Endocrinology Practice Questions

Q: Excess secretion of aldosterone causes all except?

Very high Na+ in plasma. This question tests your understanding of the **Aldosterone Escape** phenomenon and the renal handling of sodium. ### Why "Very high Na+ in plasma" is the Correct Answer While aldosterone increases sodium reabsorption in the distal convoluted tubule and collecting ducts, it does **not** cause a significant rise in plasma sodium concentration (hypernatremia). This is because: 1. **Water follows Sodium:** As sodium is reabsorbed, water is reabsorbed osmotically in equal proportions, maintaining an isotonic state. 2. **Aldosterone Escape:** The initial increase in ECF volume triggers the release of **Atrial Natriuretic Peptide (ANP)** and increases the pressure natriuresis. This causes the kidneys to "escape" the sodium-retaining effects, leading to a new steady state where sodium excretion matches intake. Thus, plasma Na+ remains within the normal or high-normal range, never "very high." ### Explanation of Incorrect Options * **A. Increased ECF:** Aldosterone causes sodium and water retention, which directly expands the extracellular fluid volume. * **C. Increased Blood Pressure:** ECF expansion leads to increased cardiac output and peripheral resistance, resulting in hypertension (a hallmark of Conn’s Syndrome). * **D. Natriuresis:** This refers to the "Aldosterone Escape." Once the ECF volume expands to a certain point (usually after 2-3 kg of weight gain), the body compensates by increasing sodium excretion (natriuresis) to prevent edema. ### High-Yield Clinical Pearls for NEET-PG * **Conn’s Syndrome Triad:** Hypertension, Hypokalemia, and Metabolic Alkalosis. * **The "Escape" Rule:** Aldosterone escape explains why patients with primary hyperaldosteronism have **hypertension but no clinical edema.** * **Electrolytes:** Aldosterone acts on Principal cells (reabsorb Na+, secrete K+) and Alpha-intercalated cells (secrete H+). Therefore, excess leads to **Hypokalemia** and **Alkalosis**.

Q: Which one of the following is present intracellularly in muscle cells?

Corticosteroid. **Explanation:** The location of a hormone's receptor—and thus its presence inside a cell—is primarily determined by its **solubility**. **1. Why Corticosteroid is correct:** Corticosteroids (like cortisol) are **steroid hormones** derived from cholesterol. Being lipophilic (lipid-soluble), they easily diffuse across the phospholipid bilayer of the plasma membrane. Once inside the muscle cell, they bind to **intracellular receptors** (specifically cytoplasmic receptors), which then translocate to the nucleus to act as transcription factors. Therefore, corticosteroids are physically present within the intracellular compartment to exert their effects. **2. Why the other options are incorrect:** * **Insulin (Option A):** A peptide hormone that is water-soluble. It cannot cross the lipid membrane and binds to a **Tyrosine Kinase receptor** located on the cell surface. * **Epinephrine (Option C):** A catecholamine (amino acid derivative). Despite its small size, it is polar and binds to **G-protein coupled receptors (GPCRs)** on the plasma membrane. * **Glucagon (Option D):** A peptide hormone that binds to membrane-bound GPCRs to activate the cAMP second messenger system. **High-Yield NEET-PG Pearls:** * **Intracellular Receptors:** Remember the mnemonic **"VET TV"** (Vitamin D, Estrogen, Testosterone, Thyroid hormones (T3/T4), and Vitamin A/Retinoids). Note that while Thyroid hormones are amines, they are the exception and act intracellularly (nuclear receptors). * **Cytoplasmic vs. Nuclear:** Most steroid receptors (like Corticosteroids) are **cytoplasmic**, while Thyroid and Estrogen receptors are primarily **nuclear**. * **Mechanism of Action:** Hormones with intracellular receptors have a slower onset but longer duration of action compared to membrane-binding hormones because they alter gene transcription.

Q: A semen analysis reveals 15 million sperm/ml with a total of 15% motile sperm. What does this signify?

Oligoasthenozoospermia. **Explanation:** The correct answer is **Oligoasthenozoospermia** because the semen analysis shows abnormalities in both sperm count and sperm motility. 1. **Oligozoospermia:** According to the WHO (2021) criteria, the lower reference limit for sperm concentration is **15 million sperm/ml**. While 15 million is exactly at the cutoff, any value below or at the borderline in clinical scenarios—especially when combined with other defects—is categorized under the "Oligo" (few) spectrum. 2. **Asthenozoospermia:** This refers to reduced sperm motility. The WHO standard requires at least **40% total motility** (or 32% progressive motility). A value of **15% motility** is significantly below the normal range. Since both concentration and motility are impaired, the combined term **Oligoasthenozoospermia** is used. **Analysis of Incorrect Options:** * **Aspermia:** The complete absence of semen (ejaculate), not just sperm. * **Asthenozoospermia:** Only addresses the motility defect (15%) but ignores the borderline/low sperm count. * **Oligozoospermia:** Only addresses the low sperm count but ignores the motility defect. **NEET-PG High-Yield Pearls:** * **Azoospermia:** Absence of sperm in the ejaculate. * **Teratozoospermia:** Abnormal sperm morphology (<4% normal forms). * **Necrozoospermia:** All sperm in the ejaculate are dead. * **Globozoospermia:** A rare condition where sperm have round heads and lack an acrosome ("round-headed sperm"), leading to infertility. * **Normal Semen Volume:** 1.5 to 5.0 ml. * **Fructose:** Produced by seminal vesicles; its absence suggests bilateral congenital absence of the vas deferens or ejaculatory duct obstruction.

Q: Which of the following is most likely to result in a decreased rate of aldosterone release?

A decrease in IP3 in cells of the zona glomerulosa. **Explanation:** Aldosterone is synthesized and secreted by the **zona glomerulosa** of the adrenal cortex. Its release is primarily regulated by the **Renin-Angiotensin-Aldosterone System (RAAS)** and serum potassium levels. **Why Option D is Correct:** Both Angiotensin II and extracellular Potassium (K+) stimulate the zona glomerulosa cells via the **Gq-protein coupled receptor** pathway. Activation of this pathway stimulates the enzyme Phospholipase C, which cleaves PIP2 into **Inositol triphosphate (IP3)** and Diacylglycerol (DAG). IP3 triggers the release of intracellular calcium, which is the crucial signal for aldosterone synthesis. Therefore, a **decrease in IP3** would interrupt this signaling cascade, leading to a decreased rate of aldosterone release. **Why Other Options are Incorrect:** * **Option A:** Increased renin leads to increased Angiotensin II, which is a potent stimulator of aldosterone release. * **Option B:** A rise in serum potassium directly depolarizes the zona glomerulosa cell membrane, opening voltage-gated calcium channels and increasing aldosterone secretion to facilitate K+ excretion. * **Option C:** A fall in renal blood pressure (detected by the juxtaglomerular apparatus) triggers renin release, ultimately increasing aldosterone to promote sodium and water retention. **High-Yield NEET-PG Pearls:** * **Primary Stimuli:** The two most important regulators of aldosterone are **Angiotensin II** and **Hyperkalemia**. * **ACTH Role:** ACTH has a "permissive" effect; it is necessary for aldosterone secretion but does not regulate its minute-to-minute levels (unlike cortisol). * **Atrial Natriuretic Peptide (ANP):** This is the primary hormone that **inhibits** aldosterone secretion by antagonizing the RAAS. * **Mechanism:** Aldosterone acts on the **Principal cells** of the late distal tubule and collecting duct to increase Na+ reabsorption and K+ secretion.

Q: Inactivation of cortisol into cortisone occurs mainly in which organ?

Kidney. ### Explanation The conversion of active **cortisol** to inactive **cortisone** is a protective mechanism primarily occurring in the **Kidney**. **1. Why Kidney is the Correct Answer:** The kidney expresses high levels of the enzyme **11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2)**. This enzyme inactivates cortisol into cortisone. This is crucial because cortisol has a high affinity for **Mineralocorticoid Receptors (MR)** in the distal nephron. Without this inactivation, the high circulating levels of cortisol would overwhelm the MR, leading to excessive sodium retention and potassium loss (mimicking hyperaldosteronism). **2. Why Other Options are Incorrect:** * **Liver:** The liver primarily performs the **reverse** reaction. It contains **11β-HSD type 1**, which converts inactive cortisone back into active cortisol (activation). * **Adrenals:** The adrenal cortex is the site of cortisol **synthesis** (specifically the Zona Fasciculata), not its primary site of inactivation. * **Lungs:** While the lungs possess some metabolic activity, they are not the principal site for the systemic inactivation of cortisol via the 11β-HSD2 pathway. **3. Clinical Pearls for NEET-PG:** * **Apparent Mineralocorticoid Excess (AME):** A genetic deficiency of 11β-HSD2 (or inhibition by **Glycyrrhizic acid** found in **Licorice**) prevents cortisol inactivation. This leads to hypertension, hypokalemia, and metabolic alkalosis despite low aldosterone levels. * **11β-HSD1 (Liver):** Bidirectional but mainly acts as a **reductase** (Cortisone → Cortisol). * **11β-HSD2 (Kidney):** Unidirectional **dehydrogenase** (Cortisol → Cortisone). * **Cortisol vs. Aldosterone:** Cortisol circulates at concentrations ~1000 times higher than aldosterone; hence, 11β-HSD2 is the "gatekeeper" of the mineralocorticoid receptor.

Q: Which hormone causes increased food intake?

Ghrelin. **Explanation:** The regulation of food intake is controlled by the hypothalamus, specifically through the interplay of **orexigenic** (appetite-stimulating) and **anorexigenic** (appetite-suppressing) signals. **Why Ghrelin is Correct:** Ghrelin is a peptide hormone secreted primarily by the **P/D1 cells of the stomach fundus**. It is known as the "hunger hormone" because it is the only peripheral hormone that stimulates food intake (orexigenic). It acts on the **Arcuate Nucleus** of the hypothalamus to stimulate **NPY (Neuropeptide Y)** and **AgRP (Agouti-related peptide)** neurons, which increase appetite and growth hormone secretion. Ghrelin levels rise sharply before meals and fall immediately after eating. **Why Other Options are Incorrect:** * **Leptin:** Produced by adipocytes, it is a long-term satiety signal. It inhibits NPY/AgRP neurons and stimulates POMC neurons, thereby **decreasing** food intake. * **CART (Cocaine-and-Amphetamine-Regulated Transcript):** This is a potent **anorexigenic** neurotransmitter found in the hypothalamus that decreases appetite. * **Serotonin (5-HT):** In the CNS, serotonin acts as a **satiety signal**. Drugs that increase serotonin levels (like fenfluramine) were historically used to suppress appetite. **High-Yield Clinical Pearls for NEET-PG:** * **Prader-Willi Syndrome:** Characterized by hyperphagia and obesity due to pathologically **elevated Ghrelin levels**. * **Sleep Deprivation:** Increases Ghrelin and decreases Leptin, leading to weight gain. * **Vagus Nerve:** Ghrelin signals are also transmitted via the vagus nerve to the brainstem. * **Post-Gastric Bypass:** Weight loss is partly attributed to a significant **reduction in Ghrelin** levels due to the bypass of the stomach fundus.

Q: Which hormone acts on intracellular receptors?

Thyroid-stimulating hormone (TSH). **Explanation:** The mechanism of hormone action is determined by the chemical nature of the hormone. Hormones that are **lipid-soluble** (lipophilic) can cross the cell membrane and bind to **intracellular receptors** (cytoplasmic or nuclear), whereas water-soluble hormones bind to cell surface receptors. **Why Option A is Correct:** **Thyroid-stimulating hormone (TSH)** is a glycoprotein hormone. *Note: There appears to be a discrepancy in the provided key.* In standard physiology, TSH binds to G-protein coupled receptors (GPCR) on the **cell surface**. However, if the question intended to refer to **Thyroid Hormones (T3/T4)**, they are the classic examples of hormones acting on **intracellular (nuclear) receptors**. If this is a recall-based question where TSH is the keyed answer, it is often a common point of confusion with T3/T4; however, strictly speaking, Steroids, Vitamin D, and Thyroid hormones (T3/T4) are the primary groups using intracellular receptors. **Why Other Options are Incorrect:** * **B. FSH:** A glycoprotein hormone that acts via the **cAMP second messenger system** through cell surface GPCRs. * **C. Glucagon:** A peptide hormone that binds to Gs-coupled receptors on the cell membrane, activating adenylate cyclase. * **D. Epinephrine:** A catecholamine that acts on membrane-bound **α and β-adrenergic receptors**. **High-Yield NEET-PG Pearls:** 1. **Nuclear Receptors:** Remember the mnemonic **"PET TV"** (Progesterone, Estrogen, Testosterone, Thyroid hormones, Vitamin D/A). 2. **Cytoplasmic Receptors:** Primarily used by **Glucocorticoids** and **Mineralocorticoids**. 3. **Second Messengers:** Most peptide hormones use **cAMP** (e.g., ACTH, LH, FSH, PTH), while others like Oxytocin and GnRH use the **IP3/DAG** pathway. 4. **Insulin & Growth Factors:** Utilize **Tyrosine Kinase** activity (enzyme-linked receptors).

Q: Vasopressin is secreted by which nucleus?

Supraoptic nucleus. **Explanation:** The posterior pituitary hormones, **Vasopressin (ADH)** and **Oxytocin**, are synthesized in the hypothalamus and transported via the hypothalamo-hypophyseal tract to the posterior pituitary for storage and release. 1. **Why Supraoptic Nucleus is Correct:** While both the Supraoptic Nucleus (SON) and the Paraventricular Nucleus (PVN) synthesize both hormones, they do so in different proportions. The **Supraoptic nucleus** is the primary site for **Vasopressin (ADH)** synthesis (roughly 5/6th of the total ADH), while the Paraventricular nucleus is primarily responsible for Oxytocin. 2. **Analysis of Incorrect Options:** * **Preoptic Nucleus:** This area is primarily involved in thermoregulation (the "heat loss center") and the release of Gonadotropin-Releasing Hormone (GnRH). * **Paraventricular Nucleus:** As mentioned, this is the primary site for **Oxytocin** synthesis. It also plays a role in secreting CRH and TRH. * **Posterior Nucleus:** This nucleus is part of the hypothalamus involved in "heat production" (shivering) and sympathetic nervous system activation. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** **S**-**O**-**V**-**A** (**S**upra**O**ptic = **V**asopressin; **P**ara**V**entricular = **O**xytocin). * **Precursor:** Vasopressin is synthesized as a preprohormone called **Prepro-pressophysin**. * **Carrier Protein:** Both hormones are transported down axons bound to proteins called **Neurophysins** (Neurophysin II for ADH). * **Lesion Site:** A lesion in the hypothalamus or the tract (above the median eminence) leads to **Central Diabetes Insipidus**, whereas a lesion of the posterior pituitary alone often results in only transient deficiency because the hypothalamus continues to secrete the hormone into the portal circulation.

Question 1

Excess secretion of aldosterone causes all except?

Accepted Answer

Very high Na+ in plasma

Answer

Increased extracellular fluid

Answer

Increased blood pressure

Answer

Natriuresis

Question 2

Which one of the following is present intracellularly in muscle cells?

Accepted Answer

Corticosteroid

Answer

Insulin

Answer

Epinephrine

Answer

Glucagon

Question 3

A semen analysis reveals 15 million sperm/ml with a total of 15% motile sperm. What does this signify?

Accepted Answer

Oligoasthenozoospermia

Answer

Aspermia

Answer

Asthenozoospermia

Answer

Oligozoospermia

Question 4

Which of the following is most likely to result in a decreased rate of aldosterone release?

Accepted Answer

A decrease in IP3 in cells of the zona glomerulosa

Answer

An increase in renin secretion by the kidney

Answer

A rise in serum potassium

Answer

A fall in blood pressure in the kidney

Question 5

Most peptide and protein hormones are synthesized as what?

Accepted Answer

A preprohormone

Answer

A secretagogue

Answer

A pleiotropic hormone

Answer

Proopiomelanocortin (POMC)

Question 6

Inactivation of cortisol into cortisone occurs mainly in which organ?

Accepted Answer

Kidney

Answer

Lungs

Answer

Liver

Answer

Adrenals

Question 7

Which hormone causes increased food intake?

Accepted Answer

Ghrelin

Answer

Leptin

Answer

Cart

Answer

Serotonin

Question 8

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 9

Which hormone acts on intracellular receptors?

Accepted Answer

Thyroid-stimulating hormone (TSH)

Answer

Follicle-stimulating hormone (FSH)

Answer

Glucagon

Answer

Epinephrine

Question 10

Vasopressin is secreted by which nucleus?

Accepted Answer

Supraoptic nucleus

Answer

Preoptic nucleus

Answer

Paraventricular nucleus

Answer

Posterior nucleus

Endocrinology — MCQs

Endocrinology — MCQs

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