Endocrinology Practice Questions

Q: Growth hormone increases all of the following except?

Metabolism of carbohydrates. **Explanation:** Growth Hormone (GH) is primarily an anabolic hormone regarding proteins, but it acts as a **"Diabetogenic"** and **"Glucose-sparing"** hormone regarding fuel metabolism. **Why "Metabolism of carbohydrates" is the correct answer:** GH actually **decreases** the peripheral utilization (metabolism) of carbohydrates. It induces insulin resistance by inhibiting the uptake of glucose by skeletal muscle and adipose tissue. By sparing glucose, the body shifts its energy source from carbohydrates to fats. Therefore, saying GH "increases" carbohydrate metabolism is physiologically incorrect. **Analysis of Incorrect Options:** * **A. Blood glucose concentration:** GH increases blood glucose by stimulating gluconeogenesis in the liver and reducing glucose uptake in peripheral tissues (Anti-insulin effect). * **B. Blood free fatty acid concentration:** GH is highly **lipolytic**. It activates hormone-sensitive lipase, breaking down triglycerides into free fatty acids (FFAs) to be used as the primary energy source. * **C. Protein synthesis:** GH is a potent anabolic agent. It increases amino acid transport into cells, enhances DNA transcription/translation, and decreases protein catabolism, leading to a positive nitrogen balance. **NEET-PG High-Yield Pearls:** * **Ketogenic Effect:** Due to excessive mobilization of FFAs, GH is considered ketogenic. * **IGF-1 (Somatomedin C):** Most growth-promoting effects of GH (bone and cartilage growth) are mediated via IGF-1, produced mainly in the liver. * **Pulsatile Secretion:** GH is secreted in pulses, with the largest spike occurring during **Deep Sleep (Stage N3)**. * **Stimuli:** Hypoglycemia, fasting, and exercise are potent stimulators of GH release.

Q: Insulin-like growth factor-II (IGF-II) is synthesized in all of the following tissues EXCEPT:

Cartilage. **Explanation:** The synthesis of Insulin-like Growth Factors (IGFs) is a critical component of the growth hormone (GH) axis. While **IGF-I** is primarily GH-dependent and synthesized in the liver and peripheral tissues like **cartilage** (where it acts locally via autocrine/paracrine mechanisms to promote bone growth), **IGF-II** follows a different physiological pattern. **Why Cartilage is the Correct Answer:** IGF-II is primarily a **fetal growth factor**. While it is synthesized in various adult tissues, it is notably **not synthesized in cartilage**. In contrast, cartilage is a major site for IGF-I synthesis, which mediates the longitudinal growth effects of Growth Hormone. **Analysis of Incorrect Options:** * **Liver (B):** The liver is the primary site of synthesis for both IGF-I and IGF-II in adults. IGF-II levels in the blood remain relatively high throughout adulthood, though its metabolic role is less dominant than IGF-I. * **Brain (A) and Pancreas (D):** IGF-II is widely expressed in several extrahepatic tissues. It is synthesized in the **brain** (where it plays a role in cognitive function and neurogenesis) and the **pancreas** (involved in beta-cell mass regulation). **High-Yield NEET-PG Pearls:** * **IGF-I (Somatomedin C):** Major mediator of postnatal growth; synthesis is GH-dependent. * **IGF-II:** Major mediator of fetal growth; synthesis is largely GH-independent. * **Receptors:** IGF-I acts via a tyrosine kinase receptor (similar to insulin). The IGF-II receptor is identical to the **Mannose-6-Phosphate receptor**, which is involved in lysosomal enzyme targeting. * **Clinical Correlation:** Excessive IGF-II production by non-islet cell tumors can lead to **hypoglycemia** (Doege-Potter Syndrome).

Q: Which of the following acts on nuclear receptors?

Thyroxine. **Explanation:** The mechanism of hormone action is determined by the chemical nature of the hormone. Receptors are generally classified into cell surface receptors (for water-soluble hormones) and intracellular receptors (for lipid-soluble hormones). **1. Why Thyroxine (B) is the Correct Answer:** Thyroid hormones (T3 and T4) are unique. Although they are derived from the amino acid tyrosine, they are lipophilic. They enter the cell via carrier-mediated transport and bind directly to **nuclear receptors** (specifically the Thyroid Hormone Receptor, TR). Once bound, they act as hormone-activated transcription factors, altering gene expression. **2. Analysis of Incorrect Options:** * **Glucocorticoids (A) and Progesterone (C):** These are steroid hormones. While they act on intracellular receptors, their primary receptors are located in the **cytoplasm**. Upon binding, the hormone-receptor complex translocates into the nucleus. Therefore, while they have nuclear effects, "Thyroxine" is the classic textbook answer for a receptor that is constitutively located *inside* the nucleus. * **Insulin (D):** This is a peptide hormone. It is water-soluble and cannot cross the lipid bilayer. It binds to a **transmembrane receptor** with intrinsic **Tyrosine Kinase** activity (Enzyme-linked receptor). **High-Yield NEET-PG Pearls:** * **Pure Nuclear Receptors:** Thyroid hormones (T3/T4), Retinoic acid (Vitamin A), and Vitamin D. * **Cytoplasmic Receptors:** Steroid hormones (Glucocorticoids, Mineralocorticoids, Progesterone, Estrogen, Testosterone). * **Mnemonic for Tyrosine Kinase:** "PIG" (Prolactin, Insulin, Growth Hormone). * **Note:** In many recent physiological classifications, both steroids and thyroid hormones are grouped as "Intracellular Receptors," but if "Thyroxine" is an option, it is the most specific answer for a receptor located permanently on the chromatin.

Q: Which of the following is secreted by the pineal gland?

Melatonin. **Explanation:** The **pineal gland** (epiphysis cerebri) is a small, pine-cone-shaped endocrine gland located in the midline of the brain, behind the third ventricle. Its primary function is the synthesis and secretion of **Melatonin**, a hormone derived from the amino acid **Tryptophan**. **1. Why Melatonin is correct:** Melatonin is synthesized via a pathway involving Serotonin. Its secretion is strictly regulated by the light-dark cycle (circadian rhythm). Light signals from the retina travel via the suprachiasmatic nucleus (SCN) to the pineal gland; darkness stimulates melatonin release, while light inhibits it. It plays a crucial role in regulating the sleep-wake cycle and has antioxidant properties. **2. Why the other options are incorrect:** * **Melanin (A):** This is a pigment produced by **melanocytes** in the skin and hair. It is not a hormone secreted by the pineal gland. (Note: MSH—Melanocyte Stimulating Hormone—is secreted by the anterior pituitary). * **ANP (C):** Atrial Natriuretic Peptide is a hormone secreted by the **atria of the heart** in response to high blood pressure/stretch. * **GH (D):** Growth Hormone is secreted by the somatotrophs of the **Anterior Pituitary gland**. **High-Yield Facts for NEET-PG:** * **Precursor:** Tryptophan → 5-Hydroxytryptophan → Serotonin → Melatonin. * **Rate-limiting enzyme:** N-acetyltransferase (NAT). * **Biological Clock:** The Suprachiasmatic Nucleus (SCN) of the hypothalamus is the master pacemaker that controls the pineal gland. * **Clinical Correlation:** Melatonin is used therapeutically for **jet lag** and delayed sleep phase syndrome. * **Brain Sand:** Calcification of the pineal gland (corpora arenacea) is a common radiological finding in adults, used as a midline marker on X-rays/CT scans.

Q: Diurnal variation in eosinophil count is related to:

Cortisol. **Explanation:** The diurnal variation of eosinophil counts is inversely related to the circulating levels of **Cortisol**. **1. Why Cortisol is correct:** Cortisol follows a strict circadian rhythm, peaking in the early morning (approx. 8 AM) and reaching its nadir around midnight. Cortisol exerts an **eosinopenic effect** by promoting the sequestration of eosinophils into the lymphoid tissues and bone marrow, and increasing their apoptosis. Consequently, eosinophil counts are **lowest in the morning** (when cortisol is high) and **highest at night** (when cortisol is low). This inverse relationship is a classic physiological principle often tested in hematology and endocrinology. **2. Why other options are incorrect:** * **Thyroxine (B):** While thyroid hormones influence metabolic rate, they do not exhibit a significant diurnal rhythm that acutely fluctuates the white blood cell differential. * **Growth Hormone (C):** GH is secreted in pulsatile bursts, primarily during deep sleep (Stage N3). While it has a diurnal pattern, its primary effects are on growth and metabolism, not on the immediate sequestration of eosinophils. * **Testosterone (D):** Testosterone levels are generally higher in the morning, but they do not have a direct, acute regulatory effect on the circulating eosinophil count. **Clinical Pearls for NEET-PG:** * **Mnemonic (B-E-L-L):** Cortisol causes a decrease in **B**asophils, **E**osinophils, and **L**ymphocytes, but an increase in **L**eukocytes (specifically Neutrophils) and **L**iver glycogen. * **Diagnostic Significance:** The loss of diurnal variation in cortisol is an early sign of **Cushing’s Syndrome**. * **Eosinopenia** is also seen during acute stress (due to endogenous ACTH/cortisol surge) and after the administration of exogenous glucocorticoids.

Q: About Neuropeptide Y, all are true except?

Its level decreases during starvation. **Explanation:** **Neuropeptide Y (NPY)** is one of the most potent **orexigenic** (appetite-stimulating) peptides found in the brain, primarily synthesized in the arcuate nucleus of the hypothalamus. **1. Why Option C is the Correct Answer (The "Except" Statement):** In states of negative energy balance, such as **starvation or fasting**, the body attempts to restore energy stores by increasing hunger. Therefore, **NPY levels increase significantly during starvation** to stimulate food intake. The statement that it decreases is physiologically incorrect, making it the right choice for this "except" question. **2. Analysis of Other Options:** * **Option A:** NPY acts as an antagonist to the melanocortin system. It inhibits the release of Pro-opiomelanocortin (POMC) derivatives and competes with the melanocortin signaling pathway to promote feeding. * **Option B:** To conserve energy during periods of perceived food scarcity, NPY **decreases thermogenesis** (specifically by inhibiting brown adipose tissue activity) and lowers sympathetic nervous system activity. * **Option D:** Structurally, NPY is a member of the pancreatic polypeptide family and consists of **36 amino acid residues**. **Clinical Pearls for NEET-PG:** * **Orexigenic (Hunger) Signals:** NPY, Agouti-related peptide (AgRP), Ghrelin ("Hunger hormone"). * **Anorexigenic (Satiety) Signals:** Leptin, Insulin, POMC, CART (Cocaine-and-amphetamine-regulated transcript), and CCK. * **Leptin Connection:** Leptin normally **inhibits** NPY. In obesity, leptin resistance leads to a failure to suppress NPY, contributing to overeating. * **NPY Receptors:** Primarily acts via Y1 and Y5 receptors to stimulate feeding.

Q: Basal metabolic rate (BMR) is decreased in which of the following conditions?

Hypothyroidism. **Explanation:** **Basal Metabolic Rate (BMR)** is the minimum amount of energy required by the body to maintain vital functions (like breathing and circulation) at complete physical and mental rest in a post-absorptive state. **1. Why Hypothyroidism is Correct:** Thyroid hormones ($T_3$ and $T_4$) are the primary determinants of BMR. They increase oxygen consumption and heat production in almost all tissues by increasing the activity of the $Na^+-K^+$ ATPase pump. In **hypothyroidism**, there is a deficiency of these hormones, leading to a significant decrease in cellular metabolism and oxygen consumption, thereby **decreasing the BMR** (often by 30-40%). **2. Why Incorrect Options are Wrong:** * **Exposure to cold temperature:** Cold exposure **increases** BMR as the body generates heat through shivering and non-shivering thermogenesis (activation of brown adipose tissue) to maintain core temperature. * **Hyperthyroidism:** Excess thyroid hormones stimulate metabolic pathways, leading to a marked **increase** in BMR (up to 60-100% above normal). * **Exercise:** Physical activity involves muscular contraction, which significantly **increases** energy expenditure and metabolic rate. **High-Yield Clinical Pearls for NEET-PG:** * **Surface Area Rule:** BMR is directly proportional to the surface area of the body (Rubner’s Law). * **Gender & Age:** BMR is higher in males (due to testosterone and higher muscle mass) and decreases with advancing age. * **Specific Dynamic Action (SDA):** Protein has the highest SDA (30%), meaning it increases metabolic rate the most during digestion. * **Starvation:** BMR **decreases** during prolonged fasting or starvation as an adaptive mechanism to conserve energy.

Question 1

Growth hormone increases all of the following except?

Accepted Answer

Metabolism of carbohydrates

Answer

Blood glucose concentration

Answer

Blood free fatty acid concentration

Answer

Protein synthesis

Question 2

Insulin-like growth factor-II (IGF-II) is synthesized in all of the following tissues EXCEPT:

Accepted Answer

Cartilage

Answer

Brain

Answer

Liver

Answer

Pancreas

Question 3

Which of the following acts on nuclear receptors?

Accepted Answer

Thyroxine

Answer

Glucocorticoids

Answer

Progesterone

Answer

Insulin

Question 4

Which of the following is secreted by the pineal gland?

Accepted Answer

Melatonin

Answer

Melanin

Answer

ANP

Answer

GH

Question 5

All are true about the Hypothalamus-pituitary-Adrenal axis except?

Accepted Answer

Corticotropin-releasing hormone (CRH) stimulates the zona fasciculata leading to increased cortisol production.

Answer

CRH and vasopressin are released from neurosecretory nerve terminals at the median eminence.

Answer

Cortisol produced in the adrenal cortex will negatively feedback.

Answer

Epinephrine and norepinephrine will positively feedback to the pituitary.

Question 6

Diurnal variation in eosinophil count is related to:

Accepted Answer

Cortisol

Answer

Thyroxine

Answer

Growth hormone

Answer

Testosterone

Question 7

Which of the following sources of cholesterol is most important for sustaining adrenal steroidogenesis when it occurs at a high rate for a long time?

Accepted Answer

Cholesterol in LDL particles

Answer

De novo synthesis of cholesterol from acetate

Answer

Cholesterol in the plasma membrane

Answer

Cholesterol in lipid droplets within adrenal cortical cells

Question 8

Which of the following is NOT a function of insulin?

Accepted Answer

Increased protein synthesis in muscle

Answer

Increased glucose uptake in muscle

Answer

Increased lipolysis in adipose tissue

Answer

Decreased gluconeogenesis in the liver

Question 9

About Neuropeptide Y, all are true except?

Accepted Answer

Its level decreases during starvation

Answer

It is mediated through melanocorticotropin hormone

Answer

Decreases thermogenesis

Answer

Contains 36 aminoacid residues

Question 10

Basal metabolic rate (BMR) is decreased in which of the following conditions?

Accepted Answer

Hypothyroidism

Answer

Exposure to cold temperature

Answer

Hyperthyroidism

Answer

Exercise

Endocrinology — MCQs

Endocrinology — MCQs

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