Endocrine System Overview Practice Tests

Question 1

The concentration of a hormone in the blood is found to decrease by 50% every 30 minutes. If the initial concentration of the hormone is 100 ng/mL, what will the concentration be after 1.5 hours, assuming first-order kinetics?

Accepted Answer

12.5 ng/mL

Answer

50 ng/mL

Answer

25 ng/mL

Answer

6.25 ng/mL

Question 2

A patient presents with symptoms of hypercalcemia. Based on your understanding of humoral stimuli, which hormone is most likely being overproduced, and what is the expected effect on blood phosphate levels? Explain the relationship using MathJax notation for relevant chemical species.

Accepted Answer

Parathyroid hormone (PTH) is likely overproduced. PTH increases blood calcium levels ($Ca^{2+}$) and decreases blood phosphate levels ($PO_4^{3-}$). PTH stimulates osteoclasts to release calcium and phosphate from bone, increases calcium reabsorption in the kidneys, and enhances phosphate excretion. It also indirectly increases calcium absorption in the intestines by activating vitamin D.

Question 3

A researcher is studying the effect of a new drug on hormone receptor binding affinity. They find that the drug increases the number of receptors on the target cells. This phenomenon is best described as:

Accepted Answer

Up-regulation

Answer

Down-regulation

Answer

Permissiveness

Answer

Synergism

Question 4

Steroid hormones typically bind to plasma membrane receptors and activate second-messenger systems to exert their effects on target cells.

Accepted Answer

True

Answer

False

Question 5

Which of the following are examples of amino acid-based hormones?

Answer

Aldosterone

Answer

Epinephrine

Answer

Insulin

Answer

Thyroxine

Question 6

Two hormones, glucagon and cortisol, both increase blood glucose levels. If the effect of glucagon alone increases blood glucose by 2 mmol/L and the effect of cortisol alone increases it by 1 mmol/L, but when both are present, blood glucose increases by 4 mmol/L, what type of hormonal interaction is likely occurring? Explain your answer.

Accepted Answer

Synergism. Synergism occurs when the combined effect of two hormones is greater than the sum of their individual effects. In this case, 2 mmol/L + 1 mmol/L = 3 mmol/L, but the actual increase is 4 mmol/L, indicating a synergistic effect.

Question 7

The concentration of a hormone is determined to follow the equation $C(t) = C_0 e^{-kt}$, where $C_0$ is the initial concentration, $k = 0.02 	ext{ min}^{-1}$ is the decay constant, and $t$ is time in minutes. If the initial concentration of ADH is $5 	ext{ pg/mL}$, what is the concentration after 30 minutes?

Accepted Answer

B. 2.74 pg/mL

Answer

A. 1.23 pg/mL

Answer

C. 3.45 pg/mL

Answer

D. 4.12 pg/mL

Question 8

The rate of thyroid hormone (TH) production is governed by the equation $R = k \cdot TSH$, where $R$ is the rate of TH production in $\mu g/hr$, $k = 2.5 \mu g/hr$ per $mU/L$, and $TSH$ is the thyroid-stimulating hormone concentration in $mU/L$. If the normal range of TSH is $0.4 - 4.0 	ext{ mU/L}$, what is the range of TH production rates?

Accepted Answer

C. 1.0 - 10.0 \mu g/hr

Answer

A. 0.1 - 1.0 \mu g/hr

Answer

B. 0.4 - 4.0 \mu g/hr

Answer

D. 2.5 - 25.0 \mu g/hr

Question 9

The half-life of parathyroid hormone (PTH) in the bloodstream is approximately 4 minutes. If the initial concentration of PTH is $100 	ext{ pg/mL}$, what will the concentration be after 12 minutes, assuming first-order kinetics?

Accepted Answer

12.5 pg/mL

Question 10

The hypothalamic-hypophyseal portal system directly connects the posterior pituitary to the hypothalamus, allowing for rapid transport of releasing and inhibiting hormones.

Accepted Answer

True

Answer

False

Question 11

Which of the following hormones are directly regulated by the hypothalamus via releasing or inhibiting hormones?

Answer

A. Growth Hormone (GH)

Answer

B. Thyroid-Stimulating Hormone (TSH)

Answer

C. Adrenocorticotropic Hormone (ACTH)

Answer

D. Follicle-Stimulating Hormone (FSH)

Answer

E. Luteinizing Hormone (LH)

Answer

F. Prolactin (PRL)

Answer

G. Oxytocin

Answer

H. Antidiuretic Hormone (ADH)

Question 12

If the rate of calcium absorption in the intestines is given by $A = k \cdot [Vitamin D]$, where $A$ is the absorption rate, $k = 5 	ext{ mg/day per } 	ext{IU/mL}$, and $[Vitamin D]$ is the concentration of activated vitamin D in $	ext{IU/mL}$, and PTH increases activated Vitamin D concentration from $0.1 	ext{ IU/mL}$ to $0.5 	ext{ IU/mL}$, what is the increase in calcium absorption rate?

Accepted Answer

B. 2.0 mg/day

Answer

A. 0.5 mg/day

Answer

C. 2.5 mg/day

Answer

D. 5.0 mg/day

Question 13

A patient has a TSH level of 0.1 mU/L and a free T4 level of 25 pmol/L. Given that the normal TSH range is 0.4-4.0 mU/L and the normal free T4 range is 9-25 pmol/L, what thyroid condition might this patient have?

Accepted Answer

Hyperthyroidism

Question 14

A patient presents with hypertension, edema, and abnormal neuron and muscle function. Lab results show elevated levels of aldosterone. Which of the following mechanisms is most likely contributing to these symptoms, given that $R$ represents the rate of aldosterone secretion and $[Na^+]$ and $[K^+]$ represent the plasma concentrations of sodium and potassium, respectively?

Accepted Answer

A. Adrenal tumor leading to hypersecretion of aldosterone, where $R \propto [Na^+]$ and $R \propto \frac{1}{[K^+]}$.

Answer

B. Decreased ACTH secretion, where $R \propto ACTH$ and reduced aldosterone leads to sodium retention.

Answer

C. Increased ANP secretion, where $R \propto \frac{1}{ANP}$ and aldosterone secretion is stimulated.

Answer

D. Renin deficiency, where $R \propto Renin$ and aldosterone secretion is stimulated.

Question 15

A researcher is studying the effect of a new drug on cortisol secretion. The drug inhibits the enzyme 11β-HSD1, which converts cortisone to cortisol in peripheral tissues. If the baseline cortisol level is $C_0$ and the drug reduces the conversion rate by 30%, what is the expected cortisol level $C_1$ after the drug takes effect, assuming no compensatory mechanisms?

Accepted Answer

0.7 $C_0$

Question 16

Which of the following physiological responses are directly stimulated by the release of epinephrine from the adrenal medulla? Select all that apply.

Answer

A. Increased heart rate

Answer

B. Bronchial dilation

Answer

C. Increased blood glucose levels

Answer

D. Decreased blood pressure

Answer

E. Increased insulin secretion

Question 17

Glucagon promotes glycogenolysis and gluconeogenesis in the liver, leading to a decrease in blood glucose levels. True or False?

Accepted Answer

False

Answer

True

Question 18

A patient with diabetes mellitus has a blood glucose level of 250 mg/dL. If the normal range is 70-100 mg/dL, by what percentage does the patient's blood glucose level exceed the upper limit of the normal range, given that $G$ is the glucose level?

Accepted Answer

C. 150%

Answer

A. 50%

Answer

B. 100%

Answer

D. 250%

Question 19

The production of erythropoietin by the kidneys is regulated by a negative feedback loop involving oxygen levels in the blood. Assuming a patient's arterial blood oxygen partial pressure ($P_{a}O_2$) drops from a normal value of 95 mmHg to 60 mmHg, and the normal erythropoietin production rate is 10 units/day, estimate the percentage increase in erythropoietin production rate if the production rate is inversely proportional to the square of the $P_{a}O_2$.

Accepted Answer

Approximately 151.39%

Question 20

Which of the following hormones is NOT primarily involved in regulating blood pressure or blood volume?

Accepted Answer

D. Leptin

Answer

A. Atrial natriuretic peptide (ANP)

Answer

B. Renin

Answer

C. Aldosterone

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