Thyroxine is primarily used for the treatment of hypothyroidism (deficiency of thyroid hormone) and myxedema coma (severe hypothyroidism). It is also used to treat goitre (an enlarged thyroid gland) and congenital hypothyroidism (cretinism).
Levothyroxine is a synthetic form of thyroxine (an internal hormone secreted by the thyroid glands). It works by replacing or providing more thyroid hormone, which is generally produced by the thyroid gland.
Nausea, vomiting, abdominal cramps, palpitations, alteration in menstrual cycle, nervousness and irritability, anxiety, mood changes, headache, diarrhea, insomnia, increased appetite, irregular heartbeat, temporary hair loss, fever, chest pain and discomfort, muscle weakness and flushing.