From the Guidelines
Levothyroxine is a synthetic preparation of a natural hormone found in the body that treats hypothyroidism by replacing or supplementing the thyroid hormone thyroxine (T4) in people whose thyroid glands don't produce enough naturally. It is essential for regulating metabolism, energy production, body temperature, heart rate, and brain development 1. The medication is typically taken once daily on an empty stomach, 30-60 minutes before breakfast, to ensure proper absorption. Some key points to consider when prescribing levothyroxine include:
- Dosing is highly individualized, usually starting at a lower dose (25-50 mcg for adults) and gradually increasing based on blood test results measuring thyroid-stimulating hormone (TSH) levels 1.
- Patients should avoid taking levothyroxine with calcium supplements, iron, antacids, or certain foods that can interfere with absorption.
- Full therapeutic effects may take several weeks to develop, and most patients need to continue treatment lifelong with regular monitoring of thyroid function to ensure proper dosing. It is crucial to monitor patients for potential adverse effects, such as those on bone mineral density and the cardiovascular system, including angina, arrhythmia, and increased cardiac wall thickness, as well as the risk of osteoporosis, fractures, abnormal cardiac output, or ventricular hypertrophy due to long-term overdosing 1.
From the FDA Drug Label
Levothyroxine sodium tablets, USP is L-thyroxine (T4) and contains synthetic crystalline L-3’,5’-tetraiodothyronine sodium salt. Synthetic T4 is chemically identical to that produced in the human thyroid gland. Thyroid hormones exert their physiologic actions through control of DNA transcription and protein synthesis. Oral levothyroxine sodium is a synthetic T4 hormone that exerts the same physiologic effect as endogenous T4, thereby maintaining normal T4 levels when a deficiency is present. Levothyroxine sodium tablets are a L-thyroxine (T4) indicated in adult and pediatric patients, including neonates, for: * Hypothyroidism: As replacement therapy in primary (thyroidal), secondary (pituitary), and tertiary (hypothalamic) congenital or acquired hypothyroidism. * Pituitary Thyrotropin (Thyroid‑Stimulating Hormone, TSH) Suppression: As an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer.
Levothyroxine is a synthetic form of the thyroid hormone thyroxine (T4). It works by replacing the missing thyroid hormone in the body, thereby maintaining normal T4 levels when a deficiency is present. Levothyroxine is used to treat hypothyroidism and as an adjunct to surgery and radioiodine therapy in the management of thyrotropin-dependent well-differentiated thyroid cancer 2 2.
From the Research
What is Levothyroxine
- Levothyroxine is a medication used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormones 3, 4, 5, 6, 7.
- It is a synthetic form of thyroxine (T4), a hormone that is naturally produced by the thyroid gland 3, 5.
- Levothyroxine works by replacing the missing thyroid hormones in the body, helping to regulate metabolism, energy production, and overall health 3, 4, 5, 6, 7.
Uses of Levothyroxine
- Levothyroxine is used to treat primary hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormones 3, 4, 5, 6.
- It is also used to treat secondary hypothyroidism, a condition where the pituitary gland does not produce enough thyroid-stimulating hormone (TSH) 5.
- Levothyroxine may be used to suppress TSH levels in patients with thyroid cancer 5.
- It may also be used to treat subclinical hypothyroidism, a condition where TSH levels are elevated but thyroid hormone levels are normal 7.
Effects of Levothyroxine
- Levothyroxine can improve symptoms of hypothyroidism, such as fatigue, weight gain, and dry skin 3, 4, 6.
- It can also improve quality of life and patient satisfaction in patients with hypothyroidism 6.
- However, some patients may not experience significant improvements in symptoms or quality of life with levothyroxine monotherapy, and may require combination therapy with liothyronine (T3) 3, 4, 6.
- Levothyroxine may have beneficial effects on cardiovascular disease risk factors, such as hypertension and dyslipidemia, but its use in subclinical hypothyroidism to reduce cardiovascular disease risk is not clearly beneficial 7.