Q: Which equation best represents the negative feedback loop regulating thyroid hormone levels?

$$\text{Low } T_3$/T_4$ \rightarrow \text{Hypothalamus} \xrightarrow{TRH} \text{Anterior Pituitary} \xrightarrow{TSH} \text{Thyroid} \xrightarrow{T_3$/T_4$} \text{Target Cells}$$

Question 1

Which of the following best describes the role of the thyroid gland in metabolism?

Accepted Answer

It controls metabolism by producing T3 and T4 hormones.

Question 2

What is the primary function of parafollicular cells in the thyroid gland?

Accepted Answer

Secretion of calcitonin to lower blood calcium levels.

Question 3

Which of the following is a correct step in the synthesis of thyroid hormones?

Accepted Answer

Iodine is absorbed by follicular epithelial cells and added to thyroglobulin.

Question 4

Why are T3 and T4 considered unique among amino acid-based hormones?

Accepted Answer

They are lipid soluble and travel in blood bound to carriers.

Question 5

Which equation best represents the negative feedback loop regulating thyroid hormone levels?

Accepted Answer

$$	ext{Low } T_3$/T_4$ ightarrow 	ext{Hypothalamus} \xrightarrow{TRH} 	ext{Anterior Pituitary} \xrightarrow{TSH} 	ext{Thyroid} \xrightarrow{T_3$/T_4$} 	ext{Target Cells}$$

Question 6

A patient presents with unexplained weight loss, sweating, and rapid heartbeat. Blood work shows high T4 and low TSH. What is the most likely diagnosis?

Accepted Answer

Hyperthyroidism

Question 7

Which hormone is secreted by the parathyroid gland and what is its primary function?

Accepted Answer

Parathyroid hormone (PTH); increases blood calcium levels

Question 8

How does parathyroid hormone (PTH) increase blood calcium levels? Select the most complete answer.

Accepted Answer

By increasing calcium reabsorption in kidneys and activating vitamin D for increased intestinal absorption.

Question 9

Which layer of the adrenal cortex is responsible for producing mineralocorticoids, and what is the main mineralocorticoid?

Accepted Answer

Zona glomerulosa; aldosterone

Question 10

Aldosterone increases blood pressure by which of the following mechanisms?

Accepted Answer

Stimulating Na+/K+ pumps in the kidney to increase Na+ reabsorption and K+ secretion.

Question 11

Which of the following is NOT a regulatory mechanism for aldosterone secretion?

Accepted Answer

Thyroid stimulating hormone (TSH)

Question 12

A patient with an adrenal tumor presents with hypertension and edema. Lab results show excess Na+ retention and K+ loss. What is the most likely diagnosis?

Accepted Answer

Aldosteronism

Question 13

Which hormone is the primary glucocorticoid produced by the adrenal cortex, and what is its main function?

Accepted Answer

Cortisol; regulates metabolism and stress response

Question 14

What is the correct sequence for the regulation of cortisol secretion?

Accepted Answer

$$	ext{CRH from hypothalamus} ightarrow 	ext{ACTH from anterior pituitary} ightarrow 	ext{Cortisol from adrenal cortex}$$

Question 15

Which of the following is a physiological effect of excess cortisol?

Accepted Answer

Depressed immune system and cartilage formation

Question 16

A patient presents with skin bronzing and severe fatigue. Lab results show low cortisol. What is the most likely diagnosis?

Accepted Answer

Addison's disease

Question 17

Which hormone is released by the adrenal medulla and what is its primary effect during stress?

Accepted Answer

Epinephrine; increases heart rate and redirects blood to essential organs

Question 18

Which of the following is NOT an effect of catecholamines released by the adrenal medulla?

Accepted Answer

Increases gut motility

Question 19

Which adrenal cortex hormone is a minor contributor to secondary sex characteristics and is the primary source of estrogen in post-menopausal women?

Accepted Answer

Gonadocorticoids (e.g., androstenedione, DHEA)

Endocrine System Part II: Thyroid, Parathyroid, and Adrenal Glands

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