What is Levothyroxine

Levothyroxine which is also known as T4Levothyroxine which is a synthetic isomer of thyroxine, a hormone that is secreted by the thyroid glands. It is indicated for the treatment of primary, secondary and tertiary hypothyroidism. Hypothyroidism is a condition that is caused by insufficient levels of the thyroid hormone in the body because of defective thyroid glands. This can be due to injury, negative effects from other medications or surgical removal. Thyroid hormones are very crucial to the body system since they facilitate numerous physiological activities in the body which will are all essential; their functions revolve around mental health and the development of physical characteristics. Levothyroxine inhibits the secretion of thyrotropin in the management of chronic lymphatic thyroiditis and goiter, and it can also be used in combination with other anti-thyroid agents to prevent the development of goitrogenesis or hypothyroidism in the treatment of thyrotoxicosis. The intravenous form of levothyroxine is indicated for treating stupor and myxedema coma. Levothyroxine has a hormonal content that is uniquely standardized and its effects are more predictable than those of other drugs like thyroglobulin and that is the why it is the preferred method of treatment for hypothyroidism over the other drugs. Levothyroxine provides only T4 for the body but up to 80% of it is broken down into T3 and reverse-T3 which is then utilized by the body. T3 is up to four times more potent, which means that it is stronger and effective than T4. After conversion, it is transported to various parts of the body where it is needed the most. This medication was approved by the FDA in 1950 for clinical use but most physicians had already been using it without approval from the FDA.

Levothyroxine Mechanism of Action

Thyroid hormones enhance the consumption of oxygen by tissues in the body by elevating the body’s metabolic rates. This has profound effects on nearly all organs in the body and it is essential to the normal development of the Central Nervous System. Levothyroxine (T4) has the same mode of action as endogenous thyroid hormone. Liothyronine (T3) is the principal conductor of these activities but Levothyroxine (T4) is the main hormone that is produced by the glands then metabolized into T3. Thyroid hormone influences the growth, development, and maturation of body tissues, it enhances the body’s utilization of energy and it affects the turnover for all substrates in the body. This is made possible by controlling DNA transcription and protein synthesis. This hormone also plays an important role in catabolic and anabolic functions during the development of the Central Nervous System in infants. It regulates cell proliferation, cell differentiation, nerve myelination and the development of axonal and dendritic nerve processes in the nervous system. Thyroid hormone together with somatotropin are responsible for regulating the growth and development of bones and teeth. Thyroid hormone minimizes the accumulation of cholesterol in the liver and the bloodstream and it has a direct cardiostimulatory action. The administration of thyroid hormone to a patient increases cardiac consumption which in turn results in an increased cardiac output and more blood circulation in the body. When exogenous thyroid is given to a patient with hypothyroidism, it increases the patient’s metabolic rates by prioritizing and enhancing the metabolism of proteins and carbohydrates, increasing glucogenesis, mobilizing glycogen stores and enhancing protein synthesis. It also increases the numbers and activity rates of mitochondria in nearly all cells of the body.

The management of hypothyroidism using Levothyroxine or other forms of thyroid hormones eventually improves the body’s cardiac output, heart rates and ventricular contractions in the heart. This facilitates an increase in the rates and depths of breathing, systemic vasodilation, gastrointestinal tract motility and an improved return to consciousness.

How to Use Levothyroxine

Levothyroxine can be administered orally or intravenously. Once in the body, it metabolizes very slowly through sequential deterioration. Both Levothyroxine and Liothyronine are metabolized completely in the liver but they can also be degraded at multiple other sites in the body which include the liver and some parts along the digestive tract.

Oral forms of this medication should be taken once in a day on an empty stomach at around 30 minutes to one hour before your breakfast. It should be taken with a full glass of water unless instructed otherwise by a physician. If you are taking a capsule, swallow it as a whole. You should never crush it, split it or chew it. Infants who cannot swallow the whole capsule can be given a tablet form which can be crushed and mixed in 5-10ml of water. You should always seek medical advice before mixing this medicine and you should never mix it in advance.

This dosage is prepared according to an individual’s age, weight, lab test results, current medical condition and their response to the treatment. It should be used regularly in order to experience the full benefits.

There are many brands of Levothyroxine. You should never change your brand before consulting your doctor. You should also take this medication without skipping doses. Do not stop your administration without the knowledge and permission of your doctor. Always consult your pharmacist for clarification on any information that you might find confusing.


Contraindications and Precautions when using Levothyroxine.

You should never use this medicine if you are hypersensitive to any of its constituents which partially include: gelatin, calcium sulfate, starch, stearic acid, talc, and sucrose.

Certain medications such as Colestipol, antacids, Simethicone, Sucralfate, Sodium Polystyrene Sulfonate, Orlistat and Calcium supplements can interfere with the rates of absorption of thyroid hormones in your body. If you are on medication containing any of these substances, separate your administration periods with Levothyroxine by at least four hours.

Before you start using this medicine, you should inform your doctor of your active medical status and your medical history. Especially if you have had heart diseases, diabetes, high blood pressure, adrenal gland complications and thyrotoxicosis( Increased thyroid hormones).

Before treatment, you should inform your doctor of all the other medications that you are currently on. These should include all the prescription and non-prescription drugs, herbal products, food supplements and illegal drugs because they can have great effects on your response to the medication.

Current studies have shown that Levothyroxine is safe for use during pregnancy but you should communicate to your doctor because your dosage might need to be adjusted. Levothyroxine passes through to breast milk but it has proved to have no effects on a nursing infant.

Side Effects Of Levothyroxine

Levothyroxine is a medication that has minimum side effects but one of its common effects is hair loss during the first few months of administering this treatment. This effect is usually temporary because your body is adjusting to this medication and after a few months, your hair will grow and go back to normal. If this effect persists, you should communicate to your doctor.

When a patient is put on Levothyroxine medication, it is probably because they will gain more benefits than the risks from the side effects. You should, however, inform your doctor of any effects related to high levels of thyroid hormones in the serum which might include; increased sweating, sensitivity to heat, mood changes, tremor and shaking, diarrhea, headaches, shortness of breath, chest pains, irregular heartbeats, dizziness, and seizures.

This list does not include all the side effects. If you experience any other adverse reactions after administering this medication contact your doctor immediately.


If someone overdoses on this drug or has difficulty breathing after its administration contact emergency services immediately. You should never share your medication with others and you must ensure that you have periodic lab tests so that your doctor can monitor your progress and your response to the medication.

If you miss a dose, you should take it as soon as you can.
Store this medication at room temperature, away from direct sunlight and heat. You should always keep all medicine away from your pets and far from the reach of children. If this medication expires or is no longer needed, it should be discarded properly and never flushed in drainage systems like the sink.

For more information on this medication and its administration, feel free to contact us.