Tyroid Functions and Diseases

Tyroid Functions and Diseases

 

The thyroid is one of the glands of the hormonal system. This is a butterfly-shaped gland located at the front of the neck. The glands of the hormonal system control many functions in the body using chemicals called hormones. These hormones are released into the bloodstream, where they circulate and regulate the functions of specific organs and organ systems. Hormones produced by the thyroid regulate how the body's cells use energy and the "speed" of metabolism. This gland also affects the rate of hair and bone growth, body weight, temperature and energy levels, as well as the function of the heart and digestive system.

Thyroid disease is a very common endocrine disorder, particularly in women. Hypothyroidism, or underactive thyroid, is a condition in which the thyroid produces fewer hormones than necessary for normal body function. 

Thyroid problems can occur with certain types of cancer and after certain cancer treatments. People treated for Hodgkin lymphoma or a brain or spinal cord tumour are at increased risk of having thyroid problems. Those who received cancer treatment in childhood are at even higher risk. Thyroid disorders may appear in the first months or years after diagnosis and treatment.

Thyroid function

The thyroid produces hormones that participate in growth and mental development. They also help regulate metabolism, the chemical process that occurs in the body to make and use energy. The thyroid is controlled by the pituitary gland

Thyroid hormones There are type of thyroid hormones:

  • 1) Thyroxine (T4) this is the main hormone produced by the thyroid, and has little to no effect on stimulating basal metabolism. Indeed, T4 is converted into T3, which is the most active hormone. The conversion of T4 to T3 takes place in the liver, but also in other tissues. Several factors control the conversion of T4 to T3, depending on the needs of the body and the presence or absence of diseases
  • 2) Triiodothyronine (T3):  Most of the T4 and T3 present in the blood is transported by a protein, thyroxine-binding globulin. Only a small portion of T4 and T3 circulate freely in the blood. However, it is a free hormone that is active.
When the free hormone is used by the body, some of the bound hormone is released by the binding protein. To make thyroid hormones, the thyroid needs iodine, an element found in water and food. The thyroid captures iodine and integrates it into its cells for the synthesis of thyroid hormones.
When thyroid hormones are used, a small portion of their iodine is released and returns to the thyroid, where it is reused to make other thyroid hormones. Interestingly, the thyroid releases slightly fewer hormones if it receives high levels of iodine through the blood.
The thyroid also secretes calcitonin, a hormone which helps maintain bone mass by promoting the fixation of calcium in the bones.

What are the symptoms of a thyroid problem?

Hyperthyroidism (excessive production of hormones by the thyroid) may cause some or all of the following symptoms:

  • Restlessness
  • Nervousness
  • Emotionality
  • Irritability
  • Trouble sleeping
  • Hyperactivity Hand tremor.
  • Weight loss despite increased appetite.
Symptoms include thin, brittle nails and hair, weight gain, fatigue, decreased heart function, constipation, and feeling cold. Hyperthyroidism, or thyrotoxicosis, is a condition in which the thyroid produces too many hormones. Symptoms include hair loss, weight loss, increased heart rate, nervousness, frequent bowel movements, sweating, and irregular periods in women. The doctor can diagnose thyroid disease by assessing the patient's symptoms, palpating the neck to assess changes in the thyroid, and performing blood tests to determine circulating thyroid hormone levels.

    What is thyroid disease?

    Hyperthyroidism, or thyrotoxicosis, is a condition in which the thyroid produces too many hormones. Symptoms include hair loss, weight loss, increased heart rate, nervousness, frequent bowel movements, sweating, menstrual irregularities

    Blood tests linked to thyroid function

    To assess the proper functioning of the thyroid, doctors generally measure hormone levels in the blood. They measure the following rates:

    • TSH The TSH level in the blood is generally the best indicator of thyroid function. As the role of this hormone is to stimulate the thyroid, its level in the blood is typically high when the thyroid is working insufficiently (hypothyroidism), and therefore needs to be more stimulated, and decreases when the thyroid is working excessively (hyperthyroidism), and therefore needs to be less stimulated. However, in rare cases where the pituitary gland is not functioning normally, the TSH level does not reliably reflect thyroid function. When a person is examined for a thyroid problem, TSH is always measured, and sometimes other tests are done as well. Additionally, for people with insufficient thyroid function (hypothyroidism) who are treated with thyroid hormones as medication, TSH is usually measured one or more times a year to check whether the medication dose needs to be adjusted.
    • T3 or T4 : When doctors measure the levels of thyroid hormones T4 and T3 in the blood, they usually measure the bound and free forms of each hormone (total T4 and total T3).  The majority of circulating levels of T4 and T3 are linked to a protein called thyroxine-binding globulin. If the thyroxine-binding globulin level is abnormal, total thyroid hormone levels may be misinterpreted; This is why doctors sometimes measure only the levels of free thyroid hormones in the blood (free T4 and free T3). Levels of thyroxine-binding globulin are lower in people with kidney disease or conditions that reduce protein synthesis by the liver, or in those taking anabolic steroids. The rate is higher in pregnant women, those taking oral contraceptives or other forms of estrogen, and in the early stages of hepatitis.

     

    Thyroid ultrasound:   When one or more masses (nodules) are palpated in the thyroid, an ultrasound can be performed. Ultrasound uses sound waves to measure the size of the gland and determine whether the growth is solid or fluid-filled (cystic), what the characteristics of the nodule are, such as the presence or absence of calcium, and the number and the prominence of blood vessels in the thyroid.

    Radioactive iodine: In another test (radioactive iodine uptake test, a type of scan), a small amount of a radioactive substance (such as iodine or technetium) is injected into the blood stream. The radioactive substance concentrates in the thyroid and a device (gamma camera) performs another type of examination which detects the radiation and produces an image of the thyroid which will show any physical abnormalities. As the amount of radioactive iodine picked up by the thyroid depends on the functioning of the thyroid, a thyroid scan also helps determine whether the functioning of a part of the thyroid is normal, increased or decreased, compared to the rest of the gland.

    Other thyroid tests: If doctors suspect an autoimmune disease, a blood test is done to detect possible antibodies that attack the thyroid. If thyroid cancer is suspected, doctors take a sample of thyroid tissue using a small needle to analyse it (biopsy). Doctors usually perform an ultrasound to identify the biopsy site. If medullary thyroid cancer is suspected, the blood level of calcitonin is measured, because these cancers always secrete calcitonin.

    Thyroid disease Video Screening for thyroid disorders Some specialists recommend screening for thyroid disease by measuring blood TSH levels every year or every few years in people over 70. However, a number of professional medical societies that have examined this issue recommend against screening asymptomatic adults to avoid over treating people with minor biological abnormalities. Screening is recommended for all newborns to detect hypothyroidism (congenital hypothyroidism), which can cause major malformations in the developing brain and other organs if left untreated.

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