Loading ...

Tyrosine is an unessential amino acid synthesized in the human body from another amino acid known as phenylalanine.

Tyrosine is involved in many vital processes in the body, as a result of the roles it plays in protein building and neurotransmitters production, including 3 major neurotransmitters: dopamine and catecholamine hormones, including epinephrine and norepinephrine.

More importantly, tyrosine is directly involved in the thyroid gland functions, which makes it an important amino acid for normal thyroid gland functioning, and for those suffering from certain thyroid disorders.

How can an unessential amino acid be important?

Being an unessential amino acid doesn’t really mean that tyrosine is not important; but, it means that the human body can synthesize tyrosine itself.

In contrast, other amino acids that are known as essential cannot be synthesized in the human body.

They should be obtained only from diet.

However, in many cases, people need to ensure getting sufficient amounts of tyrosine, either from diet or from dietary supplements, in order to avoid the negative effects that are likely to occur, in case of tyrosine deficiency.

Does L-tyrosine differ from tyrosine?

Actually, no.

According to stereochemistry, there are 2 theoretical isomers (forms) of tyrosine: including levorotatory and dextrorotatory.

The letter L refers to the word Levorotatory, which means that the polarized light will cause the used tyrosine to rotate anti-clockwise.

Thyroid gland functions

The thyroid gland is well-known for its functions that control many processes in the body, as shown below, though secreting the thyroid hormones, including thyroxine (T4) and triiodothyronine (T3).

Thyroid hormones secretion is regulated by the hypothalamus and pituitary gland in the brain.

In case the thyroid hormones decrease, 2 hormones are secreted by the hypothalamus and pituitary gland, including TRH and TSH, aiming at stimulating the thyroid gland to produce more hormones.

Below is a list of the functions the thyroid gland is totally or partially involved in:

• Breathing
• Cholesterol levels
• Heart rate regulation
• Central and peripheral nervous systems
• Body temperature
• Body weight
• Menstrual cycles
• Muscle strength

Importance of L-tyrosine for people with thyroid disorders

L-tyrosine supplementation is important for all individuals, especially those suffering from some symptoms and signs of thyroid disorders.

The importance of L-tyrosine administration to those people comes from L-tyrosine’s involvement in the main step of thyroid hormones production, as tyrosine is produced from the metabolism of phenylalanine, and then tyrosine is converted into thyroxine hormone, which in turn is converted into the active form of thyroid hormones, known as triiodothyronine (T3).

Sometimes, for many reason, the process of thyroid hormones production is impaired, resulting in a high need to tyrosine supplementation, such as hypothyroidism.

Hypothyroidism

Hypothyroidism means that the thyroid gland is not able to synthesize sufficient amounts of thyroid hormones, either T4 or T3, or both of them.

Many factors are likely to cause hypothyroidism, such as Hashimoto’s thyroiditis, which causes the immunity to attack the thyroid gland itself, negatively affecting its ability to work and produce the previously mentioned hormones.

As the thyroid gland is responsible for many vital functions in the body, hypothyroidism in turn can result in many signs and symptoms, which may even vary from a patient to another, and they may progress with time.

In such cases, L-tyrosine administration aims at helping the thyroid glands to overcome the insufficient amount available of phenylalanine, directly utilizing the supplied tyrosine instead, leading to improving the symptoms and signs associated with thyroid disorders.

Symptoms of hypothyroidism include sensitivity to clod, stress, feeling fatigue, weight gain, and slow mental development.

Benefits of L-tyrosine supplementation for people with thyroid disorders

People with many thyroid disorders can benefit from L-tyrosine supplementation, as shown below.

Benefits of tyrosine on phenylketonuria

Phenylketonuria is amongst the cases for which L-tyrosine supplementation can be very helpful.

Phenylketonuria occurs when the human body fails to metabolize phenylalanine amino acid, producing tyrosine.

Thus, supplementation with L-tyrosine may help keep the production rate of catecholamines within normal levels.^[1]

Benefits of tyrosine on cognition

Studies have been conducted so as to assess the effects of tyrosine on the cognitive functions.

Tyrosine supplementation could significantly improve the cognitive functions, as follows:

According to Neri DF, et al. (1995), tyrosine supplementation to individuals that remained awake for more than 24 hours has resulted in preventing the normal and expected decline in cognitive functions. Moreover, this positive effect has lasted for around 3 hours.^[2]

Benefits of tyrosine on cognition, fatigue, memory and blood pressure

In 1999, a study has been conducted so as to assess the effects of tyrosine supplementation in times of both psychological and physical stress. 21 participants of a military combat have been given tyrosine for 6 days.

The study showed that tyrosine supplementation could prevent the normal effects of both stress and fatigue, improving memory, and decreasing systolic blood pressure.^[3]

• Memory has been noted to be declined during stress. L-tyrosine administration has been noted to be able to prevent such decline, improving memory.
• According to a study of 8 participants, tyrosine supplementation could prevent the expected memory-decline effect during clod stress.^[4]

Benefits of tyrosine on fatigue and well being

Tyrosine levels were found to be lower in patients with chronic fatigue syndrome.^[5]

Another study has been conducted in mice with anorexia, and showed that tyrosine administration has resulted in many positive effects, such as improving cognition and performance.

Furthermore, the authors thought that tyrosine supplementation may improve performance, delaying the feeling of fatigue.^[6]

Benefits between tyrosine and hypothyroidism

The relationship among tyrosine and thyroid hormones has been studied, showing that levels of tyrosine significantly decreased, as a response to hypothyroidism in rats.^[7]

Sepsis

According to a study of sepsis, a relationship was noted between tyrosine, thyroid hormones and other catecholamine hormones, showing that sepsis caused tyrosine levels to decrease, leading to decreasing thyroid hormones, which is thought to result from decreasing the iodination of tyrosine, in addition to increasing catecholamine levels.^[8]

Benefits of tyrosine on stress

According to a study of mice conducted in 2012, L-tyrosine supplementation could treat all signs resulting from chronic stress, including:

• Increasing the spontaneous activity of locomotor.
• Decreasing the escape latency in the Morris water maze test
• Increasing serum levels of total thyrotropin, total triiodothyronine, and dopamine and norepinephrine.^[9]

Benefits of tyrosine on behavioral changes

L-tyrosine is sometimes suggested to help people experiencing behavioral changes resulting from stress.

Administration of 200-400 mg/kg of tyrosine in animals, around 30-60 minutes before experiencing stress, could prevent those changes.^{[10], [11], [12]}

Dosage of L-tyrosine

The common dosage of tyrosine ranges from 50-2000mg daily.

More specifically, checking studies that showed positive effectiveness of L-tyrosine administration on variety of disorders in humans, it is clear that the dosages significantly vary from a case to another.

However, the proper dosage, generally, ranges from 100 to 150mg/kg, and it should be taken around 1 hour before exposure to stress, such as workouts.

Sources of L-tyrosine

Knowing the vital benefits L-tyrosine performs, it is important to ensure keeping tyrosine within normal levels in the body, all the time.

In order to do so, people need to stick to supplements and foods containing high amounts of L-tyrosine, including:

• Whole grains, wheat, and oats.
• Fruits, such as avocados and bananas.
• Other sources include legumes, beans and nuts. Almonds and pumpkin seeds are popular choices rich in L-tyrosine.
• If you are not vegetarian, you can consider meat sources such as fish, chicken and pork, and dairy products, such as milk, cheese and yogurt.

References