Where is thyroid gland located and its function?
Thyroid is a butterfly shaped organ located in front of the neck, just below the voice box. It consists of two lobes, one on each side of the windpipe and is one of the largest endocrine glands in our body. In a normal adult, the thyroid gland weighs 15 to 25 grams. Just like every other organ in our body, thyroid gland has a specific function and role to play; infact, it is known to function even before birth. Thyroid gland functions to regulate the metabolism of our body by producing hormone that facilitate energy production.
The Facts behind the Gland
The thyroid gland is a component of the endocrine system that is, it produces hormones that are released into circulation. These hormones then travel to different cells and tissues in the body, where they play a wide variety of roles, primarily associated with cellular metabolism. Though first christened in 1656 by Thomas Wharton, the disorders of the thyroid especially its enlargement causing neck swelling, have been known long before then. It is surprising then, to know that the first successful isolation of a thyroid hormone and its identification was only done in 1914 by Kendall and Osterberg. They named it "Thyroxine", which today, is also colloquially called as T4 (thyroxine). Since then, we have developed our understanding of thyroid hormones, their functions in the body as well as disease conditions associated with thyroid gland and its hormones. The thyroid gland is located on the front part of the neck below the thyroid cartilage (Adam's apple) and releases two hormones triiodothyronine (triiodothyronine (T3)) and thyroxine (T4). These are iodine-containing hormones, among which T4 is the main hormone. At the site of action, i.e., inside the cells, one iodine is removed, leading to the formation of T3.
Thyroid hormones are important for regulating metabolic processes. These are processes that are responsible for energy production in the cell, as well as the formation and breakdown of proteins, LDL-bad cholesterol, carbohydrates and nucleic acids. These hormones are synthesized by thyroid follicular cells from thyroglobulin and stored in the thyroid follicle. The synthesis and release of thyroid hormones is stimulated by another hormone produced by the pituitary, called thyroid stimulating hormone (Thyroid Stimulating Hormone (TSH)), which acts like a regulating switch, turning on thyroid function when required and turning it off when not.
Mastermind behind many Functions
Thyroid hormones carry out a large number of functions in the body. Some of these include:
Metabolism Normal growth and development requires Metabolic processes that generate energy for the cells to utilize. These metabolic processes also provide the biomolecules that are required by the cells. Basal metabolic rate (BMR) is a unique rate at which the body expends energy at rest. Thyroid hormones play a role in stimulating BMR by increasing the breakdown of ATP molecules which results in the generation of energy. It also stimulates the pathways that involve breakdown and synthesis of carbohydrates, fats and liver.
Maintaining body temperature Maintaining body temperature requires generation of heat continuously, with more heat produced on exposure to cold, after eating or after energy expenditure. Thyroid hormones are required for the maintenance of core body temperature.
Regulation of body weight As thyroid hormones are required for regulation of fat metabolism, cholesterol synthesis and transport as well as breakdown into bile, thyroid hormones indirectly do impact body weight. These hormones stimulate breakdown of lipids directly, reducing triglycerides and LDL-bad cholesterol (including LDL) levels.
Production and action of insulin The development and function of pancreatic cells is stimulated by thyroid hormones. As these cells are responsible for the production of insulin, thyroid hormones are important for maintaining normal blood glucose levels.
The thyroid gland has other functions such as calcium homeostasis and bone remodeling. It also produces the hormone calcitonin which decreases the amount of calcium released from the bone. Thyroid hormones are also responsible for maintaining heart rate, as well as blood flow.
What hormones are secreted by the thyroid gland and their functions?
The T Hormones Thyroid secretes two metabolically important hormones, called Triiodothyronine (T3) and Thyroxine (T4). These two horm- ones, control various metabolic activities essential for energy, growth and development of the body. These two hormones are required every minute by every cell, tissue and organ. Their secretion is highly regulated and any fluctuation in the levels can result in health complications.Check your Thyroid at home
How does iodine affect the thyroid?
lodine: The key entity Thyroid hormones are made using iodine by the thyroid gland and hence plays a crucial role in thyroid functioning. lodine defi- ciency affects thyroid hormone production, causing decrease in their levels. lodine is obtained from dietary intake, which in turn, depends on its content in the soil and water in a particular locality. Studies of a locality may indicate the need for suppl- ementation of iodine in salt and bread. In India, 30 - 40% of the area is known to be iodine deficient.
How is TSH produced?
TSH - Thyroid's remote control The pituitary gland also known as the 'Master gland' secretes a hormone called Thyroid Stimulating Hormone (TSH), which acts on the thyroid specifically and directly. TSH stimulates and controls various steps involved in synthesis and secretion of the thyroid hormones. TSH senses the existing thyroid hormone levels and works as required, to maintain the desired levels, by stimulating or leaving without stimulation. The secretion of TSH is yet again controlled by another hormone namely TSH - releasing hormone (TRH) which is secreted by the hypothalamus .
What are the different thyroid disorders?
There are basically 2 types of Thyroid Disorders
1. Anatomical Goiter is a disorder characterised by an abnormal size and structure of the thyroid gland. Goiter may be with nodules and may or may not have any associated disorder.
What are the main causes of goiter?
An enlarged thyroid gland, with or without nodules, is called a Goiter. A nodule is the enlargement of a part of the gland. Goiter develops over a period of time and can be as big as 2 to 10 times the size of a normal thyroid gland. Any abnormal enlargement or swelling in the region of the thyroid should be medically evaluated to rule out the possibility of cancer.
What is the most common thyroid disorder?
Considering the wide variety of functions that are carried out by the thyroid hormones, it is
evident that any imbalance in its levels causes effects ranging wide. The most common disorders
related to the thyroid gland are
Hypothyroidism Hypothyroidism is a condition in which the thyroid gland is unable to produce sufficient amounts of thyroid hormones. It is of two types- primary and secondary. Primary hypothyroidism occurs due to failure of thyroid gland function. Secondary hypothyroidism results from insufficient stimulation of thyroid gland by thyroid stimulating hormone, or reduced stimulation of the pituitary gland to produce TSH. Almost 50% of primary hypothyroidism cases arise due to autoimmune reaction against the thyroid gland, and is more frequent in women than men. Another common cause of hypothyroidism is iodine deficiency. As iodine is required for synthesis of thyroid hormones, its paucity can cause hypothyroidism.
Symptoms of hypothyroidism
- Delayed development
- Hair loss
- Unexplained weight gain
- Impaired memory
Hyperthyroidism This condition is characterized by increased synthesis and release of thyroid hormones. Some of the causes of hyperthyroidism are Graves' disease, goiter, and some tumors. Graves disease is one of the most common causes of hyperthyroidism. It is also an autoimmune condition where the thyroid gland is activated into producing thyroid hormones when antithyroid antibodies bind to receptors that are meant for TSH. This activates the signaling pathway of TSH, resulting in increased production of thyroid hormones. A type of goiter, called as toxic multinodular goiter is characterized by the formation of multiple nodules on the thyroid gland. If a single nodule is formed, it is called as toxic adenoma.
Symptoms of Hyperthyroidism
- Hyperactivity, restlessness, irritability
- Unplanned weight loss
- Hair fall
- Muscle weakness
- Intolerance to heat
Trouble to Thyroid Hormone is a Trouble to You Thyroid gland plays a major role in a woman's reproductive health. Different types of thyroid disorders affect either its structure or function signifying various effects on the woman's body.
EFFECTS OF THYROID DISORDERS IN FEMALE
Thyroid disorder can cause abnormally delayed or early puberty and menstruation. Elevated levels of thyroid hormones are responsible for low or heavy menstruation, for irregular menstrual periods or its absence (condition called amenorrhea).
Reproduction Ovulation can be affected due to overactive or underactive thyroid. Thyroid disorder inhibits the occurring of ovulation and may also increase the risk of developing cysts in the ovaries if a woman has hypothyroidism. Milk production in the breast in nonpregnant women is seen in case of severe hypothyroidism.
Pregnancy & postpartum Pregnant woman with underactive thyroid can suffer from miscarriage, preterm delivery, stillbirth, etc. Women with overactive thyroid are at risk of having more severe morning sickness. Thyroid disorders during pregnancy can also lead to conditions such as postpartum thyroiditis (thyroid problems in the mother after birth).
Menopause Thyroid disorders may cause early onset of menopause before the age of 40 or at early 40s. There are chances of mistaking symptoms of hyperthyroidism as early menopause, which include lack of menstruation, hot flashes, inability to sleep (insomnia) and mood swings.
Patients having autoimmune disorders may have more than one organaffected. With chronic thyroiditis,
there is a higher incidence of other
autoimmune diseases such as:
blood sugar Mellitus
10% of patients with type 1 - diabetes develop chronic thyroiditis, which may change insulin requirements. It is therefore essential for Diabetes patients to be checked for goiter and have their TSH levels monitored regularly. Some patients suffering from depression have primary hypothyroidism. Lithium may induce goiter and hypothyroidism.
Complications related to
Hypothyroidism can cause complications in many like delayed or scanty menstrual periods and unexplained Infertility or mis- carriages, particularly early in Pregnancy. Therefore, thyroid function tests are often a routine in evaluating a patient who may have problems with pregnancy. In men, untreated hypothyroidism is known to cause disturbances in sex and fertility. In women, adjustment of thyroid hormone levels are known to improve menstrual pattern and increase the probability of fertilisation.