Antithyroid drugs

Thionamides propylthiouracil and methimazole.

Concentrated by the thyroid gland and inhibit thyroid hormone synthesis by interfering with thyroid peroxidase mediated iodination of tyrosine residues in thyroglobulin, an important step in synthesis of thyroxine and triiodothyronine.

Can block the conversion of thyroxine to triiodothyronine within the thyroid and in peripheral tissues.

These agents decrease thyroid hormone synthesis, and secretion, and can restore euthyroidism in patients with hyperthyroidism.

Have important immunosuppressive effects resulting in a decrease of serum concentrations of antithyrotropin-receptor antibodies.

May induce apoptosis of intrathyroidal lymphocytes, decrease HLA class II expression, increase number of circulating suppressor T cells, decrease the number of helper T cells, natural killer cells, and activated intrathyroidal T cells.

The primary goals of treatment are to eliminate excess thyroid hormone and minimize the long-term consequences of the disease.

Treatments include radioactive iodine, antithyroid medications with propylthiouracil, methimazole, and surgery.

Beta-blockers may be used to provide symptomatic relief.

Antibodies, called thyroid-stimulating immunoglobulins (TSIs), cause the thyroid to grow and make excess thyroid hormone

TSIs bind to thyroid cell receptors, and cause the thyroid to produce too much thyroid hormone, leading to hyperthyroidism.

In Graves’ disease, B- and T-lymphocyte–mediated autoimmunity is directed at familiar thyroid antigens—thyroglobulin, thyroid peroxidase, sodium-iodide symporter, and the thyrotropin receptor.

The thyrotropin receptor is the primary autoantigen of Graves’ disease and is responsible for the manifestation of hyperthyroidism.

Uncommon manifestations of Graves’ disease include Graves’ dermopathy, with reddening and thickening of the skin, often on the shins or tops of the feet and Graves’ ophthalmopathy

Complications associated with Graves’ disease, including pregnancy issues, heart disorders, osteoporosis, and thyroid storm.

Possible complications during pregnancy include miscarriage, preterm birth, fetal thyroid dysfunction, poor fetal growth, maternal heart failure, and preeclampsia.

Graves’ disease can lead to heart rhythm disorders, changes in the structure and function of heart muscles, and heart failure.

Untreated hyperthyroidism also can lead to weak, brittle bones.

Thyroid storm is a rare, life-threatening complication also known as accelerated hyperthyroidism or thyrotoxic crisis.

Thyrotoxic crisis is more likely when severe hyperthyroidism is untreated or treated inadequately.

Serious adverse effects include fever, profuse sweating, vomiting, diarrhea, delirium, severe weakness, seizures, markedly irregular heartbeat, jaundice, hypotension, and coma.

Thyroid storm often requires immediate emergency care.

TSH and thyroid levels are usually elevated in Graves’ disease.

The primary goals of treatment for hyperthyroidism are to eliminate excess thyroid hormone and minimize the long-term consequences.

Treatments include radio-active iodine, antithyroid medications such as propylthiouracil, methimazole and surgery.

Beta-blockers are sometimes added to provide symptomatic relief.

The usual dose for radioactive Iodine therapy ranges from 5 to 15 mCi of 131.

In general, higher dosages are required for patients who have large goiters or low radioiodine uptake, or who have been pretreated with antithyroid drugs.

The radioiodine goes into the thyroid cells and, over time, overactive thyroid cells are destroyed, thyroid gland shrinks, and in several weeks to months, hyperthyroid symptoms gradually diminish.

Radioactive iodine treatment cures hyperthyroidism in more than 90% of patients with Graves’ disease or autonomous thyroid nodules.

Radioactive iodine therapy may temporarily increase the risk of symptoms of Graves’ ophthalmopathy.

Radioactive iodine therapy side effects include tenderness in the neck and a temporary increase in thyroid hormone levels.

Radioactive iodine therapy is not utilized in pregnant or nursing women.

Patients taking antithyroid drugs must discontinue the medication at least 2 days prior to taking the radiopharmaceutical.

Radioactive iodine causes a hypothyroid state due to the destruction of the thyroid gland, which usually occurs 2 to 3 months after administering the drug.

Antithyroid medications work by blocking the thyroid’s use of iodine to produce hormones.

These medications include oral propylthiouracil and methimazole.

Propylthiouracil may be used when patients cannot tolerate methimazole, radioactive iodine, or surgery.

With propylthiouracil, methimazole a relapse of hyperthyroidism may occur over time.

Anti thyroid medications propylthiouracil, methimazole block the coupling reaction of monoiodotyrosine and diiodotyrosine to produce T4 and T3, thus prevent synthesis of thyroid hormone.

Propylthiouracil, but not MMI, inhibits peripheral conversion of T4 to T3.

Initial propylthiouracil oral doses range between 300 and 600 mg daily.

Initial oral doses of methimazole, which is 10 times more potent than propylthiouracil, range between 30 and 60 mg daily.

Cutaneous reactions are more common with methimazole.




Hepatotoxicity is more common with propylthiouracil.




Long term use of ATDs have been recorded, and use for Graves’ orbital disease.






These medications are traditionally divided into three to four doses daily, they may be administered as single doses.

Clinical improvement is observed at 4 to 8 weeks.

Treatment is continued for 12 to 24 months to achieve lifelong remission.

These drugs may be used before or after radioactive iodine as a supplemental treatment.

Adverse effects of both drugs include rash, joint pain, liver failure, and a decrease in

white blood cells.

Antithyroid medications are not usually used to treat pregnant women in the first trimester.

Propylthiouracil may be considered the pref2242ed drug of choice just before and during the first trimester of pregnancy.

Propylthiouracil can cause potentially fatal or severe liver injury and acute liver failure in adults and pediatric patients.

Antithyroid medications do not inhibit the production of thyroid hormones.

Antithyroid medications block the effect of hormones on the body.

Antithyroid medications may provide relief of irregular heartbeats, tremors, anxiety or irritability, heat intolerance, sweating, diarrhea, and muscle weakness.

Beta-blockers are commonly used.

Surgery to remove all or part of the thyroid gland is an option for the treatment of Graves’ disease.

Topical creams or ointments containing hydro-cortisone may help relieve swelling and reddening of dermopathy.


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