Endocrinology Flashcards
What gland produces parathyroid hormone (PTH)?
The parathyroid glands.
What is the main function of PTH in calcium regulation?
To increase blood calcium levels.
How does PTH affect bones?
It stimulates osteoclasts to break down bone and release calcium into the blood.
What effect does PTH have on the kidneys?
It increases calcium reabsorption and decreases phosphate reabsorption.
How does PTH indirectly affect the intestines?
It stimulates the activation of vitamin D, which increases intestinal calcium absorption.
What triggers the release of PTH?
Low blood calcium levels (hypocalcemia).
How does PTH affect phosphate levels in blood?
It lowers phosphate by promoting renal excretion.
What gland produces calcitonin?
The thyroid gland (parafollicular or C cells).
What is the primary function of calcitonin?
To lower blood calcium levels.
How does calcitonin act on bones?
It inhibits osteoclast activity, reducing bone resorption.
What is calcitonin’s effect on the kidneys?
It increases calcium excretion in the urine.
What stimulates calcitonin release?
High blood calcium levels (hypercalcemia).
Is calcitonin essential for calcium homeostasis in adults?
No, its role is minor compared to PTH and vitamin D.
What is the active form of vitamin D?
Calcitriol (1,25-dihydroxyvitamin D₃).
How is vitamin D activated?
Through hydroxylation in the liver and kidney, with PTH stimulating the kidney step.
What is the main role of vitamin D in calcium regulation?
To increase calcium and phosphate absorption from the intestines.
How does vitamin D affect bone?
It promotes mineralization by increasing calcium and phosphate availability.
How does vitamin D influence the kidneys?
It promotes reabsorption of calcium and phosphate.
What stimulates production of calcitriol in the kidney?
PTH and low phosphate levels.
What are dietary sources of vitamin D?
Fatty fish, fortified foods, and exposure to sunlight (UVB for skin synthesis).
