Your body naturally makes tyrosine, a nonessential amino acid, from phenylalanine, an amino acid found in a variety of protein-rich foods, such as beef and soy 1. Proper blood levels of tyrosine aid in the production and regulation or hormones produced by the pituitary, adrenal and thyroid glands. Although tyrosine deficiency is rare, symptoms of this condition typically mimic hypothyroidism -- a condition characterized by an underactive thyroid gland.

Flu-like Symptoms

Many of the symptoms of a tyrosine deficiency are nondescript and resemble those caused by other common infections including the flu. You may feel extremely fatigued or weak and your muscles and joints may be achy, swollen or stiff. Your skin may appear unusually pale and you may not feel like participating in your usual activities. If a tyrosine deficiency is left undetected or untreated, your flu-like symptoms will become progressively more severe.

Unexplained Weight Gain

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Your thyroid hormone is responsible for regulating how quickly your metabolism the food you consume each day. An underactive thyroid produces lower than normal amounts of thyroid hormone. Without sufficient supplies of thyroid hormone, your metabolism can't function at a normal rate. For this reason, people with tyrosine deficiency may experience unexplained weight gain -- despite maintaining their normal eating routines. You may also notice that your face appears rounded or puffy due to water retention.

Poor Temperature Regulation

The level of thyroid hormone in your body also helps you maintain a constant internal body temperature, even when you're in warm or cold climates. Low levels of thyroid hormone caused by a tyrosine deficiency can lower your internal body temperature, which can increase your sensitivity to cooler temperatures. Your hands or feet may frequently feel cold to the touch or you may find that you need to dress in warmer clothing to remain comfortable throughout your normal daily activities.

Low Blood Pressure

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Your blood pressure may fall as a result of a tyrosine deficiency. People with low blood pressure levels, also called hypotension, usually don't experience noticeable symptoms. However, certain people may feel dizzy or faint or may develop blurred vision or recurrent headaches. Seek care from your doctor if these symptoms arise.

Additional Symptoms

Low tyrosine levels may also result in vocal hoarseness, dry skin, constipation, depression and brittle hair or fingernails. Women with a tyrosine deficiency may experience abnormally heavy menstrual periods due to low thyroid hormone levels.