L-thyroxine (levothyroxine) is primarily used to treat hypothyroidism. In addition, however, the hormone can also be used to treat goiter (goiter) and, in special cases, hyperthyroidism. Normally, thyroxine is well tolerated, so that no side effects occur during therapy. Find out here in detail about the effect and dosage of the hormone and learn why thyroxine should not be used for weight loss.
Thyroxine: effect in the body
Thyroxine is a hormone produced in the body by the thyroid gland. Together with triiodothyronine, another thyroid hormone, it is involved in a wide variety of processes in the body, including metabolism.
L-thyroxine for hypothyroidism
In hypothyroidism, the body makes too little thyroxine. This can cause symptoms such as fatigue, listlessness, and difficulty concentrating, among others. To treat such symptoms, the body is supplied with L-thyroxine. In addition to hypothyroidism, however, there are other areas of application for L-thyroxine. Namely, the hormone is also administered,
- When there is a benign enlargement of the thyroid gland (goiter).
- To prevent a new goiter formation after a successful goiter surgery.
- When a patient suffers from a malignant thyroid tumor.
- When normal thyroid function has been restored in patients with hyperthyroidism (here the hormone is used together with thyrostatic drugs).
Side effects of thyroxine
Thyroxine is generally considered to be well tolerated, that is why side effects rarely occur during use. If the amount of the dose is not tolerated or there is an overdose, the typical symptoms of hyperthyroidism may occur. These include signs such as:
- Palpitations and cardiac arrhythmias.
- Feeling of heat and sweating
- Trembling
- Inner restlessness
- Insomnia
If you experience side effects while taking thyroxine, you should always contact your attending physician. It may then be useful to reduce the dose for a few days or stop taking the tablets altogether. Once the side effects have subsided, treatment can be resumed at a lower dose.
Important information about taking the tablets
People with hypothyroidism usually need to take a hormone replacement drug for the rest of their lives. If a benign goiter is treated, the duration of intake is usually between six months and two years. Ideally, you should take the thyroxine tablet in the morning, unchewed, at least half an hour before breakfast. This allows the hormone, which is generally poorly absorbed, to be better absorbed into the body. Take the tablet with some water, but not with coffee.
Dosage of thyroxine
The exact dosage of thyroxine always depends on the cause of the treatment, for example, whether an underactive thyroid is being treated or a new goiter is being prevented. If hypothyroidism is to be treated, the dosage depends on the severity of the disease. In the case of hypothyroidism, a low dose is started first, which can then be further increased as needed. Especially for patients suffering from severe or long-standing hypothyroidism, a low initial dose is important. However, a low initial dose should also be selected for older or very slim individuals, as well as for patients suffering from coronary artery disease. Often, hypothyroidism is started with a dose between 25 and 50 micrograms. This can be further increased slowly over time to a maximum of 100 to 200 micrograms. In children, the dosage depends not only on age but also significantly on the weight of the child. In general, you should always follow your doctor’s instructions when dosing thyroxine.
Avoid overdose
If you have taken an overdose of thyroxine, this can cause the typical symptoms of hyperthyroidism. This is accompanied by signs such as palpitations and cardiac arrhythmias, feeling hot and excessive sweating, as well as inner restlessness, tremors and insomnia, among others.If you miss a tablet, you should not make up the dose because of this. Instead, keep to the prescribed dosing schedule. An overdose can result not only from taking too many tablets, but also from an incorrectly adjusted dose. Therefore, you should have your thyroid values checked regularly by a doctor. Here, the thyrotropin value is of particular importance, since thyrotropin stimulates the formation of thyroxin. Such examinations are especially important during the adjustment phase, during pregnancy, and when the dose is changed.
Interactions with thyroxine
Some medications inhibit or reduce the absorption of L-thyroxine and therefore should not be taken together with the hormone. These agents include colestyramine and colestipol. The same applies to antacids that bind gastric acid, calcium carbonate and drugs containing iron. In addition, agents such as glucocorticoids, beta-blockers, iodine-containing contrast media and propylthiouracil make it more difficult for L-thyroxine to be converted into its more effective form in the body. In addition, interactions may also occur with the following medications while taking thyroxine:
- Phenytoin
- Salicylate
- Dicumarol
- Furosemide
- Clofibrate
- Sertraline
- Chloroquine
- Proguanil
- Barbiturates
- Amiodarone
For women taking birth control pills, it must be taken into account that this may increase the need for L-thyroxine. The same applies to women who take hormone replacement therapy after menopause.
Influence on other medications
Thyroxine is not only enhanced or inhibited in its action by other drugs, but can itself influence other agents. Primarily affected are coumarin derivatives, which inhibit blood clotting. Their effect is enhanced by the thyroid hormone. L-thyroxine has exactly the opposite effect on drugs that lower blood sugar. These are weakened in their effect.
Interactions with food
In addition to medications, there may also be interactions with certain foods. For example, you should not take the hormones at the same time as a cup of coffee, as this inhibits the absorption into the blood and the hormone concentration in the blood can drop significantly. Similarly, soy products can inhibit the absorption of L-thyroxine from the intestine. If you eat soy products more frequently, you should tell your doctor about this.
Contraindications of thyroxine
L-thyroxine must not be used if there is hypersensitivity to the active ingredient. Similarly, the hormone must not be taken by patients with untreated hyperthyroidism. In addition, the tablets must also not be prescribed for the following conditions:
- Fresh myocardial infarction or acute myocarditis or inflammation of the heart wall.
- Untreated adrenocortical insufficiency
- Untreated weakness of the pituitary gland
- Autonomy of the thyroid gland
