Endocrine System - The Thyroid Gland and Thyroid Hormone

Hello everyone, welcome to this post today. In my post, I will be writing about the thyroid gland. The thyroid gland is a butterfly-shaped endocrine gland that is located in the neck which is in proximity to the trachea, and inferior to the Larynx. It produces hormones that regulate the body's metabolism and energy levels in a way that when it is produced less, the body's energy and metabolism are reduced, and when it is at an increased rate, the rate of metabolism can increase above 60% above the normal level.

The thyroid gland, located inferior to the larynx and in proximity to the trachea is made up primarily of follicular cells which produce and secrete the thyroid hormone. In the brain, the hypothalamus which performs lots of functions including maintaining homeostasis sends signals to the pituitary gland which sends signals to the thyroid gland to secrete the thyroid hormone.

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The hypothalamus secretes the thyrotropin-releasing hormone (TRH) via the paraventricular nucleus into the hypophyseal portal system, then to the anterior pituitary where the thyrotropin reacts to the thyrotropin-releasing hormone (TRH) to secrete the thyroid-stimulating hormone (TSH). The thyroid-stimulating hormone is released into the blood vessels which then reaches the thyroid gland. The thyroid gland after receiving the hormone signal starts to produce and secrete the thyroid hormone Thiodothyronine hormones (T3) which insinuates that the hormone has three atoms of iodine and tetraiodothyronine (T4) which insinuates that the hormone has four atoms of iodine. The thyroid hormone is responsible for increasing the metabolism of many structures in the body. It is important to know that iodine deficiency can lead to the inability to secrete the hormone, and when children have this deficiency, it causes delayed or lagged growth and development. Adult humans need about 20mg to 50mg of iodine annually, and about 70-80% of the iodine is stored in the thyroid gland. In most countries where industrialized edible salt is produced, the salt contains iodine so taking iodine is now a normal part of daily food. The thyroid is transported in the blood through the thyroxin-binding globulin which then reaches different organs and tissues in the body.

Regulating the thyroid hormones is very important as it is a bad thing to have too few or too many types of a hormone being secreted. It is important to remember that hormones are secreted directly into the bloodstream. When the Thyroid Hormone levels are high, it will exert back to the hypothalamus, giving a negative feedback mechanism that will inhibit the paraventricular nucleus in the hypothalamus from producing and secreting thyrotropin-releasing hormone (TRH) which will inhibit the production of thyroid-stimulating hormone (TSH) and then lead to reduced thyroid hormone. When there is a low amount of Thyroid hormone in the body, it will send negative feedback to the hypothalamus which will cause the paraventricular nucleus to release more thyrotropin-releasing hormone (TRH), causing the increase in the production and secretion of thyroid-stimulating hormone (TSH) which will lead of the increase in the secretion of Thiodothyronine hormones (T3) and tetraiodothyronine (T4).

The thyroid hormone in the bone is important the in promotion of bone growth and maturation when in muscles, it promotes muscular function and the development of those muscles. In the body, it increases the basal metabolic rate, and the rate of oxygen usage, and promotes metabolic actions such as lipolysis, glycolysis, gluconeogenesis, and Lip density Low-density lipoprotein uptake. In the heart, the presence of thyroid hormone promotes cardiac output and promotes increases the synapses, myelination, and dendrite activity in the brain. It promotes motility and secretion of the gastrointestinal tract, as well as hydration of the skin.

Thyroid hormones affect the majority of the cells in the body by activating multiple genes causing the cell to build protein enzymes, a structural protein, and transport protein. They do this by increasing the size of the mitochondria which is the powerhouse of the cell, as it utilizes carbohydrates and lipids to produce ATP. The thyroid hormone, like I said above is responsible for stimulating all aspects of carbohydrate metabolism as well as the utilization of fat, as it pulls fats from its storage into the blood as free fatty acid which will then be utilized for energy creation. Thyroid hormones while increasing the utilization of fat, they lower the level of triglycerides and cholesterol in the blood. In cases of hypothyroidism where there is a low secretion of thyroid from the thyroid gland, it can lead to an increase in increase in cholesterol in the body which could lead to cardiovascular problems. Hyperthyroidism can also lead to certain cardiovascular conditions as it affects some cardiovascular structures. It can cause high heart rates which could lead to myocardial failure. It can also affect the guts as it would cause the gut to contract more forcefully leading to diarrhea. When a person has hyperthyroidism, the muscles in the body contract more vigorously and quickly, and in cerebral function, it can cause patients to experience anxiety, agitation, and paranoia. Hypothyroidism in males can lead to decrease sex drive and impotency for males, while in females it can cause irregularity in the menstrual cycle.

It is no doubt that the thyroid gland is very important in our day-to-day activities, but also it is good to remember that it is better to be not too low or too high as it can lead to health conditions.

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