Q: Which equation best represents the relationship between calcium homeostasis and PTH release?

$$\text{If } [Ca$$^{2+}$$]_{blood} \downarrow \Rightarrow \text{PTH release} \uparrow$$

Question 1

Which hormone is primarily responsible for regulating blood calcium levels, and which cells secrete it?

Accepted Answer

Parathyroid hormone (PTH), secreted by parathyroid cells

Question 2

What is the effect of parathyroid hormone (PTH) on osteoclasts in bone tissue?

Accepted Answer

PTH stimulates osteoclasts to digest the calcium-rich bony matrix, releasing calcium and phosphate into the blood

Question 3

Which of the following is NOT a target organ of parathyroid hormone (PTH)?

Accepted Answer

Liver

Question 4

A patient presents with spontaneous bone fractures and kidney stones. Which endocrine disorder is most likely responsible?

Accepted Answer

Hyperparathyroidism

Question 5

What is the consequence of hypoparathyroidism on neuronal excitability?

Accepted Answer

Neurons become more excitable, causing tetany and convulsions

Question 6

Which process is enhanced by PTH in the kidneys to increase blood calcium levels?

Accepted Answer

Reabsorption of calcium from forming urine into the blood

Question 7

PTH promotes the activation of vitamin D in the kidneys. What is the active form of vitamin D called?

Accepted Answer

Calcitriol

Question 8

Which equation best represents the relationship between calcium homeostasis and PTH release?

Accepted Answer

$$	ext{If } [Ca$$^{2+}$$]_{blood} \downarrow \Rightarrow 	ext{PTH release} \uparrow$$

Question 9

Which of the following symptoms is most likely to occur in a patient with untreated hypoparathyroidism?

Accepted Answer

Respiratory paralysis and death

Question 10

A patient has low blood calcium levels. Which sequence of events is most likely to occur?

Accepted Answer

PTH release increases, stimulating osteoclasts, kidney reabsorption of calcium, and activation of vitamin D

Question 11

Which of the following best describes the role of vitamin D in calcium absorption?

Accepted Answer

Vitamin D is required for absorption of calcium from food, but must be activated by the kidneys

Question 12

Which of the following is a plausible outcome of hypercalcemia caused by hyperparathyroidism?

Accepted Answer

Depressed nervous system and weak skeletal muscles

Question 13

Which cells in the parathyroid gland secrete parathyroid hormone?

Accepted Answer

Parathyroid cells

Question 14

Which of the following best explains why precise control of blood calcium levels is critical?

Accepted Answer

Calcium homeostasis is essential for nerve transmission, muscle contraction, and blood clotting

Question 15

Which of the following is a multi-step effect of PTH on blood calcium levels?

Accepted Answer

PTH stimulates osteoclasts, enhances kidney reabsorption of calcium, and promotes activation of vitamin D, leading to increased calcium absorption in the intestine

Question 16

Which clinical sign is most likely to be observed in a patient with osteitis fibrosa cystica?

Accepted Answer

Moth-eaten appearance of bones on X-rays and spontaneous fractures

Question 17

Which equation represents the effect of PTH on calcium reabsorption in the kidneys?

Accepted Answer

$$	ext{PTH} ightarrow 	ext{Kidney reabsorption of } Ca$$^{2+}$$ \uparrow$$

Question 18

Which of the following is a plausible reason for the formation of kidney stones in hyperparathyroidism?

Accepted Answer

Excess calcium salts precipitate in kidney tubules due to elevated blood calcium levels

Question 19

Which of the following best describes the feedback mechanism controlling PTH release?

Accepted Answer

Negative feedback: Rising blood calcium levels inhibit PTH release

Question 20

Which of the following is a likely outcome if the parathyroid glands are accidentally removed during thyroid surgery?

Accepted Answer

Hypoparathyroidism leading to hypocalcemia, tetany, and convulsions

The Parathyroid Glands and Calcium Homeostasis

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