Can Levothyroxine Be Used For Weight Loss?

Levothyroxine, or L-thyroxine, is a synthetic form of thyroxine, which is one of the principal hormones produced by your thyroid gland. L-thyroxine is used to treat conditions where your thyroid gland does not produce enough thyroid hormone. Normal thyroid hormone levels are essential for optimal growth, development and metabolic function. If your thyroid hormone levels are too high or too low, serious illness can result.

Thyroxine and Cellular Metabolism

Thyroid hormones, including synthetic forms like L-thyroxine, exert a generally energizing effect on your metabolism. A 2010 report in "Endocrine Reviews" describes the complex interplay between thyroid hormones and your cells. The actions of thyroid hormones are exerted at multiple cellular levels, including the mitochondria, which produce energy within your cells, the nucleus, where your chromosomes reside, within the cellular cytoplasm, where most of the cell's metabolism takes place, and at the cell membrane. This multilevel interaction attests to the importance of thyroid hormones in cellular function.

Too Little Thyroxine

If your thyroid gland produces too little thyroxine, a condition called hypothyroidism, your metabolism slows. "The Merck Manual of Diagnosis and Therapy" cites weight gain, cold intolerance, poor mental function, hair loss, personality changes and slowed speech as common symptoms of hypothyroidism. Prolonged or severe hypothyroidism can lead to hypothermia, heart failure, psychosis and even death.

Too Much Thyroxine

If your thyroid gland produces excess amounts of thyroxine, which can result from immune diseases, pituitary problems, or thyroid nodules or tumors, your metabolic rate increases dramatically. Weight loss, rapid heart rate, heart rhythm disturbances, tremor, nervousness, heat intolerance, insomnia, weakness and frequent bowel movements are some of the symptoms of thyroid hormone excess, otherwise known as hyperthyroidism. In women, menstrual abnormalities are also common with hyperthyroidism. When severe, hyperthyroidism can culminate in fever, weakness, muscle wasting, confusion, psychosis, vomiting, diarrhea, coma, shock and death.

Levothyroxine for Weight Loss

If you already have normal thyroid function, taking levothyroxine induces an artificial state of hyperthyroidism. According to PubMed Health, "thyroid hormone should not be used to treat obesity in patients with normal thyroid function. Levothyroxine is ineffective for weight reduction in normal thyroid patients and may cause serious or life-threatening toxicity." If you are trying to lose weight and you do not have hypothyroidism, taking levothyroxine could cause dangerous side effects. Talk with your doctor about safer alternatives.