Endocrinology Practice Questions

Q: What is the primary mechanism through which catecholamines stabilize blood glucose concentration in response to hypoglycemia?

Catecholamines stimulate gluconeogenesis in the liver.. **Explanation:** The primary goal of catecholamines (Epinephrine and Norepinephrine) during hypoglycemia is to increase blood glucose levels rapidly. This is achieved through the activation of **$\beta_2$ and $\alpha_1$ receptors** in the liver. **Why Option D is correct:** Catecholamines are potent counter-regulatory hormones. They stimulate **gluconeogenesis** (the synthesis of glucose from non-carbohydrate precursors like lactate and amino acids) and **glycogenolysis** (breakdown of glycogen) in the liver. By increasing the expression of key enzymes like PEPCK (Phosphoenolpyruvate carboxykinase), they ensure a sustained release of glucose into the systemic circulation to protect the brain. **Why other options are incorrect:** * **Option A:** While catecholamines do stimulate glycogen phosphorylase in muscles, **muscle lacks the enzyme Glucose-6-Phosphatase**. Therefore, muscle glycogen is converted to lactate (via glycolysis) rather than free glucose, and cannot directly contribute to blood glucose levels. * **Option B:** Catecholamines **stimulate** liver glycogenolysis; inhibiting it would worsen hypoglycemia. * **Option C:** Catecholamines actually **inhibit insulin release** (via $\alpha_2$ receptors) and stimulate glucagon release (via $\beta_2$ receptors) to prevent further glucose uptake by peripheral tissues. **High-Yield NEET-PG Pearls:** * **Dual Action:** Catecholamines increase glucose **production** (liver) and decrease glucose **utilization** (peripheral tissues like muscle/adipose) to spare glucose for the CNS. * **Receptor Specificity:** Hepatic glucose production is mediated by both $\alpha_1$ and $\beta_2$ receptors, but the **inhibition of insulin** is primarily an **$\alpha_2$ effect**. * **Hierarchy:** In the defense against hypoglycemia, Glucagon is the first line of defense, followed closely by Epinephrine. Cortisol and Growth Hormone act much later.

Q: Basal metabolic rate (BMR) depends on which of the following factors?

Amount of lean body mass. **Explanation:** The **Basal Metabolic Rate (BMR)** is the minimum amount of energy required to maintain vital functions (like breathing and circulation) at complete physical and mental rest. **Why Lean Body Mass (LBM) is the correct answer:** The primary determinant of BMR is the amount of **metabolically active tissue** in the body. Lean body mass—which includes skeletal muscle, organs (liver, brain, kidneys), and bone—is highly active and consumes significantly more oxygen and energy than fat. Skeletal muscle alone accounts for a large portion of the BMR; therefore, individuals with higher LBM (e.g., athletes or males) have a higher BMR. **Analysis of Incorrect Options:** * **Body Weight:** While BMR generally increases with weight, total weight is a poor predictor because it does not differentiate between fat and muscle. Two people of the same weight can have vastly different BMRs based on their body composition. * **Body Surface Area (BSA):** Historically, BMR was expressed per square meter of BSA (the "Surface Law"). While heat loss is proportional to surface area, BSA is a *proxy* measurement rather than the underlying physiological driver. LBM remains the most accurate biological determinant. * **Adipose Tissue:** Fat is metabolically sluggish. An increase in adipose tissue (obesity) actually leads to a **decrease** in BMR relative to total body weight. **High-Yield Clinical Pearls for NEET-PG:** * **Thyroid Status:** Thyroid hormones ($T_3$ and $T_4$) are the most important hormonal regulators of BMR. * **Specific Dynamic Action (SDA):** Protein has the highest SDA (30%), meaning it increases metabolic rate the most during digestion. * **Gender & Age:** BMR is higher in males (due to more LBM) and decreases with age (due to sarcopenia/loss of muscle). * **Starvation:** BMR decreases during prolonged fasting as a compensatory mechanism to conserve energy.

Q: Thyroid gland function is best monitored by which of the following?

Level of thyroid stimulating hormone. **Explanation:** The **Serum TSH (Thyroid Stimulating Hormone)** level is considered the most sensitive and specific single test for monitoring thyroid function and screening for thyroid disorders. This is due to the **negative feedback loop** between the pituitary and the thyroid gland. Even minor changes in the levels of free T4 and T3 trigger a logarithmic change in TSH secretion. Therefore, TSH can detect subclinical thyroid dysfunction even when T3 and T4 levels are within the normal reference range. **Analysis of Incorrect Options:** * **Basal Metabolic Rate (BMR):** Historically used, but it is highly non-specific and influenced by numerous factors like anxiety, fever, and drugs. It is no longer used for primary monitoring. * **Thyroxine and Tri-iodothyronine uptake:** These tests measure the binding capacity of thyroid-binding globulin (TBG). While useful in specific contexts (like calculating the Free Thyroxine Index), they do not directly reflect the functional status of the thyroid as accurately as TSH. * **Protein Bound Iodine (PBI):** This is an obsolete test. It measures the total iodine in the blood, which includes both hormonal and non-hormonal iodine, making it unreliable due to interference from dietary iodine or contrast agents. **Clinical Pearls for NEET-PG:** * **Best Screening Test:** Serum TSH. * **Best test for monitoring Levothyroxine replacement:** Serum TSH (target range 0.5–2.5 mIU/L). * **Exception:** In **Secondary (Central) Hypothyroidism**, TSH is unreliable; monitoring must be done using **Free T4** levels. * **Subclinical Hypothyroidism:** Elevated TSH with normal Free T4.

Q: Which of the following directly inhibits insulin secretion?

Alpha2-adrenergic agonist. **Explanation:** The secretion of insulin by pancreatic beta cells is tightly regulated by the autonomic nervous system and various hormones. **1. Why Alpha2-adrenergic agonists are correct:** The sympathetic nervous system has a dual effect on insulin secretion, but the **inhibitory effect mediated by $\alpha_2$-adrenergic receptors** is dominant. When $\alpha_2$ receptors are stimulated (via norepinephrine or agonists), they couple with $G_i$ proteins, leading to a decrease in intracellular cAMP levels. This inhibits the exocytosis of insulin granules. This mechanism is physiologically vital during exercise or stress (the "fight or flight" response) to prevent hypoglycemia while ensuring adequate glucose is available for the brain and muscles. **2. Why the other options are incorrect:** * **B. Beta2-adrenergic agonist:** Stimulation of $\beta_2$ receptors (via $G_s$ proteins) actually **increases** insulin secretion. However, in a systemic sympathetic discharge, the $\alpha_2$ inhibitory effect overrides the $\beta_2$ stimulatory effect. * **C. Cholecystokinin (CCK):** This is a gastrointestinal hormone (incretin-like effect) that **stimulates** insulin secretion in response to food intake. * **D. Glucagon:** Glucagon has a direct paracrine effect on adjacent beta cells to **stimulate** insulin secretion, ensuring that the glucose released by the liver (via glycogenolysis) can be utilized by peripheral tissues. **High-Yield Clinical Pearls for NEET-PG:** * **Dominant Control:** While Parasympathetic (Vagus/M3) and $\beta_2$ stimulation increase insulin, **$\alpha_2$ stimulation is the most potent physiological inhibitor.** * **Somatostatin:** Produced by Delta ($\delta$) cells, it is a potent paracrine inhibitor of both insulin and glucagon. * **Incretin Effect:** Oral glucose causes a much higher insulin spike than IV glucose due to hormones like GLP-1 and GIP.

Q: Which of the following is NOT produced by the ovary?

Gonadotropin. ### Explanation **1. Why Gonadotropin is the Correct Answer:** Gonadotropins, specifically **Follicle-Stimulating Hormone (FSH)** and **Luteinizing Hormone (LH)**, are peptide hormones synthesized and secreted by the **gonadotroph cells of the anterior pituitary gland**. Their primary role is to stimulate the ovaries (and testes) to produce sex steroids and gametes. Since they are the *stimulators* of the ovary rather than products *of* the ovary, they are the correct answer. **2. Why the Other Options are Incorrect:** * **Estrogen:** This is the primary female sex hormone produced by the **granulosa cells** of the ovarian follicles (via the aromatization of androgens). * **Testosterone:** While often considered a male hormone, the ovary (specifically the **theca cells**) produces androgens like androstenedione and testosterone. Most of this is converted to estrogen, but some is secreted into the systemic circulation. * **Inhibin B:** This is a glycoprotein hormone secreted by the **granulosa cells** of the developing follicles. It provides negative feedback to the anterior pituitary to specifically inhibit FSH secretion. **3. High-Yield Clinical Pearls for NEET-PG:** * **Two-Cell, Two-Gonadotropin Theory:** LH stimulates **Theca cells** to produce androgens (Cholesterol → Androstenedione); FSH stimulates **Granulosa cells** to convert those androgens into Estrogen (via Aromatase). * **Inhibin Markers:** **Inhibin B** is a marker of follicular reserve (produced by small antral follicles), while **Inhibin A** is produced by the corpus luteum. * **Human Chorionic Gonadotropin (hCG):** Although it is a gonadotropin, it is produced by the **syncytiotrophoblast** of the placenta, not the ovary.

Q: Which of the following hormones increases with age?

Luteinizing Hormone (LH). **Explanation:** The correct answer is **Luteinizing Hormone (LH)**. This phenomenon is primarily driven by the age-related decline in gonadal function, known as the "somatopause" in men and menopause in women. **1. Why LH increases:** As individuals age, there is a progressive decrease in the production of sex steroids (Estrogen/Progesterone in females and Testosterone in males) due to primary gonadal failure. This loss of negative feedback on the hypothalamic-pituitary-gonadal (HPG) axis leads to a compensatory increase in the secretion of **Gonadotropins**, specifically **LH and FSH**. In post-menopausal women, FSH typically rises more significantly than LH, but both remain elevated compared to reproductive years. **2. Why other options are incorrect:** * **Growth Hormone (GH):** GH secretion declines significantly with age (approximately 14% per decade after age 30), contributing to reduced muscle mass and increased adiposity. * **Prolactin:** Levels generally remain stable or slightly decrease with age, particularly in post-menopausal women due to the lack of estrogenic stimulation on lactotrophs. * **Insulin:** While insulin *resistance* often increases with age, the actual basal secretion of insulin tends to decline due to progressive $\beta$-cell dysfunction and reduced pancreatic mass. **High-Yield Clinical Pearls for NEET-PG:** * **Hormones that Decrease with Age:** GH, Melatonin, DHEA (Dehydroepiandrosterone), Aldosterone, and Testosterone. * **Hormones that Increase with Age:** LH, FSH, PTH (Parathyroid Hormone), Norepinephrine, and Cortisol (slight increase in evening levels). * **Hormones that remain Unchanged:** Thyroid hormones (T3/T4) usually remain in the normal range, though TSH may show a slight upward shift in the elderly.

Question 1

Testosterone is produced in Leydig cells in the fetus due to which of the following?

Accepted Answer

ssHCG

Answer

FSH

Answer

Cortisol

Answer

Estrogen

Question 2

Virilization of the female is present in all of the following conditions EXCEPT?

Accepted Answer

17-α hydroxylase deficiency

Answer

21-α hydroxylase deficiency

Answer

11-α hydroxylase deficiency

Answer

11-β hydroxysteroid deficiency

Question 3

What is the primary mechanism through which catecholamines stabilize blood glucose concentration in response to hypoglycemia?

Accepted Answer

Catecholamines stimulate gluconeogenesis in the liver.

Answer

Catecholamines stimulate glycogen phosphorylase to release glucose from muscle.

Answer

Catecholamines inhibit glycogenolysis in the liver.

Answer

Catecholamines stimulate the release of insulin from the pancreas.

Question 4

Which of the following most accurately describes the transmembrane signaling process involved in steroid hormone action?

Accepted Answer

Diffusion across the membrane and binding to an intracellular receptor

Answer

Action on a membrane-spanning tyrosine kinase

Answer

Action of a G protein, which activates or inhibits adenylyl cyclase

Answer

Opening of transmembrane ion channels

Question 5

What happens when the availability of oxygen to tissues decreases?

Accepted Answer

Vasodilation and increase in blood supply to the tissue takes place.

Answer

Vasoconstriction and decrease in blood supply to the tissue takes place.

Answer

Venoconstriction and increase in tissue perfusion pressure occurs.

Answer

Venodilation and decrease in tissue perfusion pressure occurs.

Question 6

Basal metabolic rate (BMR) depends on which of the following factors?

Accepted Answer

Amount of lean body mass

Answer

Body weight

Answer

Body surface area

Answer

Amount of adipose tissue

Question 7

Thyroid gland function is best monitored by which of the following?

Accepted Answer

Level of thyroid stimulating hormone

Answer

Basal metabolic rate (BMR)

Answer

Thyroxine and tri-iodothyronine uptake

Answer

Level of protein bound iodine

Question 8

Which of the following directly inhibits insulin secretion?

Accepted Answer

Alpha2-adrenergic agonist

Answer

Beta2-adrenergic agonist

Answer

Cholecystokinin

Answer

Glucagon

Question 9

Which of the following is NOT produced by the ovary?

Accepted Answer

Gonadotropin

Answer

Testosterone

Answer

Estrogen

Answer

Inhibin B

Question 10

Which of the following hormones increases with age?

Accepted Answer

Luteinizing Hormone (LH)

Answer

Growth Hormone (GH)

Answer

Prolactin

Answer

Insulin

Endocrinology — MCQs

Endocrinology — MCQs

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