Levothyroxine

Levothyroxine is a synthetic form of thyroxine (T4) used to replace or supplement thyroid hormone, chiefly in hypothyroidism. Tissues convert T4 into the more active hormone triiodothyronine (T3).

Thyroxine: Thyroxine, or T4, is a thyroid hormone with four iodine atoms that circulates in blood and can be converted to T3. Levothyroxine is a synthetic version of this hormone.
Hypothyroidism: Hypothyroidism is a condition in which the body has insufficient thyroid hormone activity. Levothyroxine is the standard hormone replacement for most forms.
Thyroid gland: The thyroid gland is an endocrine organ that produces hormones regulating metabolism, growth, and development. Levothyroxine replaces hormone output when this gland cannot meet the body's needs.
Liothyronine: Liothyronine is a synthetic form of triiodothyronine (T3), the more active thyroid hormone. Unlike levothyroxine, it supplies T3 directly and acts more rapidly.
Atrial fibrillation: Atrial fibrillation is an irregular heart rhythm arising in the heart's upper chambers. Excess thyroid hormone from over-replacement can increase the risk of this rhythm disorder.
Triiodothyronine: Triiodothyronine, or T3, is a thyroid hormone that binds thyroid hormone receptors more strongly than T4. Conversion of levothyroxine-derived T4 to T3 supplies much of the active hormone.
Hashimoto's thyroiditis: Hashimoto's thyroiditis is an autoimmune disease in which immune attack gradually damages the thyroid gland. It is a common cause of permanent hypothyroidism requiring replacement.
Oral drug absorption: Oral drug absorption is the movement of a medicine from the digestive tract into the bloodstream. Food and other medicines can reduce or alter levothyroxine absorption.
Desiccated thyroid extract: Desiccated thyroid extract is a medication made from dried animal thyroid glands and containing T4 and T3. It provides a variable mixture of hormones rather than levothyroxine's T4 alone.
Osteoporosis: Osteoporosis is a disease in which reduced bone strength increases fracture risk. Long-term excessive thyroid hormone exposure can accelerate bone loss.

Linked from 10 pages