Thyroid function & iodine

• What is the primary function of the thyroid gland?

  The thyroid gland releases thyroid hormones (T3 and T4) that regulate metabolism, including increasing basal metabolic rate, thermogenesis, oxygen consumption, and cardiac output.
• What are the components of the thyroid hormones T3 and T4?

  T3 (Triiodothyronine) contains 3 iodine atoms, while T4 (Thyroxine) contains 4 iodine atoms. Both hormones are synthesized from iodine trapped by the thyroid gland.
• How does the thyroid gland release T3 and T4 hormones?

  TSH (Thyroid Stimulating Hormone) stimulates the thyroid gland, causing T3 and T4 to be released into the blood after being synthesized and stored in the colloid within thyroid follicles.
• What is the role of iodine in thyroid hormone synthesis?

  Iodine is essential for the synthesis of thyroid hormones. The thyroid gland traps iodine from the diet to produce T3 and T4. A daily iodine intake of 100-250 μg is required for proper thyroid function.
• What happens to T4 after it is released into the bloodstream?

  Once released into the bloodstream, T4 binds to thyroxine-binding proteins. It is then converted to T3 in target cells, as T3 is the more biologically active form.
• How do thyroid hormones regulate metabolism?

  Thyroid hormones increase metabolic rate by enhancing glucose oxidation, which produces CO2, metabolic water, and ATP. This boosts energy production, increases oxygen consumption, and promotes heat production (thermogenesis).
• What receptors do thyroid hormones bind to in target cells?

  • T3 binds to high-affinity thyroid hormone receptors (TR) in the nucleus of target cells. This binding regulates gene expression, leading to protein synthesis and metabolic changes.
• What is the role of TSH and TRH in thyroid hormone regulation?

  TSH from the anterior pituitary gland stimulates the thyroid to produce and release T3 and T4. TRH (Thyroid Releasing Hormone) from the hypothalamus regulates the release of TSH, thus controlling thyroid hormone production
• What are the effects of thyroid hormones on body systems?

  Thyroid hormones increase basal metabolic rate, oxygen consumption, thermogenesis, and energy production. They also play a critical role in growth and development, particularly in children and fetal development.
• What is the result of iodine deficiency on thyroid function?

  Iodine deficiency can lead to hypothyroidism and developmental issues, including irreversible brain damage in children and impaired brain function in adults. It can also cause goiter (enlarged thyroid) due to the thyroid being stimulated to produce more hormones
• What is hypothyroidism and what are its symptoms?

  Hypothyroidism is a condition where the thyroid does not produce enough thyroid hormones. Symptoms include fatigue, weight gain, cold sensitivity, slow heart rate, dry skin, and developmental issues like low IQ and hearing loss in children.
• What is hyperthyroidism and what are its symptoms?

  Hyperthyroidism occurs when the thyroid produces too much thyroid hormone. Symptoms include rapid heart rate, weight loss, heat intolerance, anxiety, sweating, and enlarged thyroid (goiter)
• What is the cause of Graves' disease?

  Graves' disease is an autoimmune disorder in which antibodies mimic TSH and stimulate the thyroid to release excess T3 and T4. This leads to symptoms like an enlarged thyroid, bulging eyes (exophthalmos), heat intolerance, and anxiety.
• What is myxedema and what causes it?

  Myxedema is a form of postnatal hypothyroidism caused by thyroid or iodine deficiency or autoimmune conditions like Hashimoto’s thyroiditis. It results in facial swelling, cold sensitivity, weight gain, lethargy, and dry skin.
• What is congenital iodine deficiency syndrome and what are its symptoms?

  Congenital iodine deficiency syndrome is caused by iodine deficiency during pregnancy and leads to developmental issues such as brain damage, hearing loss, impaired speech, low IQ, muscle rigidity, and slow movement
• How do thyroid hormones affect growth and development?

  Thyroid hormones are essential for normal growth and development, particularly in fetuses and children. They promote the development of the fetal skeleton and nervous system. A deficiency can result in developmental delays and cognitive impairments.
• What are the actions of thyroid hormones in cells?

  In cells, T3 enters the nucleus and binds to thyroid hormone receptors (TR). This releases co-repressors and activates co-activators, regulating gene expression and enhancing protein synthesis.
• How does cold affect thyroid hormone release?

  Cold, particularly in children, stimulates the hypothalamus to release TRH (Thyroid Releasing Hormone), which in turn promotes the release of thyroid hormones (T3 and T4) from the thyroid, increasing metabolic rate and heat production.
• What are the signs and symptoms of hypothyroidism in children?

  In children, hypothyroidism due to iodine deficiency can lead to hearing loss, low IQ, speech difficulties, muscle rigidity, bradykinesia (slow movement), and other developmental issues.
• How do thyroid hormones contribute to heat production?

  Thyroid hormones contribute to heat production by increasing metabolic rate and promoting thermogenesis in tissues such as muscle and brown adipose tissue. This process generates heat in response to cold.