L-thyroxine in hypothyroidism

L-thyroxine (levothyroxine) is used primarily for the treatment of hypothyroidism. In addition, the hormone can also be used for the treatment of a goiter (goiter) and in special cases in hyperthyroidism. Normally thyroxine is well tolerated, so there are no side effects associated with the therapy. Find out in detail here about the effect and dosage of the hormone and find out why thyroxin should not be used for weight loss.

Thyroxine: action in the body

Thyroxine is an endogenous hormone produced in the thyroid gland. Together with triiodothyronine, another thyroid hormone, it is involved in a variety of processes in the body, including metabolism. In hyperthyroidism (hypothyroidism), the body produces too little thyroxine. This can lead to symptoms such as tiredness, listlessness and concentration problems. To treat such symptoms, L-thyroxine is given to the body.

In addition to hypothyroidism, there are other uses of L-thyroxine. The hormone is also administered,

  • if a benign enlargement of the thyroid (goiter) is present.
  • to prevent new goiter formation after successful goiter surgery.
  • if a patient suffers from a malignant thyroid tumor.
  • if normal thyroid function has been restored in patients with hyperthyroidism (the hormone is used together with antithyroid drugs)

Side effects of thyroxine

Thyroxine is generally considered to be well tolerated, therefore rarely occur during use side effects. If 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 arrhythmia, feeling hot and sweating, trembling, inner restlessness and insomnia.

If you experience any side effects while taking thyroxine, you should always contact your doctor. It may be useful to reduce the dose for a few days or to stop taking the tablets altogether. If the side effects have resolved, treatment with a low dose may be resumed.

Important to take

People with hypothyroidism usually need to take a hormone replacement drug throughout their lives. If a benign goiter is treated, the duration of ingestion is usually between six months and two years.

Ideally, you should take the thyroxine tablet in the morning, chewed at least half an hour before breakfast. As a result, the hormone, which is generally poorly absorbable, can be better absorbed into the body. Take the tablet with some water, but not coffee.

Dosage of thyroxine

The exact dosage of thyroxine always depends on the cause of the treatment, for example, if a hypothyroidism is treated or a further goiter is prevented. If a hypothyroidism is treated, the dosage depends on the severity of the disease.

In case of hypothyroidism, a low dose is started, which can then be further increased if necessary. Especially for patients who have severe or long-existing hypothyroidism, a low starting dose is important. But even in older or very slim people and in patients suffering from coronary heart disease, a low starting dose should be chosen.

Often, hypothyroidism starts with a dose of between 25 and 50 micrograms. This can be increased slowly over time to a maximum of 100 to 200 micrograms. In children, the dosage depends not only on the age but also significantly on the weight of the child. In general, you should always follow the instructions of your doctor when dosing thyroxine.

Avoid overdose

If you take an overdose of thyroxine, it may trigger the typical symptoms of hyperthyroidism. These include symptoms such as palpitations and cardiac arrhythmias, flushing sensation and excessive sweating, as well as inner restlessness, tremors and insomnia. If you forget a tablet, you should not make up for the dose. Keep the given intake rhythm instead.

An overdose can be caused not only by the intake of too many tablets, but also by a wrongly adjusted dose. Therefore, you should have your thyroid scores checked regularly by a doctor. In particular, the thyrotropin value is of importance here since the formation of thyroxine is stimulated by thyrotropin. Such examinations are particularly important during the adjustment phase, during pregnancy and when changing the dose.

Interactions with thyroxine

Some medicines inhibit or reduce the intake of L-thyroxine and should therefore not be taken together with the hormone. These agents include, but are not limited to, colestyramine and colestipol. This also applies to stomach acid-binding antacids, calcium carbonate and medications that contain iron. In addition, agents such as glucocorticoids, beta-blockers, iodine-containing contrast agents and propylthiouracil make L-thyroxine in the body less able to be converted into its more active form.

In addition, during the intake of thyroxine, it may also interact with the following drugs:

  • phenytoin
  • salicylates
  • dicumarol
  • furosemide
  • clofibrate
  • sertraline
  • chloroquine
  • proguanil
  • barbiturates
  • amiodarone

Women taking the birth control pill should be aware that this may increase the need for L-thyroxine. The same applies to women who take hormone replacement therapy after menopause.

Influence on other drugs

Thyroxine is not only potentiated or inhibited by other drugs, but can also affect other drugs. This primarily affects coumarin derivatives that inhibit blood clotting. Its effect is enhanced by the thyroid hormone. Exactly the opposite effect of L-thyroxine on drugs that lower blood sugar. These are weakened in their effect.

In addition to drugs, it can also lead to interactions with certain foods. So you should not take the hormones at the same time with a cup of coffee, as this inhibits the absorption into the blood and the hormone concentration in the blood can fall significantly. Likewise, soy products can inhibit the uptake of L-thyroxine from the gut. If you eat soy products more often, you should tell your doctor about it.

Contraindications of thyroxine

L-thyroxine should not be used if hypersensitivity to the active substance is present. Similarly, the hormone must not be taken by patients with untreated hyperthyroidism. In addition, the tablets must not be prescribed for the following diseases:

  • Fresh heart attack or acute myocardial or heart wall inflammation
  • Untreated adrenal cortex weakness
  • Untreated weakness of the pituitary gland
  • Autonomy of the thyroid gland
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