Levothyroxine is the generic name for the medication that is often prescribed when a person has low levels of thyroid hormone, or hypothyroidism. It is essentially a synthetic version of the thyroid hormone that is normally produced within the thyroid gland. The medical reference UpToDate reports that there are several brand-name formulations available as well as the generic form: Levothroid, Levoxyl, Synthroid and Unithroid. Any of these formulations may result in gastrointestinal side effects.
Weight Loss
The medical text "Greenspan's Basic and Clinical Endocrinology" indicates that the side effects of levothyroxine therapy may relate to the patient receiving too high a dose; the effects then appear similar to symptoms of hyperthyroidism, in which the patient has abnormally high levels of thyroid hormone. One such potential side effect is that of weight loss, which occurs because the metabolism is "revved up" and results in calories being consumed more rapidly than usual.
Increased Appetite
Another possible digestive system-related side effect is that of increased appetite. As with the side effect of weight loss, this is likely related to an incorrect dosage of levothyroxine--if too much is given the patient will show the same types of symptoms seen in hyperthyroidism; one of these symptoms is a greatly increased appetite. Ironically, despite the increased appetite, weight loss may continue to occur.
Abdominal Cramps, Nausea, Vomiting and Diarrhea
The medical reference UpToDate does not specify what percentage of patients taking levothyroxine experience unpleasant side effects like cramps, nausea and diarrhea; similarly, Medline Plus, a health information website associated with the National Institutes of Health, merely lists these side effects as possible results of taking too much levothyroxine. If patients are experiencing any of these side effects--as well as side effects that are unrelated to the digestive system--it is important that they notify their healthcare providers, as a change in the dose of the medication may be needed.
References
- Levothyroxine
- What medications are approved to treat hypothyroidism?
- "Greenspan's Basic & Clinical Endocrinology;" David G. Gardner and Dolores Shoback; 2007
- "UpToDate"; Denise S. Basow; 2010
