or smell
Hair loss
White spots on nails

Food sources

Oysters
Beef and lamb
Pumpkin seeds
Cashews
Lentils and chickpeas

Lab markers to discuss

Plasma or serum zinc
Zinc/copper ratio

Reference intake: 8–11 mg/day RDA.

Supplementation notes: Take away from iron and calcium. Long-term high-dose zinc depletes copper — pair with ~1 mg copper if dosing >30 mg/day.

Why it matters here

Hypothyroidism: Zinc supports TSH and thyroid hormone production.

Vitamin D

Fat-soluble vitamin

Hormone-like vitamin central to immune function, mood, bone, and thyroid health.

Protocol· NIH Office of Dietary Supplements

Linked to Hypothyroidism

Low vitamin D status is one of the most widespread deficiencies globally and has been linked to autoimmune disease activity (Hashimoto's, MS), mood disorders, recurrent infections, and poor skin barrier function.

Common symptoms

Fatigue
Low mood
Frequent infections
Bone or muscle aches
Hair thinning

Food sources

Fatty fish (salmon, sardines)
Egg yolks
Cod liver oil
UV-exposed mushrooms
Fortified dairy

Lab markers to discuss

25-hydroxyvitamin D (target 40–60 ng/mL per most functional ranges)

Reference intake: Adults 600–800 IU/day RDA; functional medicine often targets 2,000–5,000 IU/day with monitoring.

Supplementation notes: Take with a fat-containing meal. Pair with vitamin K2 (MK-7) when supplementing higher doses long-term.

Why it matters here

Hypothyroidism: Frequently low in hypothyroid patients; influences immune tolerance.

Community Discussions

What people say about L-Tyrosine

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Latest news on L-Tyrosine

Health videos on L-Tyrosine

Why It Works

L-Tyrosine is a direct precursor to catecholamine neurotransmitters (dopamine, norepinephrine, epinephrine) and thyroid hormones, influencing their synthesis.

How it works in more detail

L-Tyrosine is hydroxylated to L-DOPA by tyrosine hydroxylase, which is then decarboxylated to dopamine. Dopamine can be further converted to norepinephrine and then epinephrine. In the thyroid gland, L-Tyrosine is iodinated to form monoiodotyrosine (MIT) and diiodotyrosine (DIT), which are then coupled to form thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3). These pathways highlight L-Tyrosine's fundamental role in both neural and endocrine signaling.

How to use

Always consult a qualified clinician.

Editorial guidance

Typical forms

capsule, powder

Community tips

No community tips yet — be the first to share what worked for you.

Safety

Safety warnings

While generally recognized as safe, individuals with certain medical conditions, particularly those affecting thyroid function or neurotransmitter balance, should consult a healthcare professional before taking L-Tyrosine supplements. The provided fact sheet does not detail specific safety concerns or contraindications.

General guidance — discuss specifics with a clinician.

Evidence ecosystem

Scientific literature, clinical guidance, government sources, ongoing research, traditional use, and lived experience — grouped by source type and quality.

Overall grade (D)

The current evidence for L-Tyrosine's efficacy in specific health conditions, particularly those listed, is primarily based on its known biochemical role as a precursor. The provided reference is a general fact sheet, not a clinical trial, and therefore does not offer direct evidence of therapeutic efficacy for specific ailments. More robust human clinical trials are needed to establish definitive benefits.

Filter by source type

Government Health Sources(1)

Public-health agencies: NCCIH, NIH, CDC, NHS.

High Quality

Dietary Supplement Fact Sheets
NIH Office of Dietary Supplements (ODS)
The ODS provides comprehensive fact sheets on individual vitamins, minerals, and other dietary supplements. While there isn't a specific L-Tyrosine for Thyroid fact sheet, general information on L-Tyrosine and its known physiological roles and interactions would be covered here.
Government SourceNIH Office of Dietary Supplements (ODS)High Quality

Clinical Trial Registries(1)

Registered ongoing or completed trials (ClinicalTrials.gov).

Moderate Quality

A Randomized, Double-Blind, Placebo-Controlled Clinical Trial to Evaluate the Efficacy of a Zinc, Selenium, and L-Tyrosine Supplement in the Prevention of Thyrotoxicosis in Subjects With r25191G/A SEPP1 Polymorphism
n=150 · NCT06264544 · NOT_YET_RECRUITING · NOT_YET_RECRUITING
This randomized, double-blind, placebo-controlled trial evaluates the efficacy of a zinc, selenium, and L-tyrosine supplement in preventing thyrotoxicosis among adults aged 18-85 with elevated TPOAb levels and the r25191G/A SEPP1 polymorphism. The study excludes those with thyroid disease, pregnant/breastfeeding women, and individuals allergic to the supplement. Key endpoints include changes in thyroid antibodies and hormones over a 6-month period. With an estimated sample size of 150 participants per group, accounting for a 20% dropout rate, the trial seeks to demonstrate the supplement's potential in reducing thyrotoxicosis risk through a genetically-informed approach.
Clinical TrialClinicalTrials.govModerate Quality

Limitations: The primary limitation is the lack of specific human clinical trials directly investigating L-Tyrosine for conditions like Primary Hypothyroidism, Hypothyroidism, Thyroid Disorders, Subclinical Hypothyroidism, or Adrenal Fatigue. The available information describes its biochemical role rather than clinical outcomes.

L-Tyrosine

Quick answer

Evidence Summary

Have you tried L-Tyrosine?

Commonly Combined With

Community signal breakdown

People Like Me insights

What people say about L-Tyrosine

Latest news on L-Tyrosine

Health videos on L-Tyrosine

Why It Works

How it works in more detail

How to use

Safety

Evidence ecosystem

Government Health Sources(1)

Clinical Trial Registries(1)