Which organ secretes thyroxine and triiodothyronine

T4 is believed to be a pro-hormone and a reservoir for the more active and main thyroid hormone T3. T4 is converted as required in the tissues by iodothyronine deiodinase. Thyroid hormone : Diagrammatic representation of thyroid hormone synthesis in a thyroid follicle. If there is a deficiency of dietary iodine, the thyroid will not be able to make thyroid hormone. A lack of thyroid hormone will lead to decreased negative feedback on the pituitary, which in turn, will lead to increased production of thyroid-stimulating hormone, which causes the thyroid to enlarge goiter.

The primary function of the thyroid is to produce the hormones triiodothyronine T3 , thyroxine T4 , and calcitonin. Triiodothyronine T3 and thyroxine T4 are enzymes produced by the thyroid gland.

T4 is thought to be a pro-hormone to the more metabolically active T3. T4 is converted to T3 in tissues as required by deiodinase enzymes. Calcitonin is another hormone released by the thyroid gland that is responsible for modulating blood calcium levels in conjunction with parathyroid hormone, which is released from the parathyroid.

The main activity of the thyroid hormones T3 and T4 is to boost the basal metabolic rates of proteins, fats, and carbohydrates as well as vitamins. Thyroid system : An overview of the thyroid system. Thyroid hormones affect the dilation of blood vessels, which in turn affects the rate at which heat can escape the body.

The more dilated blood vessels are, the faster heat can escape. A person who suffers from hyperthyroidism an over-active thyroid will experience a fever; conversely, a person who suffers from hypothyroidism a less active thyroid will experience a decrease in body temperature.

The cells of the developing brain are a major target for T3 and T4. Thyroid hormones play a particularly crucial role in brain maturation during fetal development by regulating actin polymerization during neuronal development. In the blood, T4 and T3 are partially bound to thyroxine-binding globulin TBG , transthyretin, and albumin. Only a very small fraction of the circulating hormone is free—T4 0. Only the free fraction has hormonal activity. As with the steroid hormones, thyroid hormones are lipophillic and can cross the cell membrane and bind to intracellular receptors, which act alone as transcription factors or in association with other factors to modulate DNA transcription.

The production of thyroxine and triiodothyronine is regulated by thyroid-stimulating hormone TSH that is released from the anterior pituitary. The production of thyroxine T4 and triiodothyronine T3 is primarily regulated by thyroid-stimulating hormone TSH that is released from the anterior pituitary gland.

This results in increased metabolism, growth, development and the activation of numerous other systems controlled by thyroid hormones. Thyroid hormones also provide negative feedback to the hypothalamus and anterior pituitary gland. The thyroid system : Thyroid hormones are produced from the thyroid under the influence of thyroid-stimulating hormone TSH from the anterior pituitary gland, which is itself under the control of thyroptropin-releasing hormone TRH secreted by the hypothalamus.

This uncontrolled release of thyroid hormones causes hyperthyroidism for a few weeks or months. It may occur in women after childbirth.

In contrast to iodine deficiency, excessive iodine intake may have negative effects on your thyroid. Excessive iodine is found in a number of drugs such as Amiodarone, Lugol's solution iodine and some cough syrups. This might cause the thyroid to produce either too much or too little hormone in some individuals. The before mentioned problems affect the production of thyroid hormone either too much or too little.

However, problems concerning the thyroid gland can be very distinct. Swelling and lumps can occur within the thyroid gland. Such nodules can be harmless, but some can cause the production of hormones or even be cancerous.

In some cases, such as cancer, the thyroid is removed. You can live without your thyroid, but you need to take medicine daily to substitute the hormones produced by your thyroid gland. Iodine is most essential to maintain a healthy thyroid.

Nonetheless, the daily and constant supply of this micronutrient is important. Too much iodine at once is counter-productive and causes your thyroid to produce less hormones. The best way to get your daily dose of iodine is through eating healthy foods like seafood and dairy products. In addition, iodized salt is a good source and you can use it to season your food.

Nowadays, iodine is added to salt to combat goitres caused by hypothyroidism. About Contact Events News. Search Search. You and Your Hormones. Students Teachers Patients Browse. Human body. Home Glands Thyroid gland. Thyroid gland The thyroid gland is part of the endocrine system and produces thyroid hormones, which are important for metabolic health.

Where is my thyroid gland? Thyroid Hormone Production and Function. Topic Overview The thyroid gland uses iodine from food to make two thyroid hormones: triiodothyronine T3 and thyroxine T4. When the hypothalamus and pituitary are working normally, they sense when: Thyroid hormone levels are low, so they secrete more TRH and TSH, which stimulates the thyroid to make more hormones. Thyroid hormone levels are too high, so they secrete less TRH and TSH, which reduces hormone production by the thyroid.

Disease or tumors of the pituitary gland can affect this process. Thyroid hormones affect every cell and all the organs of the body.

They: Regulate the rate at which calories are burned, affecting weight loss or weight gain. Can slow down or speed up the heartbeat. Can raise or lower body temperature. Influence the rate at which food moves through the digestive tract. Control the way muscles contract.