The Thyroid Hormones Flashcards
What does the hypothalamus recognise as a signal to start the production of TRH?
The signal is a drop in temperature
What converts T4 to the T3 ligand?
5-monodeiodooxidase (5-MD)
What are the 3 actions of hormones in utero and in children?
- Lung maturation in utereo
- Bone maturation
- Neonatal brain development
What are 5 other actions of the thyroid hormones?
- Increase basal metabolic rate
- Increased B-adreonceptor production to increase heart rate
- Skeletal muscle contractility
- Cardiac muscle contracility to increase heart rate
How do they thyroid hormones increase basal metabolic rate?
Increase Na+/K+ pump action, lipolysis and glycogenolysis
What is parathyroid hormone?
A hormone secreted by the chief cells in the parathyroid gland the regulates Ca2+ levels
How are low Ca2+ levels detected?
By receptors on the parathyroid chief cells
What does the parathyroid hormone do to raise the Ca2+ level?
It increases osteoclastic activity
Why would an increase in osteoclast activity increase Ca2+ levels?
Osteoclast reabsrob bone and produce calcium phosphate which increase plasma Ca2+ levels
Why is osteoclast activity downregulated after ca2+ levels have been restored?
Because phosphate loss inhibit bicarbonate
What is calcitonin?
A hormone that decreases calcium levels
Where is calcitonin secreted from?
The parafollicular cells of the thyroid
Does an increase is Ca2+ levels cause the release of calcitonin?
It is detected by receptors on the parafollicular cells which then secrete calcitonin
How does calcitonin decrease Ca2+ levels?
It decreases osteoclast activity which means bone reasborption is inhibited
