The thyroid gland is located just below the cartilage called the Adam's apple in our neck and in front of the trachea. It is butterfly shaped. It is also known as shield cloth due to its shape. It has two parts, right and left. These are called thyroid lobes. These two lobes are connected to each other by a thin band of tissue called the isthmus. The thyroid gland is as hard as a muscle. Therefore, it can be easily examined manually by the doctor. Its weight is about 20 grams. In some cases, it grows and exceeds its normal weight. This condition is called goiter.
When the thyroid gland is examined under a microscope, it is seen that it consists of formations called follicles. Follicles are round in shape and their edges consist of follicle cells and their middle consists of a substance called colloid in gelatin nature. Since the synthesized hormones are accumulated in colloid, this substance forms the reservoir of thyroid hormones.
WHAT ARE THE FUNCTIONS OF THE THYROID GLAND?
The function of the thyroid gland is to produce T3 and T4 hormones. There are 4 iodine atoms in each molecule of the T4 (Thyroxine) hormone. There are 3 iodine atoms in each molecule of the T3 (Triiodothyronine) hormone. The raw material of these hormones is the iodine atom. The thyroid gland produces T3 and T4 using the iodine atom. T4 hormone is actually the storage form of the most effective T3 hormone. The T4 hormone turns into the main effective T3 hormone by releasing an iodine atom before entering the cell where it will be active.
WHAT DO THYROID HORMONES DO?
Thyroid hormones. It regulates the functions of every cell and tissue in our body. Thus, thyroid hormones determine the speed of the entire metabolism. To be healthy, thyroid hormones must be secreted continuously and in sufficient amounts. Secretion in small amounts causes body functions to slow down, while secretion in large amounts causes body functions to accelerate. After the hormones produced in the thyroid gland pass into the blood, 99% of them circulate by binding to carrier proteins. These proteins are called thyroxine binding globulins (TBG). However, these hormones must be released in order to show their effects in the tissues. Free hormones constitute 1% of the total hormones in the body. In blood thyroid hormone measurements, bound and free hormones are generally measured together (total T4 and T3) or only free (free hormones). T4 and T3) are measured.
HOW ARE THYROID HORMONES SECRETED ACCORDING TO NEED?
Thyroid hormones. It is secreted and controlled by a system called "negative feedback mechanism". According to this mechanism, TRH hormone is secreted in the region of the brain called hypothalamus. This hormone acts on the pituitary gland and causes the secretion of TSH. TSH acts on the thyroid gland, causing the production and secretion of T4 and a small amount of T3. Most of T4 and T3 bind to proteins in the blood, and a very small part circulates freely in the blood. After these hormones reach a certain level, they put pressure on the hypothalamus and pituitary and stop the secretion of TRH and TSH. When the hormones decrease as a result of use, the pressure disappears, TRH and TSH are secreted again, and thyroid hormones are produced again according to the body's needs. The state of secretion of thyroid hormones in less than necessary amounts is called hypothyroidism, and the state of secretion in excessive amounts is called hyperthyroidism.
WHERE IS IODINE FOUND, HOW MUCH IS THE NEED FOR IODINE?
Iodine in general It is found in high amounts in seafood, in smaller amounts in milk, eggs and meat, and in very small amounts in vegetables and fruits. Many people also need a very small amount of iodine.
The daily iodine requirement determined by WHO (World Health Organization) is as follows:
- For children aged 0-59 months: 90 micrograms/ day,
- Between 6-12 years of age: 120 micrograms/day
- In young adults and adults: 150 micrograms/day
- Pregnant women and during breastfeeding: 200 micrograms/day day
According to some organizations, the amount of iodine in pregnant women and during breastfeeding is increased up to 220 and 290 micrograms/day, respectively.
The daily need is much higher in those with insufficient thyroid gland. It is very difficult to measure the amount of iodine in food. Whether sufficient iodine is consumed or not is determined by measuring the amount of iodine in the urine. Because most of the iodine taken is excreted in urine, and a very small amount is excreted in feces. In areas where there is no iodine deficiency, urinary iodine excretion is at least 100 micrograms/day, and in areas with iodine deficiency it is 3-45 micrograms/day. In practice, collecting 24-hour urine is quite difficult. Therefore, as an alternative, the ratio between iodine and creatinine can be calculated. r.
In cases where sufficient iodine cannot be taken (for example, in the Eastern Black Sea Region), thyroid hormone deficiency occurs. Hormone deficiency causes TSH secretion from the pituitary through a mechanism called feedback regulation mechanism. TSH stimulates the thyroid to produce adequate amounts of thyroid hormone. But since the thyroid gland cannot respond to the need, TSH's stimulation of the thyroid for a long time causes the thyroid cells to grow and multiply. This causes the volume of the thyroid to increase, thus causing goiter formation. Glaciers or continuous rainfall remove iodine from the soil, causing iodine deficiency in growing vegetables and fruits. Goiter occurs in people who eat these foods. By adding iodine to the salt of these patients (iodine supplementation), their goiter shrinks.
Iodine deficiency in pregnant women prevents the baby's brain development and causes hypothyroidism. As a result, irreversible mental retardation occurs in the brain.
Diseases that occur due to iodine deficiency are referred to as Iodine Deficiency Diseases. These diseases can be summarized as follows:
In pregnancy: Spontaneous miscarriage, stillbirth, congenital anomaly, disease in babies during pregnancy and after birth, endemic dwarfism.
In the newborn: Goiter, overt and subclinical hypothyroidism. , dwarfism.
In children and young adults: Goiter, subclinical and overt hypothyroidism, mental retardation, physical development disorder.
In adults: Goiter and its complications, hypothyroidism, mental retardation, increased infertility, Spontaneous hyperthyroidism, increased sensitivity to radiation.
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