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Levoxyl: What is it and How Does it Work?

Levoxyl: What is it and How Does it Work?

Thyroid disorders are one of the most common chronic illnesses in the United States, with an estimated 4.6 percent of Americans aged 12 and older suffering from hypothyroidism alone. Although women are much more likely to suffer from hypothyroidism than men and the elderly are also more likely to be diagnosed with the condition, people can be diagnosed with hypothyroidism at any stage of life. Patients with hypothyroidism often turn to synthetic hormone medications, such as Levoxyl, to treat their symptoms. The condition is so pervasive that nearly 102 million prescriptions were written for the generic version of Levoxyl, levothyroxine sodium, in 2017, making it one of the top three most commonly prescribed medications in the United States.  How do medications like Levoxyl work to regulate thyroid hormone levels? 

What is Levoxyl?

Levoxyl is a brand name prescription drug that is primarily used for the treatment of hypothyroidism and can also be used for the suppression of thyroid stimulating hormone. Levoxyl is sold under the generic name levothyroxine sodium; the drug was first approved by the U.S. Food and Drug Administration (FDA) in 2001. Levoxyl and its generic form are synthetic versions of T4, which is a thyroid hormone that is naturally produced by the body. Patients who do not produce enough T4 to meet their body’s needs may use Levoxyl to balance their hormone levels. Levoxyl is safe for patients of all ages, including newborns, but should be closely monitored by a healthcare provider in order to avoid dangerous side effects, particularly in children and the elderly. 

What conditions are treated with Levoxyl?

Levoxyl is primarily used for two different reasons: treatment of hypothyroidism and TSH suppression in patients with certain thyroid conditions. The two uses of the medication are discussed briefly below.

Hypothyroidism

People who do not produce enough thyroid hormones to carry out necessary bodily functions are diagnosed with hypothyroidism. The body needs thyroid hormones to help regulate a number of different functions, including assisting with digestion, regulating your metabolism,and growth and repair of the body’s cells. There are three different types of hypothyroidism, each of which is treated with Levoxyl in the same manner and each of which has the same symptoms. The three types of hypothyroidism include primary hypothyroidism, secondary hypothyroidism, and tertiary hypothyroidism, each of which have different causes. Regardless of the type of hypothyroidism a person has, Levoxyl treats hypothyroidism in the same way. Symptoms of hypothyroidism include:

  • Fatigue
  • Constipation
  • Pain, stiffness, or swelling in the joints
  • Thinning hair
  • Weight gain
  • Hoarseness
  • Elevated blood cholesterol level
  • Slowed heart rate
  • Impaired memory
  • Depression
  • Enlarged thyroid gland
  • Dry skin
  • Puffy face
  • Muscle weakness
  • Increased sensitivity to cold
  • Muscle aches, tenderness, and stiffness
  • Heavier than normal or irregular menstrual periods

TSH Suppression

In some cases, thyroid stimulating hormone, or TSH, can cause cancerous tumors to grow faster than they would otherwise. Patients with a specific type of thyroid cancer, known as thyrotropin-dependent well-differentiated thyroid cancer, need to suppress their levels of TSH in order to prevent their tumors from spreading.  Most early forms of thyroid cancer have no noticeable symptoms, but patients may experience some or all of the following symptoms as thyroid cancer progresses:

  • A lump in the throat
  • Pain in the throat and neck
  • Hoarseness
  • Difficulty swallowing
  • A cough
  • Swollen lymph nodes in the neck

How does Levoxyl work?

Levoxyl is a synthetic hormone that replaces one of the thyroid hormones naturally produced by the body. The body naturally produces two main thyroid hormones, T3 and T4. When Levoxyl is used to treat hypothyroidism, it increases the amount of T4 in the body. When the body has a sufficient amount of T4, it can begin to produce T3, which in turn helps to balance the hormone levels. Because low levels of thyroid hormones are the cause of symptoms associated with hypothyroidism, bringing these levels back into balance helps to minimize the symptoms. 

When used to treat thyrotropin-dependent well-differentiated thyroid cancer, Levoxyl works by reducing TSH levels. Patients who need to lower their TSH levels take Levoxyl because it raises the levels of other thyroid hormones in the body. When the body has a sufficient amount of thyroid hormones, it does not need to produce more TSH, as TSH is a hormone that tells the body to make more thyroid hormones. Additionally, TSH is responsible for stimulating the growth of cells in the thyroid gland. Patients who have certain types of thyroid cancer can see their tumors grow more rapidly when TSH is being produced. Therefore, keeping TSH levels suppressed by supplementing the thyroid gland with more hormones in the form of Levoxyl can help minimize the growth of certain types of cancer.

What side effects are associated with Levoxyl?

Levoxyl is associated with numerous side effects, and most of them are the result of taking too much of the medication. Patients should take exactly the amount of Levoxyl that is prescribed by their doctor at the same time each day and be sure to follow the prescribing instructions carefully. Side effects of Levoxyl that usually do not require medical attention include:

  • Abdominal or stomach cramps
  • Crying
  • Feelings of suspicion and distrust
  • Headache
  • Feeling things are not real
  • Hair loss
  • Increased appetite
  • Muscle weakness
  • Mental depression
  • Quick to react or overreact emotionally 
  • False or unusual sense of well being
  • Feeling unwell or unhappy
  • Feeling of warmth
  • Weight gain or loss
  • Change in appetite
  • Diarrhea
  • Fear or nervousness
  • Feeling of discomfort
  • Rapidly changing moods
  • Restlessness
  • Redness of the face, neck, arms, and occasionally upper chest
  • Trouble getting pregnant
  • Unusual tiredness or weakness
  • Trouble sitting still
  • Vomiting

Other side effects of Levoxyl can be serious and require immediate medical attention. If you experience any of the following side effects, it’s important to seek medical attention immediately:

  • Chest pain or discomfort
  • Difficult or labored breathing
  • Dilated neck veins
  • Irritability
  • Menstrual changes
  • Pain or discomfort in the arms, jaw, back or neck
  • Swelling of the eyes, face, lips, throat, or tongue
  • Nausea
  • Sweating
  • Tightness in the chest
  • Decreased urine output
  • Fainting
  • Fever
  • Hives or welts, skin itching, rash, or redness
  • Difficulty with swallowing
  • Extreme fatigue
  • Seizures
  • Dizziness
  • Lack or slowing of normal growth in children
  • Fast, slow, irregular, pounding, or racing heartbeat or pulse
  • Heat intolerance
  • Irregular breathing
  • Tremors
  • Blurred or double vision
  • Eye pain
  • Limp or walk favoring one leg
  • Pain in the hip or knee
  • Severe headache

While uncommon, it is possible to overdose on Levoxyl if patients take too much of the drug. Levoxyl overdose can be an emergency, so patients should seek immediate medical attention if they experience any of the following symptoms:

  • Change in consciousness
  • Sudden loss of coordination
  • Cold, clammy skin
  • Confusion
  • Fast or weak pulse
  • Lightheadedness
  • Sudden headache
  • Sudden slurring of speech
  • Loss of consciousness
  • Disorientation

Side effects associated with Levoxyl are typically the result of having an imbalance of hormones in the body as a result of taking too much or too little of the medication. Patients should not change the dose of Levoxyl they are taking without speaking to their healthcare provider first, as even a small change to the dose of the medication can cause the hormone levels in the body to change dramatically. When hormone levels are too high as a result of taking too much Levoxyl, patients tend to experience side effects associated with hyperthyroidism, including fast heart rate, feeling nervous or anxious, trouble sleeping, heart palpitations, muscle weakness, and weight loss. When patients take too little Levoxyl, side effects associated with the medication resemble the symptoms of hypothyroidism,  including tiredness, constipation, weight gain, hair loss, and muscle weakness. The best way to avoid side effects is to take your dose of Levoxyl at the same time each day and keep your dose the same unless your doctor advises you to change it.  

Sources:

https://www.mayoclinic.org/diseases-conditions/hypothyroidism/symptoms-causes/syc-20350284 

https://www.healthline.com/health/thyroid-cancer#symptoms 

https://www.webmd.com/drugs/2/drug-6137/levoxyl-oral/details 

https://www.drugs.com/levoxyl.html 

https://www.pfizermedicalinformation.com/en-us/levoxyl