| Thyroid gland | |||||
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The thyroid gland is an endocrine (or homone-producing) gland that is located at the base of the throat, just below where the Adam's apple is located on the trachea.
The thyroid is shaped like a butterfly, consisting of two main areas on the left and right (called lobes) of the trachea and which are joined in the middle at the trachea.
The thyroid can be easily felt upon examnation by a doctor.
The thyroid is controlled by the hypothalamus, which produces thyrotropic releasing hormone (TRH), that stimulates the anterior pituitary gland to produce the thyrotrophic stimulating hormone (TSH).
The TSH stimulates the thyroid to produce two hormones:
- T3 - tri-iodo-thyronine
This is the more active hormone, but is secreted in lesser quantity - T4 - thyroxine
This is the less active hormone, but it is secreted in greater quantity, most of which is converted into T3
The thyroid gland has special follicles (called para-follicular cells) that control the level of calcium in the blood (the parathyroid hormones also control this).
The thyroid gland secretes calcitonin when it samples the high levels of calcium in the blood passing through it. This has the effect of making the bones retain more of their calcium, decreaing the bone tissue breakdown and decreasing levels of calcium in the blood to normal levels.
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- The thyroid controls metabolism - how quickly the body uses up the energy from food taken in
- T3 and T4 hormones target most cells in the body to assist with process such as metabolism, protein synthesis, as well as growth and development
- Both T3 and T4 contain iodine and tyrosine molecules in their structural make-up
- The thyroid gland, together with the parathyroid glands, control the level of calcium in the blood
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Why the thyroid gland is important
The thyroid is really important to ensure the healthy working of many basic processes in the body, such as:
- Metabolism regulation
- Levels of glucose in the blood
- Energy production and usage
- Increases activity of adrenalin
The thyroid gland can stop working properly, due to various factors and the following conditions can occur:
- Goitre
- Hyperparathyroidism
- Hyperparathyroidism
references
- Marieb EM, Hoehn K. Human Anatomy & Physiology. 7th edition, 2006. Benjamin Cummings Publishing
- Tortora GJ, Derrickson BH. Principles of Anatomy & Physiology. 11th edition, 2005. Wiley Publishing
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