7.6 Flashcards
Describe a histological cross section of the thyroid
- Follicular cells arranged in spheres, each containing a lumen that acts as a storage site for thyroid hormone
- C cells secrete calcitonin
- Capillaries
How is thyroid hormone secretion regulated?
Negative feedback on T3 and T4 by TSH and TRH
What non-genomic effects of TSH allow T3 and T4 to be secreted?
- Proteolysis of thyroglobulin (releasing more T3/T4)
- Increases iodination of tyrosine (more T3 and T4 synthesis)
- Increases iodine pump activity (more iodine for iodination)
What genomic effects of TSH allow increased T3/T4 synthesis?
- More synthesis of iodine pump, thyroglobulin
- Hypertrophy/hyperplasia of gland
Effects of thyroid hormone on oxygen delivery
- HR increase
- Resting resp rate increase
- RBC mass increase
Effect of thyorid hormone on neural activity
- Alertness increase
- Memory increase
- Emotional stability increase
Effect of thyroid hormone on metabolism
- Increase mitochondrial activity, increased basal metabolic rate
- Increased heat production
- Increased lypolysis and glycogenolysis
Effect of T3 and T4 on reproduction and growth
- Required for reproductive capabilities
- Enhances growth hormone
Provide an example of hypothyroidism
Hashimoto’s disease (primary hypothyroidism): autoantibodies against thyroglobulin`
Provide an example of hyperthyroidism
Graves’ disease; Thyroid-stimulating Immunoglobulin causes overstimulation of thyroid
Which three hormones are responsible for plasma calcium concentration regulation?
- Calcitonin
- Calcitriol
- PTH
How is vitamin D activated by PTH?
Increases activity of enzyme that converts vitamin D precursor into calcitriol, allowing increased intestinal absorption.
What is the action of calcitonin?
Decreases calcium reabsorption, inhibiting osteoclasts and decreasing kidney absorption of Ca2+
