5 Questions
Which of the following thyroid hormones is produced from thyroid follicles?
3, 5, 3' triiodothyronine (T3)
What is the primary function of calcitonin?
Reducing blood calcium levels
Which thyroid hormone is biologically inactive?
3,3',5' triiodothyronine (rT3)
What is the number of amino acids in the calcitonin peptide hormone?
32 amino acids
Where are calcitonin-producing cells located in the thyroid gland?
Parafollicular cells (C cells)
Study Notes
Thyroid Hormones
- The thyroid gland produces two main hormones from thyroid follicles: thyroxine (T4) and triiodothyronine (T3), with the chemical structure of 3, 5, 3', 5' tetraiodothyronine and 3, 5, 3' triiodothyronine, respectively.
- The thyroid gland also secretes small amounts of biologically inactive reverse T3 (rT3), with a chemical structure of 3,3',5' triiodothyronine.
Calcitonin
- Calcitonin is a 32-amino acid peptide hormone secreted by parafollicular cells (C cells) of the thyroid.
- Calcitonin reduces blood calcium levels through three mechanisms:
- Inhibiting osteoclast activity
- Inhibiting renal tubular reabsorption of calcium
- Inhibiting intestinal absorption of calcium
Learn about the thyroid hormones, including thyroxine and triiodothyronine, and the hormone calcitonin produced by the parafollicular cells.
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