Endocrine Flashcards
(47 cards)
What 3 hormones does the thyroid gland produce?
- Thyroxine (T4)
- Triiodothyronine (T3)
- Calcitonin
What enzyme converts T4 –> T3?
Deiodinase
Are T3 or T4 levels higher in the blood?
T4 (store of T3)
Describe thyroid hormone synthesis (7)
- TSH binds to TSHR
- Na+/I- symporter transports I- into follicular cells
- Iodination of thyroglobulin via thyroperoxidase enzyme
- Iodinated tyrosines on thyroglobulin combine via thyroperoxidase enzyme
- Mature thyroglobulin stored in colloid
- Colloid absorbed into follicular cells via endocytosis
- Hydrolytic enzymes in lysosomes liberate T3 & T4
What are the actions of thyroid hormone?
- Increases metabolic rate (more energy produced, heat produced)
- Increases catecholamine effect (adrenaline)
- Growth & development
Is T3 or T4 more active?
T3
Describe the process of thyroid hormone secretion
- HT: increases TRH secretion
- AP: increases TSH secretion
- TG: increases thyroid secretion
- Increased plasma thyroid hormone has a negative feedback on the AP (and the HT)
What stimulates parathyroid hormone secretion?
- Low serum Ca2+
- High serum phosphate
What are the actions of PTH? (4)
- Increase Ca2+ absorption (in intestines)
- Increase Ca2+ reabsorption from DCT (via activation of vit D)
- Increase Ca2+ release (resorption) from bone
- Decrease phosphate reabsorption in kidneys
Define endocrine
Hormones released into the blood, acting at distant sites
Define paracrine
Hormones acting on adjacent cells
Define autocrine
Hormones acting on the same cell that secreted it
What hormone regulates GH and how? (2)
GHRH +
SST (somatostatin) -
What hormone regulates TSH and how?
TRH +
What hormone regulates Prolactin (PLN)?
Dopamine -
What hormone regulates ACTH?
CRH +
What hormone regulates FSH and LH?
GnRH +
How is prolactin different from the other anterior pituitary hormones?
Prolactin is under inhibitory control by dopamine.
Stopping the inhibition will cause prolactin levels to increase
What are the anterior pituitary hormones? (5)
FSH & LH GH ACTH TSH PLN
What does GH do? (3)
Stimulates.liver to secrete IGF-1
Lipid + carb metabolism
Protein synthesis
What does TSH do?
Stimulates release fo T3 & T4 from thyroid gland
What does prolactin do? (2)
Stimulates breast development
Milk production
What does ACTH do?
Stimulates cortisol release from adrenal cortex
What do FSH and LH do? (2)
Germ cell (ovum + sperm) development Stimulate sex hormone secretion (testesterone, progesterone)