Levothyroxine is a synthetic hormone of the thyroid glandule. It can be used as a drug for thyroid insufficiency replacement to treat hypothyroidism (condition with low level of the thyroid hormones). Also Levothyroxine is used for the treatment of the congenital hypothyroidism (cretinism) and certain thyroid cancers types and it can be prescribed to prevent or decrease goiter (enlargement of the thyroid glandule).
Levothyroxine shouldn’t be used for other purposes (e.g. for treatment of the obesity or infertility if it is not caused by low level of the thyroid hormones)
Side effects
Levothyroxine is usually well tolerated and patients can take it during years. But some people can experience side effects more often than not due to overdose.
The most widespread side effect of the Levothyroxine is hyperthyroidism (syndrome with excess of the thyroid hormones). Symptoms of such medically induced hyperthyroidism include:
- Tachycardia (high heart rate)
- Mood changes
- Hyperactivity
- Nervousness
- Irritability
- Anxiety
- Tremor
- Feeling hot
- Increased sweating
- Flushing
- Fever
- An increased appetite, along with weight loss
- Muscle weakness
- Vomiting
- Diarrhea
- Stomach cramps
- Difficult or painful breathing
- High blood pressure
- Heart palpitations
- Chest pain
- Insomnia
- Hair loss
- Menstrual problems
- Seizures
If you experience any of these symptoms call you health provider to determine its source and adjust the Levothyroxine’s dose.
Other side effects of the Levothyroxine are:
- Fatigue
- Severe or persistent headache
- Heat intolerance
- Excessive sweating
- Changes in appetite (increased appetite or anorexia)
- Nausea
- Vomiting
- Stomach cramps
- Diarrhea (sometimes severe)
- Fever
- Joint pain
- Lowing bone mineral density (especially in women)
- Leg cramps
- Muscle weakness
- Seizures
- Tremors
- Shortness of breath
- Chest pain
- Arrhythmia (fast or irregular heartbeat)
- Increased left ventricular mass index
- Enhanced left ventricular systolic function
- Trouble sleeping
- Anxiety
- Irritability
- Nervousness
- Unusual weight gain
- Weight loss
- Changes in menstrual periods
Also as any other medicine Levothyroxine can cause an allergic reaction. This can manifest in:
- Dizziness
- Difficulty breathing
- Wheezing (unusual hoarseness)
- Flushing
- An unexplained rash
- Urticaria
- Hives
- Itching
- Unexplained swelling (especially of the face, lips, mouth, tongue or throat and neck)
- Angioedema
- Serum sickness.
Serious side effects:
Serious adverse effects usually develop due to hyperthyroidism. They can include: angina pectoris, arrhythmias (premature ventricular beats), heart failure, heart attack, heart arrest, osteoporosis, broken bones (femur fractures in males) or other signs of weakened bones (due to lowing of the bone density), hypoglycaemia, diabetes mellitus, fertility problems, myxedema coma, adrenal cortical insufficiency (especially without treatment of the coexisting adrenal insufficiency).
In elderly patients Levothyroxine can lead to increased risk of the coronary artery disease.
Laboratory test’s changes
If patients who treated with Levothyroxine have symptoms of the hyperthyroidism, in their blood can be revealed high level of the fT4 (free tetraiodothyronine) and low level of the TSH (thyroid-stimulating hormone).
In results of the biochemical investigation can be found elevations in liver function tests.
Also can be found signs of the osteopenia.
Side effects in pregnant women
During pregnancy women (especially with known hypothyroidism) should closely monitor their levels of the thyroid hormones, because it’s low level can burden pregnancy course and have negative influence on the baby.
In adequate doses Levothyroxine don’t affect fetus.
But if you have become pregnant during Levothyroxine intake you should contact with your doctor to adjust dose (usually to increase it).
Side effects in children
In infants overdosing can result in craniosynostosis and premature closure of the epiphyses (it can lead to decreasing of the future height in adult person)
In children who receive Levothyroxine for hypothyroidism replacement were reported cases of pseudotumor cerebri and slipped capital femoral epiphyses.
Conclusions
You may never experience any of listed above side effects. And your doctor cannot predict reaction of your body to Levothyroxine until you will try it. That’s why don’t forget to let your physician know if something in your health condition alert you. So when it seems that anything going wrong ask your doctor for advice and he or she will diagnose if your problem is connected with medicine intake. And be careful because some of Levothyroxine side effects require urgent medical help.