Thyroid Hormone
Mechanism: T4 is converted to T3, which binds nuclear thyroid hormone receptors and raises gene transcription, metabolic rate, heart rate and thermogenesis.
What our notes say
- Mechanism: T4 is converted to T3, which binds nuclear thyroid hormone receptors and raises gene transcription, metabolic rate, heart rate and thermogenesis. (Integrated case paper: Medicine, Surgery, Gynaecology and Paediatrics (160 marks)
- When it is caused by hypothyroidism, thyroid hormone treats it. (Year 6 Gynaecology CAT 1 (MBOG 6511): 13 December 2019, 4 short answers and 16 M)
- The TSH is low from negative feedback from the increased thyroid hormone production. (Chemical pathology and Endocrine pathology — Past Paper Questions & Answers)
- Distinguishing feature: thyroid hormone is stored extracellularly in colloid (Aponeurosis — Histology Question Bank)
- T3 is thyroid hormone, prolactin is pituitary hormone, and ADH is produced by the hypothalamus. (Chemical Pathology MCQs)
- Inflammation of the thyroid gland due to lymphocytic infiltration, causing stored thyroid hormones to be released into the circulation (Internal Medicine 4th Year Endocrinology CAT: 30 MCQs)
Study material on Thyroid Hormone
- LECTURE 4: Thyroid Hormones
- Thyroid Hormone
- Review Questions
- LECTURE 1: Principles of Endocrinology
- Medical Physiology Pp2 Year 2
- Endocrine and Metabolic Pathology MCQs: Practice Questions
- Chemical pathology and Endocrine pathology
- MBMP2300: Medical Physiology II MCQs
- MBMP2300: Medical Physiology II - Complete Study Guide
- Medical Physiology Paper II MCQs
- Thyroid Hormone Physiology and Pathology
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Practice questions on Thyroid Hormone
What is the role of dietary iodine in thyroid hormone secretion?
- Essential component for the synthesis of thyroid hormones (T3 and T4)
- Stimulates the release of TSH from the pituitary gland
- Inhibits the breakdown of thyroid hormones
- Regulates the sensitivity of thyroid hormones to target tissues
Answer: A. Iodine is a critical raw material required for the synthesis of thyroid hormones (thyroxine/T4 and triiodothyronine/T3) by the thyroid gland. Iodine atoms are incorporated into tyrosine residues within the thyroglobulin molecule.
Amount of dietary iodine in the control of thyroid hormone secretion
- Is essential for the synthesis of thyroid hormones
- Inhibits the release of TSH
- Stimulates the uptake of iodine by the thyroid gland
- Is unnecessary for thyroid hormone production
Answer: A. Dietary iodine is a critical component for the synthesis of thyroid hormones (thyroxine and triiodothyronine) by the thyroid gland. Without sufficient iodine, thyroid hormone production is impaired.
Amount of dietary iodine in the control of thyroid hormone secretion
- High iodine intake stimulates TSH secretion
- Low iodine intake leads to decreased T3 and T4 synthesis
- Iodine is a component of T3 and T4
- Iodine only influences thyroid stimulating hormone (TSH) secretion
Answer: C. Iodine is an essential component of the thyroid hormones thyroxine (T4) and triiodothyronine (T3). Without adequate iodine, the thyroid gland cannot synthesize sufficient amounts of these hormones, leading to hypothyroidism. While iodine intake does influence TSH secretion (e.g., Wolff-Chaikoff effect with high intake, or increased TSH with low intake to try to compensate), its direct role as a building block for thy
Amount of dietary iodine in the control of thyroid hormone secretion
- Essential component for synthesis of thyroid hormones
- Inhibits the release of TSH
- Stimulates the production of T3 and T4
- Has no role in thyroid hormone secretion
Answer: A. Iodine is an essential element required for the synthesis of thyroid hormones (thyroxine T4 and triiodothyronine T3). A deficiency in iodine leads to impaired thyroid hormone production.
Amount of dietary iodine in the control of thyroid hormone secretion
- Low iodine intake stimulates TSH production, leading to increased thyroid hormone synthesis and goiter.
- High iodine intake directly stimulates thyroid hormone synthesis.
- Iodine is a substrate for thyroid hormone synthesis.
- Iodine is a cofactor for T3 and T4 degradation.
Answer: C. Iodine is an essential component of thyroid hormones (thyroxine (T4) and triiodothyronine (T3)). The thyroid gland actively transports iodine from the blood to synthesize these hormones. A deficiency in dietary iodine leads to impaired thyroid hormone production, which in turn stimulates the pituitary gland to release more TSH, leading to thyroid enlargement (goiter) in an attempt to capture more iodine. High iodine
Amount of dietary iodine in the control of thyroid hormone secretion
- Essential component of thyroid hormones.
- Inhibits thyroid hormone synthesis.
- Stimulates the release of TSH.
- Degrades thyroid hormones.
Answer: A. Iodine is an essential component of both thyroxine (T4) and triiodothyronine (T3), the primary thyroid hormones. Without adequate iodine, the thyroid gland cannot synthesize sufficient amounts of these hormones, leading to hypothyroidism. While dietary iodine can indirectly influence TSH release due to feedback mechanisms on thyroid hormone levels, its direct role is as a building block for the hormones themselves.