World Thyroid day
Every year, 25th of May is celebrated as the World Thyroid Day (WTD), marking it as a day to promote awareness and understanding of thyroid health and the advances made in treating thyroid diseases. As of today (25th May, 2015) a PubMed search (a free search engine accessing primarily the MEDLINE database on life sciences and biomedical subjects) retrieves more than 1,76,546 research articles linked to ‘thyroid’, implicating the significance of this research worldwide.
The thyroid gland produces hormones which regulates the body’s metabolism, and affects critical body functions such as energy levels and heart rate. These hormones influence every cell, tissue and organ in the body. About 200 million people worldwide including about 20 million Americans have some form of thyroid disease, and more than 12 percent of the U.S. population will develop a thyroid condition during their lifetime. Perhaps the most stunning statistic is that up to 60 percent of those with thyroid disease are unaware of their condition and that women are five to eight times more likely than men to have thyroid problems.
We at biotechin.asia would like to thank the entire scientific community for their commitment to thyroid research and would like to create awareness about these issues by sharing some information available.
History of Thyroid Research:
The earliest references to thyroid gland was in 1600 BC when the Chinese used burnt sponge and seaweed for the treatment of goiters- which is an enlargement of the thyroid gland. In 15 AD, Celsus first described it as a tumour of the neck (bronchoceole). In 150 AD, Galen, a pioneer in modern medicine suggested the use of burnt sponge for the treatment of goiter and also claimed (incorrectly) that the role of thyroid was to lubricate the larynx.
In 650 AD, Sun Ssu-Mo was the first to use a combination of seaweed and dried powdered mollusc shells and chopped up thyroid gland for the treatment of goitres. Only in 1475, did Wang Hei anatomically describe the thyroid gland and recommended that the treatment of goitres should be dried thyroid. Almost fifty years later, Paracelsus recognized goitres to be mineral impurities in the water. Finally in the year 1656, Thomas Wharton named it thyroid gland, meaning shield due to its shape- since it is resembled the shields commonly used in ancient Greece.
In 1811, Paris discovered iodine in the burnt ashes of seaweed and the idea that this was the active ingredient in the treatments that were prescribed for goiters was developed. Ten years later, Prout was the first to recommend iodine in the treatment of goitres. In the meanwhile, many researchers followed working on goitres and recommended several treatment methods. Ludwig Rehn a German a physician carried out the first thyroidectomy (removal of the thyroid gland) for exophthalmic goitre in 1880.
In the 1880s Theodor Kocher, a famous scientist and a great surgeon performed over 2000 thyroidectomies, and demonstrated that total thyroidectomy caused hypothyroidism. He reported his early experience of thyroidectomy for Grave’s disease, which had a mortality rate of 13% at that time. His recommendation as treatment for total thyroidectomy was a “half a sheep’s thyroid lightly fried and taken with currant jelly once a week“. The modern treatment of hypothyroidism was now born. Kocher was awarded the Nobel Prize for Medicine in 1909.
The idea that the thyroid produces an iodine containing substance was investigated in the last century. In fact, in the year 1914, Edward Calvin Kendall for the first time isolated thyroxine, an active hormone of the thyroid gland. Interestingly, Kendall assigned the incorrect structure to L- thyroxine but his crystalline extract was of the correct structure and biological activity. Kendall erroneously thought that the compound contained an indole nucleus. This discovery by Kendall and his work on the adrenal gland hormones were rewarded the Nobel Prize for medicine in 1950.
Even though thyroxine became available to clinicians in the 1920s, it was expensive, as three tons of animal thyroid only yielded 33g of thyroxine. In 1952, Rosalind Pitt-Rivers and her post doctoral fellow Jack Gross discovered and synthesised tri-iodothyronine showing it was biologically more active than the thyroxine.
What is Thyroid Gland?
The butterfly-shaped Thyroid gland is one of the largest endocrine glands consisting of two lobes connected by an isthmus. It is located in the base of the neck, just below the thyroid cartilage that forms ‘Adam’s apple’. This brownish-red colored gland is rich with blood vessels. It plays a vital role in our body, influencing the function of many of the body’s vital organs including the heart, brain, liver, kidneys and skin. Ensuring a smooth functioning of this gland, is pivotal to a person’s overall well-being.
This gland produces thyroid hormones- principal ones being triiodothyronine (T3) and thyroxine (also referred to as tetraiodothyronine or T4. These hormones regulate the growth and rate of function of many other systems in the body. T3 and T4 are synthesized from iodine and tyrosine. The thyroid also produces calcitonin, which plays a role in calcium homeostasis. The hormonal output from thyroid gland is regulated by the thyroid-stimulating hormone (TSH) produced by the anterior pituitary, which in turn is regulated by the thyrotropin-releasing hormone (TRH) produced by the hypothalamus.
In addition, Thyroid hormone is required for normal brain and somatic tissue development in the fetus and neonates. American Thyoid Association President Dr. Robert Smallridge observes, “The World Health Organization (WHO) has identified iodine deficiency as the world’s most prevalent, yet easily preventable, cause of brain damage. (Iodine is an essential element in normal thyroid function. Since the body doesn’t make it, iodine must be ingested through the diet.) Consequences of iodine deficiency include physical and mental retardation, cretinism, endemic goiter, hypothyroidism, and poor outcomes in pregnancy.” “I am proud to note that this year the ATA, the Endocrine Society, and the American Academy of Pediatrics, in cooperation with the Council for Responsible Nutrition (the trade association for the dietary supplement and functional food industry), released dietary guidelines for supplement manufacturers, stating that pregnant and lactating women should receive a daily multivitamin/mineral supplement that contains 150 mcg of iodine. This level of support is critical to assure normal brain development of the fetus and baby. Setting a standard is an important step in addressing this overwhelming, yet preventable, global health issue,” Dr. Smallridge concludes.
How are Thyroid Hormones synthesized and released?
Synthesis of thyroid hormones requires iodine. Iodine, ingested in food and water as iodide, is actively concentrated by the thyroid and converted to organic iodine within follicular cells by thyroid peroxidase. The follicular cells surround a space filled with colloid, which consists of thyroglobulin, a glycoprotein containing tyrosine within its matrix. All reactions necessary for the formation and release of T3 and T4 are controlled by thyroid-stimulating hormone (TSH), which is secreted by pituitary thyrotropic cells.
TSH secretion is controlled by a negative feedback mechanism in the pituitary gland. Increased levels of free T4 and T3 inhibit TSH synthesis and secretion, whereas decreased levels increase TSH secretion. TSH secretion is also influenced by thyrotropin -releasing hormone (TRH), which is synthesized in the hypothalamus. The precise mechanisms regulating TRH synthesis and release are unclear, although negative feedback from thyroid hormones inhibits TRH synthesis. Most circulating T3 is produced outside the thyroid by monodeiodination of T4 . Only one fifth of circulating T3 is secreted directly by the thyroid.
What are some of the common Thyroid diseases?
As mentioned above, the thyroid plays an important role in regulating numerous metabolic processes throughout the body. An impaired function of thyroid is a medical condition, called thyroid disease. There are several thyroid diseases including Hashimoto’s thyroiditis, hyperthyroidism, hypothyroidism, goiters, thyroid nodules and thyroid cancers. Different types of thyroid disorders affect either its structure or function. Moreover, these diseases have a wide variety of symptoms and affect all ages.
It occurs when the gland is underactive, or becomes incapable of producing enough thyroid hormone or is improperly formed at birth, or surgically removed. Another common cause is Hashoimoto’s disease, an autoimmune disease where the antibodies of self, target the thyroid and destroy its thyroid hormone secreting ability. Symptoms of hypothyroidism usually go along with a slowdown in metabolism, and can include fatigue, feeling sluggish and lethargic, weight gain, depression, irregular menstrual cycles, trouble conceiving a baby, and mood changes, among others.
An overactive thyroid gland produces too much thyroid hormone, and a person is said to be hyperthyroid. The most common cause of hyperthyroidism is the autoimmune condition known as Graves’ disease, where antibodies target the gland and cause it to speed up hormone production. Symptoms include Fatigue or muscle weakness, anxiety, mood swings, rapid heartbeat, palpitations, insomnia.
Thyroid disease in pregnancy
Thyroid dysfunction can affect the health of the mother and the child before and after delivery. Untreated thyroid dysfunction in pregnancy has adverse effects on fetal and maternal well-being. The deleterious effects of thyroid dysfunction can also extend beyond pregnancy and delivery to affect neuro-intellectual development in the early life of the child. Demand for thyroid hormones is increased during pregnancy, which may cause a previously unnoticed thyroid disorder to worsen. Therefore, it is recommended that women at high-risk for thyroid disease should be tested early in their pregnancy.
Thyroid cancer is a cancer originating from follicular or parafollicular thyroid cells. Treatment involves surgical removal of thyroid gland (thyroidectomy) followed by radioactive iodine ablation and TSH-suppression therapy.
What are Thyroid function tests?
Different types of thyroid function tests are available. It is important to remember that interpretation of these tests is complicated as various conditions can alter the level of these hormones. These tests are always person specific and there is no common test recommended. Nevertheless, the common function test is to measure the levels of TSH in the blood.
In people with hypothyroidism (underactive thyroid) the amount of TSH will usually be high. This is usually because the thyroid is not making enough T3 to stop the pituitary producing TSH (see the chart). If the level of TSH is high, you will usually have further tests to check the levels of T3 and T4 in the blood.
In people with hyperthyroidism (overactive thyroid) the level of TSH will usually be low. This is usually because the thyroid gland is making too much of its hormones. When levels of T3 and T4 are high, the pituitary is ‘turned off’ and the amount of TSH produced is less. If you are found to have low levels of TSH you may have some more blood tests to check the levels of T3 and T4 in the blood. These tests may help doctors to find a specific cause of the low TSH.
More information on Thyroid disease and related research can be found here
Further Interesting links on Thyroid research: