T3 (Liothyronine sodium or triiodothyronine) is a hormone of the thyroid gland, which is responsible for the growth and development of the body. In Singapore, T3-containing medications are listed in the Third Schedule and are dispensed from pharmacies only on prescription.
T3 is formed from another thyroid hormone thyroxine (T4). Both hormones are secreted and synthesized by thyroid cells in a ratio of 1 to 4 (20% of the hormone triiodothyronine and about 80% of the hormone of thyroxin). Thus, triiodothyronine is produced less.
Unlike other body hormones, the thyroid hormone T3 is characterized by a very wide spectrum of action. It controls almost all organs and tissues, all metabolic processes, oxygen consumption and total energy consumption.
Decreased biosynthesis and secretion of T3 leads to rapid fatigue, drowsiness and development of metabolic disorders, and hypothyroidism. Treatment of pathological conditions caused by the hormone deficiency can be carried out with the help of hormone replacement therapy.
Drugs of choice in the treatment of hypothyroidism are synthetic analogues of the thyroid hormone T3. In retail and online pharmacies of Singapore, T3 is available under the trade names:
• Cytomel.
• Triostat.
• Tertroxin.
• Liothyronine sodium.
The action mechanism of the drugs that contain a synthetic analogue of the hormone T3 is fully known. However, it was discovered that by the feedback mechanism, the drugs impact the hypothalamus, anterior pituitary and thyroid.
Due to this, the concentration of the circulating T3 hormone in the blood is regulated. Children need this hormone for the growth and development of the central nervous system.
T3 (Liothyronine sodium) is recommended for use in the following diseases or conditions:
• Cretinism.
• Hypothyroidism.
• Coma of myxedema.
• Simple (non- toxic) goiter.
The thyroid hormone T3 is supplied to the pharmaceutical market of Singapore in the form of:
• Oral tablets.
• Powder for solution for injection.
Dosage of the synthetic T3 (Liothyronine) is selected individually for each patient, based on the clinical manifestations of the disease and age.
The starting dose of T3 for the treatment of hypothyroidism in adults is 25 mcg per day. If necessary, the daily dose is increased by 12.5 mcg or 25 mcg every two weeks. The support dose varies from 25 mcg to 75 mcg per day.
For some patients, low doses of T3 may be quite effective, while other patients may require higher doses (up to 100 mcg).
The recommended daily intake for children and the elderly is 5 mcg. Tablets can be ground into a powder and mixed with lactose.
The initial dose of T3 for treatment of goiter is 5 mcg per day during the first week. The daily dose is divided into several doses and increased every seven days by 5mcg to 10 mcg. The recommended daily dose of the thyroid hormone is 75 mcg.
As a rule, myxedematous patients are very sensitive to T3, so treatment starts with low doses, which are gradually increased. The recommended initial dose of triiodothyronine is 5 mcg. Every one or two weeks, the daily dose is gradually increased to 50 -100 mcg.
However, the treatment of myxedema coma is recommended to begin with intravenous administration of T3, followed by a switch to oral forms of the drug. Singaporeans can buy T3 in the form of a solution for injection on prescription at any local pharmacy.
The drug is supplied in glass ampoules. Each ampoule contains 20mcg of T3. The contents of one ampoule are diluted in 1-2 ml in water for injection.
Typically, the injection form of T3 (Liothyronine) is administered intravenously. The intramuscular route of administration of the solution can cause swelling and irritation of the soft tissues. The recommended dose can be 5 mcg to 20 mcg every 12 hours.
Contraindications to the use of T3 are individual sensitivity to the components of the drug, as well as the presence in the patient of such diseases as thyrotoxicosis, and cardiovascular diseases, including angina.
The combination of synthetic T3 with certain drugs can reduce the effectiveness of hormone replacement therapy and cause side effects.
T3 in combination with hypoglycemic drugs can reduce their therapeutic effect. Therefore, when patients with diabetes mellitus are prescribed triiodothyronine, they need to monitor their blood sugar levels.
It should be noted that synthetic T3 enhances the pharmacological effect of antidepressants and anticoagulants. Oral contraceptives reduce the effect of the thyroid hormone.
When the recommended dosages are observed, side effects are rarely observed. However, some patients in the early days of T3 treatment may experience:
• Tremor.
• Nervousness.
• Headache.
• Cardiopalmus.
• Violations of the menstrual cycle.
Each patient has a different response to T3. T3 tablets sometimes reduce appetite, and patients lose weight, while in others, the hormone promotes weight gain. However, an unquestionable argument in favor of T3 is its good safety profile and high efficiency.
As of today, T3 is the most well studied way to treat hypothyroidism. In Singapore, T3 can be purchased not only in retail pharmacy chains, but also ordered in an online pharmacy.
When a patient buys T3 online, he gets the opportunity to quickly start treatment for hypothyroidism and avoid complications.
However, patients should consult a specialist, who will decide upon the need and form of therapy, before they start using triiodothyronine.