The thyroid is the small butterfly-shaped endocrine gland situated in the anterior part of the neck bounding the windpipe from the three sides. It secretes hormones that help to regulate different body process, metabolism and growth including the heart rate and rate of producing body calories. Thyroiditis is the medical term for defining the swelling or inflammation of the thyroid gland, which can result in an abnormal increase or decrease in the levels of thyroid hormones in the blood.
Thyroiditis sometimes may make the thyroid gland tender and painful if it is caused due to infection, trauma, or, radiation, or may be absolutely painless if it causes because of autoimmune disorders, an idiopathic fibrotic process or induced by medications. The most common forms are Hashimoto's disease, postpartum thyroiditis, drug-induced thyroiditis, sub-acute granulomatous thyroiditis, infectious thyroiditis, sub-acute lymphocytic thyroiditis, silent or painless thyroiditis, and radiation-induced thyroiditis.
Drug-Induced Thyroiditis: An Overview
The term "drug-induced" refers to mean "caused by or because of any medicine". There are various medicines including molecular-targeted agents, cytokines, amiodarone, α-interferon, iodine, lithium, anti-thyroid drugs, a class of anti-cancer drug containing Sunitinib and others that trigger thyroid dysfunction or drug-induced thyroiditis or thyrotoxicosis by inhibiting thyroid hormone secretion and damaging the thyroid glands. In drug-induced thyroiditis, thyroid gland becomes underactive mainly because of different reactions from certain medications which usually alter the binding of thyroid hormone to globulin protein or the thyroid hormone metabolism and absorption.
Drug-induced thyroiditis can sometimes result in mild to severe pain in the area near the thyroid gland which is generally short-lived and vanishes off once you stop taking the medication responsible for the condition.
Symptoms of Drug-Induced Thyroiditis
- Breakable fingernails
- Nervousness or restlessness
- Coarsening and thinning of hair
- Goiter or feeling like the presence of any lump on your neck
- Cold intolerance
- Tremors with a rapid or slow heartbeat
- Feeling of fuzzy headed
- Dry skin
- Problems in critical thinking and judgment
- Feeling hot
- Bulging out of eyes
- Puffy eyes
- Hungry even after you eat
- Weight loss
- Weight gain
- Swelling of the legs
- Decreased hearing ability
- Body aches
- Decreased concentration
- Menstrual disorders
- Drop in body temperature
- Puffy hands, face, and feet
- Irritability, insomnia, and anxiety
- Slowing of speech
- Thickening of the skin
- Dry and flaky skin or hair
- Eyebrows become thin
- Muscle aches and joint stiffness
- Breathing trouble
- Overall weakness in the body.
Prevalence Rate of Drug-Induced Thyroiditis
Studies indicate that the incidence of drug-induced thyroiditis varies with the dietary iodine intake among the population and is more frequent in areas with low iodine intake or in iodine excess regions. Even the risk of this condition is prevalent much highly in elderly persons probably due to the more underlying thyroid abnormality. Drug-induced thyroiditis is basically a mild clinical condition but it can be severe and life-threatening or lethal.
Prognosis of Drug-Induced Thyroiditis
The prognosis for drug-induced thyroiditis may be very poor in spite of having a huge range of anti-thyroid therapy available. The studies revealed that the patients undergoing Amiodarone treatment have higher levels of TSH and T4 hormones with quite lower levels of T3 hormone. Thus the prognosis highlights the more careful monitoring of patients receiving Amiodarone treatment but it has been seen that short-term amiodarone use is generally safe.
Causes of Drug-Induced Thyroiditis
Drug-induced thyroiditis may be caused by the following reasons.
- Drugs used for overactive thyroid, like propylthiouracil (PTU), potassium iodide, radioactive iodine, and methimazole.
- Treatment with iodides or lithium.
- Consumption of huge amount of iodine-containing seaweed.
- Povidone iodine or Betadine.
- Damage of Thyroid Glands:
- A class of anti-cancer drug containing sunitinib.
- Too much iodine intake by the pregnant woman can lead to the development of temporary hypothyroidism or goiter in newborn or fetus.
Risk Factors of Drug-Induced Thyroiditis
The risk factors involved in the occurrence of drug-induced thyroiditis include the following:
- If the patient is female
- Presence of thyroid abnormality
- Presence of Hashimoto's thyroiditis at present
- Presence of auto immune problem in the thyroid gland
- Partial thyroidectomy
- History of thyroid abnormality
- Previous instances of any radioactive iodine administration
- Family history of thyroid disease
- History of postpartum thyroid disorders.
Complications of Drug-Induced Thyroiditis
The complications associated with drug-induced thyroiditis include the:
- Myxedema Coma as a Complication of Drug-Induced Thyroiditis: This is the most severe form of hypothyroidism, although very much rare but can be caused due to any infection, illness, exposure to cold, and/or through reactions of certain medications. The signs and symptoms include:
- Decrease in normal body temperature
- Abnormally slow breathing
- Lower level of blood pressure
- Lower level of blood sugar
- Unresponsiveness to stimulation i.e., decreased or loss of consciousness.
- Other complications related to drug-induced thyroiditis are:
- Heart disease with slow heart rate may result in heart failure.
- Miscarriage during the time of pregnancy
- Pituitary tumors which are an extremely rare condition.
Diagnosis of Drug-Induced Thyroiditis
A thorough physical examination may sometimes show symptoms of an enlarged thyroid gland. Other signs included are:
- Decrease blood pressure
- Decrease in normal temperature
- Slowing of heart rate.
A physician checks all the above parameters. Blood tests are also essential to determine the abnormal thyroid functions. These include:
- Free amount of T4 in the blood
- T3 levels
- Thyroid stimulating hormone or TSH level.
An ultrasound of the thyroid gland by using sound waves reveals the occurrence of thyroiditis. A thyroid scan is also a good option to find out the proper functioning of thyroid gland. In this case, a dye is injected before taking the pictures and very rarely the patients may face an allergic reaction to this injected dye. Fine needle biopsy is another procedure involved in taking a sample of the thyroid gland for testing of any abnormalities.
Other abnormalities that may also provide the evidence of the disease include:
- CBC results showing anemia.
- Rise of cholesterol level.
- Abnormal increase of liver enzymes.
- Abnormal increase in serum prolactin.
- Lower level of blood glucose.
- Lower level of serum sodium.
Treatment & Management of Drug-Induced Thyroiditis
The first line of treatment includes stopping of consumption of the drug resulting in drug-induced thyroiditis. However, it is not advisable to stop the prescribed medications without asking your physician. Some drugs may lead to life-threatening or unpleasant reactions if not replaced or stopped progressively.
A thyroid replacement hormone, Levothyroxine, is the most normally used medicine to treat drug-induced thyroiditis condition. The dose is adjusted from time to time in order to bring down the TSH level to normal. Once the patient has started thyroid replacement therapy, the patient may face the symptoms of hyperthyroidism or elevated thyroid activity which are mentioned in the following points:
- Fast weight loss
- Restlessness or nervousness
- Excessive sweating.
Hyperthyroidism can be managed through following procedures:
- Medications, such as methimazole and propylthiouracil
- Potassium perchlorate
- Iodinated contrast media
- Calcium Channel Blockers or CCBs
Drug-induced thyroiditis even causes pain in the region around the thyroid gland that can be often treated by non-steroidal anti-inflammatory drugs or NSAIDs, even though corticosteroid medication may frequently be needed. Management or treatment primarily involves only symptomatic relief either of pain or tenderness; if it persists, then restoration of euthyroidism is needed.
Prevention of Drug-Induced Thyroiditis
- Correct detection and management of underlying thyroid abnormalities.
- If the patient is facing potential side effects of anti-thyroid medications then shifting to different medicinal agents is recommended.
- Medications that can cause drug-induced thyroiditis should be used with caution. If any patient is consuming this type of medicines, then patients should undergo screening before consuming such medicines or if consumed, then checking of thyroid levels should be done frequently.
- Patients must be instructed about the adverse effects of anti-thyroid medication therapy because the occurrence of thyrotoxicosis is actually sudden and explosive. Patients must also be educated to look for symptoms like a sore throat, fever, oral ulcers, or jaundice and seek medical help promptly.
- Patient should consume enough amount of iodine in order to prevent a low iodine condition.
- Patient should also consume a sufficient amount of selenium.
- Try to avoid medicines that cause thyroid disorders.
- Try to avoid intaking of goitrogens.
When drug-induced thyroiditis or thyroid dysfunction happens, it is always better to stop or discontinue the consumption of the causative drug. However, one needs to discuss with the doctor before stopping any medications to avoid further complications. The drug-induced thyroiditis commonly resolve with discontinuation of the medicine responsible for the cause.