Endocrine Health - Thyroid Flashcards
Q: What hormone does the hypothalamus release to stimulate TSH release from the anterior pituitary?
A: The hypothalamus releases thyrotropin-releasing hormone (TRH).
Q: What role does TSH play in thyroid function?
A: TSH stimulates the thyroid to produce T4 (thyroxine) and T3 (triiodothyronine).
Q: What is the role of iodothyronine deiodinases in the thyroid?
A: They are enzymes that convert T4 to the active T3 or the inactive reverse T3 (RT3), regulating thyroid hormone activity.
Q: What is T3, and how does it compare to T4 in terms of potency?
A: T3 (triiodothyronine) is about four times more potent than T4 and is active in increasing growth, metabolism, heart rate, and development.
Q: What percentage of thyroid hormone released by the thyroid is T4?
A: About 90% of the thyroid hormone released by the thyroid is T4.
Q: What is reverse T3 (RT3) and its function?
A: Reverse T3 is a biologically inactive form of T3 that protects tissues from excess thyroid hormones.
Q: Which two nutrients are essential for thyroid hormone synthesis?
A: Tyrosine and iodine are essential, as they form the backbone of T3 and T4 synthesis.
Q: Why is selenium important for thyroid function?
A: Selenium acts as a cofactor for enzymes involved in the conversion of T4 to T3 and supports antioxidant functions.
Q: What vitamins support thyroid hormone synthesis and function?
A: Vitamins A, C, E, B2, B3, B6, and B12 are all supportive of thyroid synthesis and function.
Q: List some iodine-rich foods that support thyroid health.
A: Sea vegetables, ocean fish, shellfish, eggs, and dairy products are rich in iodine.
Q: What can cause iodine deficiency, increasing the risk of thyroid disorders?
A: Low/no dairy or fish intake, pregnancy, vegan diets, and high intake of goitrogenic foods can lead to iodine deficiency.
Q: What is the Wolff-Chaikoff effect?
A: It is a response that temporarily inhibits thyroid hormone production in the presence of excess iodine, potentially leading to hypothyroidism in certain individuals.
Q: Where does most of the T3 in circulation come from?
A: About 90% of circulating T3 comes from peripheral conversion of T4, not direct thyroid secretion.
Q: What is the biological role of reverse T3 (RT3)?
A: RT3 is inactive but can bind to T3 receptors, blocking T3’s action when levels are elevated, especially in cases of high stress or chronic illness.
Q: What factors can increase the conversion of T4 to RT3?
A: Chronic illness, high stress, deficiencies in zinc, selenium, or iron, liver dysfunction, and fasting can increase RT3 conversion.
Q: Name some environmental disruptors that can interfere with thyroid function.
A: Pesticides, PCBs, bisphenols (e.g., BPA), phthalates, and perchlorates are common disruptors of thyroid function.
Q: How does fluoride affect thyroid function?
A: Fluoride can interfere with iodine uptake and the conversion of T4 to T3, potentially lowering thyroid function.
Q: What are some ways to avoid HPT disruptors?
A: Use filtered water, avoid fluoride toothpaste, eat organic foods, and avoid plastic packaging and farmed fish.
Q: Which types of medications may decrease TSH secretion?
A: Dopamine, glucocorticoids, and lithium can decrease TSH secretion.
Q: How do beta-blockers affect T4 to T3 conversion?
A: Beta-blockers can reduce the conversion of T4 to the active T3.
Q: Why is it important to review a patient’s medication history during a thyroid assessment?
A: Many medications can alter thyroid function by affecting TSH secretion, T4 and T3
Q: How does gut dysbiosis affect thyroid function?
A: Gut dysbiosis can negatively impact thyroid function by altering iodine uptake, thyroid hormone metabolism, and increasing inflammation in autoimmune thyroid disease (AITD) through changes in intestinal permeability.
Q: What is a common marker of intestinal permeability associated with AITD?
A: Elevated zonulin levels, which are often linked to increased intestinal permeability, are commonly seen in AITD.
Q: What are the optimal conventional medicine ranges for TSH and Free T4?
A: The optimal range for TSH is 0.4 to 2.5 mIU/L, and for Free T4, it is 12.8 to 19.5 pmol/L.
Q: Which antibody tests are commonly used to diagnose autoimmune thyroid disorders?
A: Thyroglobulin antibodies and thyroid peroxidase (TPO) antibodies are commonly tested.
Q: Why is it important to assess both clinical symptoms and test results in thyroid function testing?
A: Blood tests may not always reflect tissue levels of T3; therefore, clinical signs and symptoms are crucial for a comprehensive assessment.
Q: What thyroid disorder is suggested by high TSH and normal T4 and T3 levels?
A: High TSH with normal T4 and T3 suggests subclinical hypothyroidism.
Q: What findings are typically seen in hypothyroidism and hyperthyroidism regarding TSH, T4, and T3?
A: Hypothyroidism often shows high TSH with low T4/T3, while hyperthyroidism often shows low TSH with high T4/T3.
Q: What test is commonly used to assess iodine status in the body?
A: A urine iodine test is commonly used to measure iodine levels.
Q: What is the optimal urinary iodine level in children and adults?
A: The optimal urinary iodine level for children and adults is 100–199 mcg/L.
Q: What does the Barnes Basal Body Temperature Test measure, and how is it performed?
A: It measures basal body temperature as an indicator of low thyroid function. The test is performed by taking axillary temperature daily for seven days upon waking.
Q: What temperature reading might indicate low thyroid function in the Basal Body Temperature Test?
A: A waking temperature consistently below 36.5°C may indicate low thyroid function.
