Reviewing Thyroid: Take Care of Your Butterfly Gland
Despite the prevalent and increasing statistics of the disorders related to it- why it still top the chart of the diseases about which we are (almost) unaware? How far the medical field has grown to tackle the problems related to it? Lets review it here..
What is Thyroid?
Thyroid is a butterfly shaped, one of the largest endocrine glands of the body located in the base of the neck. Thyroid glands produce, store and release hormones into the bloodstream. It produces two main hormones- triiodothyronine (T3) and thyroxine (T4). These hormones are important for metabolism, brain development, heart and nervous system functions, breathing, cholesterol level and also the regulation of various other functions of different systems of the body.
The proper balance of these two hormones is very essential for the body. Their imbalances bring many disorders which are altogether termed as thyroid disorders. The release of the hormones is regulated by two parts of the brain, hypothalamus and pituitary gland. The hypothalamus releases thyrotropin-releasing hormone (TRH) which orders pituitary gland to tell the thyroid gland the amount of hormones to be released.
Thyroid Disorders: An Unnoticed Epidemic
Amidst the growing concern and awareness related to the diseases like cholesterol, heart problems, depression, diabetes which nowadays increasing due to the lifestyle of the people in the society, thyroid disorders never received similar attention. With time, various forms of thyroid diseases have struck wide range of population. According to the American Cancer Society about 62,450 new cases of thyroid cancer will hit U.S. in 2016 and about 1,980 deaths will occur due to it.
Thyroid diseases have now become very common in India. According to a survey conducted by Indian Thyroid Society, one out of ten adults in India suffers from hypothyroidism. The survey says the women are three times more likely to get hypothyroidism than men.
According to American Thyroid Association (ATA) more than 12% of US population will develop a thyroid condition during their lifetime. About 20 million Americans are currently suffering from some form of thyroid disease.
The manifestation of thyroid disorders is determined by dietary iodine availability. In spite of lack of deep understanding regarding the development of the disease, epidemiology of non-malignant thyroid disease have been well differentiated.
Goiters– It is caused due to abnormal enlargement of the thyroid gland because of its malfunctioning. It occurs mostly due to iodine deficiency. It is endemic in those areas where daily iodine intake is less than 50µg and when the intake falls below 25 µg congenital hypothyroidism can be seen.
In case of congenital hypothyroidism, babies are born with partially developed or improperly functioning thyroid. If it remains untreated it will lead to mental retardation or growth failure.
Hypothyroidism (underactive thyroid)- It is caused due to inadequate production of thyroid hormone by thyroid gland. One of the common causes of hypothyroidism is Hashimoto’s Thyroiditis or Thyroiditis or chronic lymphocytic thyroiditis.
Thyroiditis is an autoimmune disorder which causes chronic inflammation in the thyroid gland. The thyroid cells are damaged by various cells and antibody mediated immune processes. More than 1 million cases of thyroiditis occur every year in India. Other causes of hypothyroidism can be radioactive iodine treatment, previous thyroid surgery, hypothalamus injury.
Some drugs given for various other diseases like interferon alpha given in cancer, amiodarone which is a heart medication, interleukin-2 given in kidney cancer can also cause hypothyroidism by interfering with the thyroid hormone production.
Hyperthyroidism (overactive thyroid)- It is caused due to overproduction of thyroid hormone by thyroid gland. The most common cause of hyperthyroidism is Grave’s disease. Grave’s disease also known as Basedow’s disease is an autoimmune disorder.
Malfunctioning in the immune system releases abnormal antibodies that mimic thyroid stimulating hormone (TSH) giving false signals to thyroid gland to produce thyroid hormones leading to its overproduction ultimately, leading to Grave’s disease.
Other causes can be excessive iodine, thyroiditis, benign tumors of thyroid gland and pituitary gland. In India more than 1 million cases of hyperthyroidism arises every year. Hyperthyroidism affects 2-5% women of age group 20 to 40 years. Women are 2 to 10% more likely to develop hypo and hyperthyroidism than men.
Imbalance of T3 and T4 hormones in the body can also form thyroid nodules, which are the lumps that are formed within the normal thyroid gland. More than 95% cases of thyroid nodules are non cancerous proliferations and some are cysts filled with fluid in place of thyroid tissue.
Thyroid cancer is a rare type of cancer causes when abnormal cells start growing in the thyroid gland. It’s common symptom is the formation of lump in the neck. The reason behind its development is not known. It is generally speculated that too much exposure to the radiation causes thyroid cancer. Thyroid cancer can be detected at early stage and the treatments generally work well.
In Japan, according to recent reports, the Japanese authorities have denied but it has been seen that after the devastation of Fukushima Daiichi nuclear power plant by tsunami in 2011, children residing in Fukushima Prefecture are more prone to suffer from thyroid cancer. Till now more than 160 teenagers have been diagnosed with thyroid cancer residing in the area.
In Western countries, people are likely to have more amount of iodine in the food sources and thus develop a differentiated thyroid cancer called papillary thyroid carcinoma, this one is less common. The more common and invasive one is follicular thyroid carcinoma, some of these patients fail to respond to radiotherapy after removal of thyroid. For such patients new drug, lenvatinib (lenvima) can be helpful. Both the cancers are derived from follicular epithelial cells in the thyroid.
Therapeutics for Thyroid Disorders
Thyroid hormone replacement drugs given for the treatment of hypothyroidism can be man-made or natural.
Levothyroxine – It is a synthetic T4 or thyroxine hormone. It is an oral, daily hormone replacement, synthetic thyroid hormone for hypothyroidism associated with thyroiditis.
It is also manufactured by Pfizer subsidiary, King Pharmaceuticals under the brand name Levoxyl. Jerome Stevens Pharmaceuticals manufactures it under brand name Unithroid. It is manufactured under the brand name Tirosint by Akrimax Pharmaceuticals.
Liothyronine– It is a synthetic T3 or Triiodothyronine hormone. It is used for the treatment of hypothyroidism and a state of decompensated hypothyroidism called Myxedema coma. It is manufactured by the Pfizer subsidiary, King Pharmaceuticals under the brand name Cytomel.
A new time-released synthetic T3 drug, Thyromax is currently in clinical trials for its approval, sponsored by Ipe, LLC.
Liotrix– It is a combination of Synthetic T3/T4 hormone. Liotrix is a 4:1 mixture of synthetic thyroxine and triiodothyronine used for treatment of thyroid deficiency and hypothyroidism. The only brand of liotrix is Thyrolar manufactured by Forest Labs (now acquired by Actavis).
The used of T4/T3 combination drug for the treatment of hypothyroidism is controversial and is currently under research and discussion. The standard treatment given is levothyroxine alone.
The natural animal derived thyroid drugs are known as Natural Desiccated thyroid (NDT). NDT are made of dried thyroid glands of pigs also called “porcine thyroid”, “pig thyroid” or “natural thyroid”.
NDT was the only available thyroid drugs in early 1900s under the brand name, Armour Thyroid which is now manufactured under Actavis/Allergan. Later the synthetic hormone levothyroxine was introduced in 1950s. NDT is also manufactured by RLC Laboratories under the brand name Nature-Throid and WP Thyroid.
For Hyperthyroidism treatment, several antithyroid drugs are used.
Methimazole – It inhibits the use of iodine by thyroid for the production of thyroid hormone.
It is manufactured by King Pharmaceuticals, under the brand name Tapazole.
In UK and Europe, Carbimazole, under the brand name NeoMercazole is used as a pro-drug which metabolizes methimazole.
Propylthiouracil (PTU) is also used for the treatment of hyperthyroidism. It is available only in generic version.
Recombinant TSH drug,Thyrogen is thyrotropin alfa injected to thyroid cancer patients for accurate scanning of thyroid cancer and to avoid the side effects of hypothyroidism. It is manufactured by Genzyme Therapeutics. Thyrogen is a protein prepared to be identical to TSH.
San Francisco based molecular diagnostics company, Veracyte uses Veracyte’s Afirma® Gene Expression Classifier (GEC) for the identification of those patients whose thyroid nodules are benign so that unnecessary surgery can avoided. The company targets to make a ‘liquid biopsy’ blood test for thyroid and lung cancer screening prior to the occurrence of their symptoms.
According to a study done on nearly 8,500 people, “Having too little thyroid hormone in the blood — even in the low-normal range– raises the risk of developing type 2 diabetes”. The results were announced in the Endocrine Society‘s 98th annual meeting occurred last month in Boston.
According to ATA, about 60% of people affected by thyroid diseases are unaware about their condition. This is the situation which needs serious concern. Undiagnosed and inadequately treated hypothyroidism in pregnant women increases the risk of miscarriage, preterm delivery and various developmental disorders in their children. Early diagnosis and detection of thyroid related disorders are very helpful for the patient to lead a better quality of life.
“It is clearly important that we do more to increase awareness of thyroid diseases and cancers, both in the US and globally,” said ATA President Dr. Robert Smallridge.
Note: Veracyte will announce the new data related to the role of gene alterations and transcriptions in thyroid cancer diagnosis at the American Association of Clinical Endocrinologists (AACE) 25th Annual Scientific & Clinical Congress in Orlando, USA starting from today and will end on May 29, 2016.
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Figures legends and credit (from top to bottom in chronology):
Figure 1. Hormones produced by thyroid gland. (Credit: thyroid hormones. © designua, Stock Photo ID: 100655612)
Figure 2. Thyrotropin-releasing hormone (TRH) controls the release of thyroid hormones via pituitary gland.
Figure 3. Thyroid disorders occurrences in Indian men and women (Source: SRL Diagnostics).
Figure 4. Type of Thyroid disorders
Figure 5. Hashimoto’s Thyroiditis (Source: Mayo Clinic, USA)
Figure 6. Graves’ disease (Source: Mayo Clinic, USA)
Figure 7. Thyroid disorders symptoms (Credit: Thyroid issues butterfly shaped word cloud © arloo, Stock Photo ID: 86458025)
Featured image credit: Graphics remixed by Medgenera. World Thyroid Day poster © naumas (Stock Photo ID: 129886406) & Thyroid gland and trachea shwn on a woman silhouette. © naumas (Stock Photo ID: 129886094)