Thyroid hormones are naturally synthesized in our body, but since the molecules are not complex, many pharmaceutical companies make the synthetic variety of the hormones. There are two basic types of thyroid hormones- T4 known as levothyroxine and T3 known as liothyronine. Both are manufactured and stored in the thyroid gland.
Thyroid hormone from the pharmaceutical companies are obtained in 2 ways.- either derived from animal thyroid gland (bovine or ovine sources) or made synthetic. In the USA, the content and quantity of iodine in the thyroid preparation is well regulated.
Cytomel (liothyronine sodium) is available both as a tablet or the salt of a naturally occuring thyroid hormone. T3 is many times more potent that T4
How thyroid hormones actually work is not really known but their actions involve myriad biochemical changes in the cells. The thyroid hormones generally provide energy to the individual. They increase the consumption of body carbohydrates, lipids and proteins, plus they enhance oxygen consumption. Individuals who take thyroid hormone generally have a higher basal metabolic rate. The thyroid hormones affect almost every organ in the body including the brain. One can only appreciate the importance of thyroid hormone when one observes patients who are deficient in the hormone.
Thyroid hormone is easily absorbed from the stomach into the blood stream. The onset of action is quite rapid and usually occurs in a few hours. The peak activity of the hormone, however, may take several days. The thyroid hormone usually stays in the body for a few days after a single administration. One of the reasons why the thyroid hormone stays in the body for a few days is that in the blood it binds to albumin and is protected from breakdown by the liver.
Indications for thyroid hormone
as a replacement therapy in patients who have hypothyroidism
as a replacement therapy in patients who have had their thyroid removed during surgery
in patients with with goiters and thyroid nodules
as diagnostic agents in suppression tests to differentiate suspected hyperthyroidism from thyroid gland autonomy.
In those patients who have allergies to either pork or beef thyroid, Cytomel (liothyronine sodium) tablets can be used instead.
Body Builders and Weight Loss
For decades, both amateur and professional athletes have abused thyroid hormone to lose weight. Since the thyroid hormone can cause combustion of fats and carbohydrates, many individuals have utlised this ability to lose weight and to perform better at sports. Cytomel has been used by individuals in every type of sport. The thyroid hormone is taken orally for 4-6 weeks and then stopped just a week prior to the event. There is no doubt that Cytomel is a very effective fat burner and enhances exercise performance. Many athletes report that short duration usage of Cytomel can result in loss of weight and increased energy.
While this may be true, the issue becomes very complex because most of these athletes also take a wide variety of other supplements and hormones to lose weight
The people who sell Cytomel over the internet suggest that anyone interested in losing weight should start the drug at 25 ug/day for a few weeks. The dose should only be increased by 5-10ug/day over a few weeks. The maximum dose of Cytomel which can be taken without causing side effects is about 100ug/day. Anecdotal data from athletes indicate that it takes anywhere from 6-12 weeks to lose weight with Cytomel. The crucial thing for all users of Cytomel is to understand that when the drug is stopped, most people will have developed a state of thyroid insufficiency because the Cytomel has suppressed the thyroid gland from making the natural hormone.
So the dose of thyroid hormone should be slowly tapered over a few weeks to months to allow for the thyroid gland to begin working again.
It is highly recommended that all individuals who plan to use thyroid hormone for off-label disorders like weight loss consult with a physician to ensure it is safe.
Signs and Symptoms
Excess thyroid hormone can cause a wide range of side effects ranging from:
Mood alterations- irritability, nervousness, anxiety
Abnormal heart rhythms
Worsening of heart failure
Massive overdosage may result in symptoms resembling thyroid storm. Chronic excessive dosage will produce the signs and symptoms of hyperthyroidism.
Thyroid hormone is generally contraindicated in individuals who have untreated adrenal cortical insufficiency, untreated thyrotoxicosis or have apparent hypersensitivity to any of their active or extraneous constituents. So far, it is believed that true allergic or hypersensitive reactions to liothyronine is very rare.
Signs and Symptoms
Many individuals take thyroid hormone to lose weight. Often the thyroid hormone is combined with other supplements or medicines. In normal patients, the therapeutic doses of thyroid hormone are generally ineffective as weight loss agents. Much larger doses are required to produce weight loss. However, large doses of the thyroid hormones can be quite dangerous and cause life threatening symptoms. These symptoms can be aggravated in the presence of other agents like ephedrine or growth hormone which are also used as weight loss supplements.
There are a few medical conditions where the use of thyroid hormone should be used with caution. Thyroid hormone can aggarvate adrenal cortical insufficiency and both diabetes mellitus and insipidus. The dosage of the thyroid hormone has to be adjusted in such scenarios. Thyroid hormone also increases the sensitivity of the body to oral anti coagulants and can increase the risk of generalized bleeding.
Thyroid hormone is also recommended by non medical professionals in the treatment of infertility. There is zero scientific evidence that thyroid hormone can do anything for infertility.
Thyroid hormones are not harmless and can cause significant side effects. Individuals who have a bad heart or those who get chest pains, should first see a physician before starting thyroid hormone therapy. In all such cases, only the lowest dose of thyroid hormone should be used.
Levels of thyroid hormone can be easily checked. All sporting agencies including the IOC and WADA routinely check all athletes for the presence of thyroid hormones. The available radioimmuno assays are very sensitive and can identify minute anounts of the hormone in the urine.
Liothyronine can interact with a number of drugs including:
Insulin or Oral Hypoglycemics
Estrogen, Oral Contraceptives
In each of the above cases, the physician has the responsibility of making sure that the dosage of thyroid hormone is not excessive. All patients taking thyroid hormone should also be regularly followed by a physician.
Treatment of Overdosage
When thyroid hormone overdosage is suspected, the patient should be admitted to a hospital. The hormone should be temporarily stopped, the patient observed and monitored. Most people who have had an overdose need to stop the hormone for at least 4-8 weeks, to allow the thyroid gland to recover. There are no specific antidotes to treat thyroid overdose- simply supportive care. Vomiting should never be induced for the fear of aspiration into the lungs. If the individual is in a coma, then he/she may require temporary mechanical ventilation in the ICU. In most cases, fluid resuscitation, oxygen and observation will suffice. In a few cases, one may have to administer beta adrenergic blockers to decrease the sympathetic drive.
Liothyronine is available as a tablet which is taken once a day. The dosage of liothyronine depends on the degree of hypothyroidism. Liothyronine sodium therapy should always be started at the lowest dose possible- in view of its relatively rapid onset of action. The starting dosage of Cytomel (liothyronine sodium) tablets is 5 mcg/day, and should be increased by no more than 5 mcg/day increments at 2-3week intervals. Starting a high dose or suddenly increasing the dose can aggravate any preexisting heart condition. In the majority of cases a dose between 50-75 ug/day will suffice. Liothyronine is also available as an intravenous formulation and sometimes used to treat myxedema coma. Myxedema coma is considered a life-threatening complication of hypothyroidism and represents the far more serious side of the spectrum of thyroid disease. This condition is mostly seen in elderly patients and tends to occur more often in women.
Liothyronine is available as 5, 25 and 50 ug tablets. In the USA, a doctor’s prescription is required for l-thyronine.
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