Endocrinology Practice Questions

Q: Dwarfism is caused by all EXCEPT:

Castration before puberty. **Explanation:** The core concept in this question is the distinction between **short stature (dwarfism)** and **delayed epiphyseal closure**. **Why Castration before puberty is the correct answer:** Castration leads to a deficiency of sex steroids (testosterone/estrogen). These hormones are essential for the "pubertal growth spurt" and, more importantly, for the **closure of epiphyseal plates**. In their absence, the epiphyses remain open for a longer duration, allowing growth to continue under the influence of Growth Hormone (GH). This results in **Eunuchoidism**, characterized by tall stature and long limbs (the lower segment being longer than the upper segment), rather than dwarfism. **Analysis of incorrect options:** * **Thyroid deficiency (Hypothyroidism):** Thyroid hormones are permissive for GH action. Congenital hypothyroidism (Cretinism) leads to stunted physical and mental growth, resulting in disproportionate dwarfism. * **Growth hormone deficiency:** GH is the primary driver of postnatal linear growth. Deficiency (Pituitary dwarfism) leads to proportionate dwarfism with normal mental development. * **GH-receptor unresponsiveness:** Also known as **Laron Dwarfism**. Here, GH levels are actually high, but the receptors are defective, leading to a failure in IGF-1 production and subsequent short stature. **High-Yield Clinical Pearls for NEET-PG:** * **Laron Dwarfism:** High GH, Low IGF-1. * **African Pygmies:** Normal GH, Low IGF-1 (post-receptor defect). * **Most common cause of Dwarfism:** Achondroplasia (autosomal dominant, FGFR3 mutation). * **Bone Age vs. Chronological Age:** In endocrine dwarfism (GH/Thyroid deficiency), bone age is typically delayed compared to chronological age.

Q: Cyclic AMP (cAMP) acts as a second messenger of which hormone?

Follicle-stimulating hormone (FSH). ### Explanation **1. Why FSH is Correct:** Follicle-stimulating hormone (FSH) is a peptide hormone that binds to G-protein coupled receptors (GPCRs) on the cell membrane. Upon binding, it activates the enzyme **adenylyl cyclase**, which converts ATP into **cyclic AMP (cAMP)**. cAMP then acts as a second messenger to activate Protein Kinase A (PKA), leading to the physiological effects in the gonads (e.g., follicular development in females and spermatogenesis in males). Other hormones using the cAMP pathway include LH, ACTH, TSH, Glucagon, and PTH. **2. Why the Other Options are Incorrect:** * **Growth Hormone (GH):** GH utilizes the **JAK-STAT pathway** (Janus Kinase-Signal Transducer and Activator of Transcription). It binds to a receptor that lacks intrinsic kinase activity but recruits cytoplasmic kinases. * **Thyroxine (T4):** As a lipid-soluble thyroid hormone, it crosses the cell membrane and binds to **nuclear receptors**. It acts as a transcription factor to alter gene expression directly, requiring no second messenger. * **Insulin:** Insulin binds to a receptor with intrinsic **Tyrosine Kinase** activity. This triggers autophosphorylation and activates the MAP kinase and PI3K pathways. **3. High-Yield Clinical Pearls for NEET-PG:** * **cAMP Pathway Mnemonic:** "FLAT ChAMP" (FSH, LH, ACTH, TSH, CRH, hCG, ADH [V2 receptor], MSH, PTH). * **IP3/DAG Pathway Mnemonic:** "GOAT HAG" (GnRH, Oxytocin, ADH [V1 receptor], TRH, Histamine, Angiotensin II, Gastrin). * **cGMP Pathway:** Used by ANP, BNP, and Nitric Oxide (NO). * **Steroid/Thyroid Hormones:** Always remember they use intracellular/nuclear receptors because they are lipophilic.

Q: A patient has an elevated plasma thyroxine (T4) concentration, a low plasma TSH concentration, and her thyroid gland is smaller than normal. What is the most likely explanation for these findings?

The patient is taking thyroid extract. ### Explanation The clinical presentation described is a classic case of **Exogenous Thyrotoxicosis** (Factitious Thyrotoxicosis). **1. Why the Correct Answer is Right:** When a patient takes exogenous thyroid extract (T4), the plasma T4 levels rise. This high concentration of T4 exerts **negative feedback** on the anterior pituitary, significantly inhibiting the secretion of Thyroid Stimulating Hormone (TSH). Since TSH is the primary trophic hormone responsible for the growth and maintenance of the thyroid gland, its chronic suppression leads to **disuse atrophy**, resulting in a thyroid gland that is smaller than normal. **2. Analysis of Incorrect Options:** * **Option A (Pituitary Lesion):** While a pituitary lesion would cause low TSH, it would lead to **low** T4 levels (Secondary Hypothyroidism), not elevated T4. * **Option B (Graves' Disease):** In Graves' disease, Thyroid Stimulating Immunoglobulins (TSI) mimic TSH, leading to high T4 and low TSH. However, TSI also stimulates the growth of the gland, typically causing a **diffuse goiter** (enlarged gland), not a small gland. * **Option C (Propylthiouracil):** PTU inhibits thyroid hormone synthesis. This would lead to low T4 and a compensatory **increase in TSH**, which would likely cause an enlarged thyroid (goiter). **3. NEET-PG High-Yield Pearls:** * **Trophic Effect:** TSH is essential for thyroid cell hypertrophy and hyperplasia. Low TSH = Atrophy; High TSH = Goiter. * **Radioactive Iodine Uptake (RAIU):** In exogenous thyroid intake, RAIU is **decreased** (low) because the endogenous gland is suppressed. In Graves' disease, RAIU is **increased** (high). * **Thyroglobulin Levels:** Low serum thyroglobulin in a thyrotoxic patient is a key marker for exogenous hormone intake, as thyroglobulin is only released during endogenous hormone production.

Q: Glucagon acts via which second messenger system?

cAMP. **Explanation:** Glucagon is a peptide hormone produced by the alpha cells of the pancreas. It exerts its primary metabolic effects by binding to specific **G Protein-Coupled Receptors (GPCRs)** on the surface of hepatocytes. 1. **Why cAMP is correct:** When glucagon binds to its receptor, it activates the **Gs (stimulatory) protein**, which in turn stimulates the enzyme **Adenylyl Cyclase**. This enzyme converts ATP into **cyclic AMP (cAMP)**. Increased levels of cAMP activate **Protein Kinase A (PKA)**, leading to the phosphorylation of key enzymes that promote glycogenolysis and gluconeogenesis while inhibiting glycogenesis. 2. **Why other options are incorrect:** * **cGMP:** This is the second messenger for Atrial Natriuretic Peptide (ANP) and Nitric Oxide (NO), primarily involved in vasodilation. * **Cytoplasmic Ca²⁺:** This is typically associated with the **Gq pathway** (via IP3/DAG), used by hormones like Oxytocin, Vasopressin (V1 receptors), and α1-adrenergic agonists. * **Intracellular K⁺:** While ion channels are involved in insulin secretion (ATP-sensitive K+ channels), they do not serve as the primary second messenger for glucagon signaling. **High-Yield Clinical Pearls for NEET-PG:** * **Glucagon in Beta-blocker Overdose:** Glucagon is the **antidote of choice** for beta-blocker poisoning. It bypasses blocked beta-receptors to increase cAMP directly in cardiac myocytes, exerting positive inotropic and chronotropic effects. * **Other cAMP users:** Remember the mnemonic "FLAT ChAMP" (FSH, LH, ACTH, TSH, CRH, hCG, ADH (V2), MSH, PTH, and Glucagon). * **Insulin vs. Glucagon:** While Glucagon uses cAMP, **Insulin** uses a **Receptor Tyrosine Kinase** pathway.

Q: Which of the following changes occur in bone growth?

Increased osteocalcin. ### Explanation **Correct Answer: D. Increased osteocalcin** **Why it is correct:** Bone growth and remodeling are driven by the activity of **osteoblasts** (bone-forming cells). **Osteocalcin** (also known as Bone Gamma-Carboxyglutamic Acid Protein) is a non-collagenous protein hormone synthesized exclusively by osteoblasts. It plays a crucial role in bone mineralization and calcium ion binding. Because its synthesis is specific to osteoblasts, serum levels of osteocalcin are considered a highly specific **biochemical marker of bone formation** and turnover. During periods of active bone growth, osteoblast activity increases, leading to elevated osteocalcin levels. **Why the other options are incorrect:** * **A. Increased acid phosphatase:** Tartrate-resistant acid phosphatase (TRAP) is a marker of **osteoclast** activity (bone resorption), not bone growth. * **B. Increased urinary calcium:** High urinary calcium (hypercalciuria) is typically a sign of bone resorption or impaired renal reabsorption, often seen in conditions like hyperparathyroidism or immobilization, rather than healthy bone growth. * **C. Increased bone nucleotidase:** While 5'-nucleotidase is a marker for liver/biliary disease, it is not a specific or standard marker for bone growth or mineralization. **NEET-PG High-Yield Pearls:** * **Markers of Bone Formation:** Osteocalcin, Bone-specific Alkaline Phosphatase (ALP), and Procollagen type 1 N-terminal propeptide (P1NP). * **Markers of Bone Resorption:** Urinary hydroxyproline, Pyridinoline cross-links, and Serum TRAP. * **Vitamin K Dependency:** Osteocalcin requires Vitamin K for carboxylation to become functional; thus, Vitamin K deficiency can impair bone mineralization. * **Metabolic Link:** Osteocalcin also acts as a hormone that increases insulin secretion and sensitivity, linking bone metabolism to energy homeostasis.

Q: Which of the following hormones is not involved in the regulation of food intake?

Gastrin. The regulation of food intake is governed by the **hypothalamus**, which integrates signals from peripheral hormones to balance hunger (orexigenic) and satiety (anorexigenic) signals. **Why Gastrin is the Correct Answer:** **Gastrin** is a gastrointestinal hormone primarily responsible for stimulating **gastric acid (HCl) secretion** from parietal cells and promoting the growth of the gastric mucosa. While it is vital for digestion, it does not play a direct role in the hypothalamic regulation of appetite or long-term energy balance. **Analysis of Incorrect Options:** * **Ghrelin:** Known as the "hunger hormone," it is secreted by P/D1 cells of the stomach fundus. It is the only major peripheral **orexigenic** hormone; it stimulates the NPY/AgRP neurons in the arcuate nucleus to increase food intake. * **Insulin:** Secreted by the pancreas in response to high blood glucose, insulin acts as a **satiety signal**. It crosses the blood-brain barrier to inhibit food intake and regulate long-term energy homeostasis. * **Leptin:** Produced by adipose tissue (the "satiety hormone"), it signals the brain about the body's fat stores. It stimulates POMC/CART neurons and inhibits NPY/AgRP neurons, thereby **decreasing food intake**. **High-Yield Clinical Pearls for NEET-PG:** * **Arcuate Nucleus:** The "master center" for appetite regulation in the hypothalamus. * **Prader-Willi Syndrome:** Characterized by hyperphagia and obesity due to extremely high levels of **Ghrelin**. * **Cholecystokinin (CCK):** Another important GI hormone that acts as a short-term satiety signal (unlike Gastrin). * **Leptin Resistance:** The primary mechanism behind obesity, where the brain fails to respond to high levels of circulating leptin.

Q: What is the primary function of Follistatin?

Prevents interaction of activin with receptor. **Explanation:** **Follistatin** is a glycoprotein primarily produced by the folliculostellate cells of the anterior pituitary and granulosa cells of the ovary. Its primary physiological role is to act as an **activin-binding protein**. 1. **Why Option C is Correct:** Follistatin functions as an activin antagonist. It binds directly to activin with high affinity, effectively "sequestering" it. This prevents activin from binding to its specific serine/threonine kinase receptors on the cell surface. Since activin is a potent stimulator of FSH synthesis, follistatin’s neutralization of activin leads to a significant reduction in FSH secretion. 2. **Why Other Options are Incorrect:** * **Option A & B:** While follistatin ultimately leads to decreased FSH, its *primary* biochemical mechanism is not a direct modulation of the gonadotrope cell's overall function, but rather the specific inhibition of the activin signaling pathway. * **Option D:** Activin stimulates FSH beta gene expression. Because follistatin inhibits activin, it **suppresses** (rather than stimulates) FSH beta gene expression. **High-Yield NEET-PG Pearls:** * **The TGF-β Superfamily:** Activin, Inhibin, and Follistatin are all part of this family and regulate the HPO axis. * **Activin vs. Inhibin:** Activin *increases* FSH; Inhibin *decreases* FSH. * **Follistatin’s Dual Role:** Beyond the pituitary, follistatin plays a role in muscle growth by binding to and inhibiting **Myostatin** (a negative regulator of muscle mass). * **Clinical Correlation:** Elevated follistatin levels are often observed in Polycystic Ovary Syndrome (PCOS), contributing to the characteristic arrest of follicular development.

Q: A person sustains head trauma leading to a transaction of the pituitary stalk. All can be a consequence of this, except?

Diabetes mellitus. **Explanation:** Pituitary stalk transection (disruption of the infundibulum) disconnects the hypothalamus from the pituitary gland, leading to significant endocrine disturbances. **Why Diabetes Mellitus is the correct answer:** Diabetes Mellitus is a disorder of insulin deficiency or resistance related to the pancreas. Pituitary stalk injury actually leads to a **deficiency of Growth Hormone (GH) and ACTH (Cortisol)**. Since GH and Cortisol are "diabetogenic" (counter-regulatory) hormones that increase blood glucose, their absence increases insulin sensitivity and can lead to **hypoglycemia**, not Diabetes Mellitus. **Analysis of other options:** * **Diabetes Insipidus (DI):** The posterior pituitary stores ADH produced in the hypothalamus. Stalk transection halts the transport of ADH, leading to Central DI (polyuria and polydipsia). * **Hyperprolactinemia:** Prolactin is the only pituitary hormone under tonic **inhibition** by hypothalamic Dopamine (Prolactin Inhibiting Factor). Disruption of the stalk prevents dopamine from reaching the anterior pituitary, causing "disinhibition" and a rise in prolactin levels. * **SIADH:** While DI is more common, head trauma or the "triphasic response" following stalk injury can cause a transient, inappropriate release of stored ADH from the degenerating posterior pituitary terminals, leading to SIADH. **High-Yield Clinical Pearls for NEET-PG:** * **The Triphasic Response in Stalk Injury:** 1. Initial DI (axonal shock), 2. Transient SIADH (leakage of stored ADH), 3. Permanent DI (death of neurons). * **The "Stalk Effect":** Any lesion compressing the stalk (e.g., Craniopharyngioma) causes hyperprolactinemia, but levels are usually <200 ng/mL (unlike Prolactinomas). * **Panhypopituitarism:** Stalk transection leads to a deficiency of all anterior pituitary hormones *except* Prolactin.

Q: All of the following are glycoproteins, EXCEPT:

GH. **Explanation:** The hormones of the anterior pituitary are chemically classified into three main groups: Glycoproteins, Pro-opiomelanocortin (POMC) derivatives, and Somatotropic hormones (Polypeptides). **1. Why GH is the correct answer:** **Growth Hormone (GH)** and **Prolactin (PRL)** belong to the Somatotropic hormone family. They are single-chain **polypeptides** (GH has 191 amino acids), not glycoproteins. They do not contain carbohydrate moieties and share structural similarities with human placental lactogen (hPL). **2. Why the other options are incorrect:** Options A, B, and C (**TSH, FSH, and LH**) along with the placental hormone **hCG**, form the **Glycoprotein family**. * These hormones are composed of two subunits: **Alpha (α) and Beta (β)**. * The **α-subunit is identical** in all four hormones. * The **β-subunit is unique** and confers biological and immunological specificity to each hormone. **High-Yield Clinical Pearls for NEET-PG:** * **Common α-subunit:** Because TSH, FSH, LH, and hCG share the same α-subunit, extremely high levels of hCG (as seen in Hydatidiform mole) can cross-react with TSH receptors, leading to hyperthyroidism. * **Acidophils vs. Basophils:** * **Acidophils** secrete GH and Prolactin (Mnemonic: **GPA** - **G**rowth hormone, **P**rolactin are **A**cidophils). * **Basophils** secrete the glycoproteins TSH, FSH, and LH (Mnemonic: **B-FLAT** - **B**asophils: **F**SH, **L**H, **A**CTH, **T**SH). * **Smallest Pituitary Hormone:** Vasopressin/ADH (9 amino acids). * **Largest Pituitary Hormone:** GH (191 amino acids).

Question 1

Dwarfism is caused by all EXCEPT:

Accepted Answer

Castration before puberty

Answer

Thyroid deficiency

Answer

Growth hormone deficiency

Answer

GH-receptor unresponsiveness

Question 2

Cyclic AMP (cAMP) acts as a second messenger of which hormone?

Accepted Answer

Follicle-stimulating hormone (FSH)

Answer

Growth hormone

Answer

Thyroxine

Answer

Insulin

Question 3

A patient has an elevated plasma thyroxine (T4) concentration, a low plasma TSH concentration, and her thyroid gland is smaller than normal. What is the most likely explanation for these findings?

Accepted Answer

The patient is taking thyroid extract

Answer

A lesion in the anterior pituitary that prevents TSH secretion

Answer

Graves' disease

Answer

The patient is taking propylthiouracil

Question 4

Glucagon acts via which second messenger system?

Accepted Answer

cAMP

Answer

cGMP

Answer

Cytoplasmic Ca+

Answer

Intracellular K+

Question 5

What is the direct action of parathyroid hormone (PTH)?

Accepted Answer

Controls the rate of formation of 1,25-dihydroxycholecalciferol

Answer

Controls the rate of 25-hydroxycholecalciferol formation

Answer

Controls the rate of calcium transport in the mucosa of the small intestine

Answer

Controls the rate of formation of calcium-binding protein

Question 6

Which of the following changes occur in bone growth?

Accepted Answer

Increased osteocalcin

Answer

Increased acid phosphatase

Answer

Increased urinary calcium

Answer

Increased bone nucleotidase

Question 7

Which of the following hormones is not involved in the regulation of food intake?

Accepted Answer

Gastrin

Answer

Ghrelin

Answer

Insulin

Answer

Leptin

Question 8

What is the primary function of Follistatin?

Accepted Answer

Prevents interaction of activin with receptor

Answer

Decreases gonadotrope function

Answer

Increases gonadotrope function

Answer

Stimulates FSH beta gene expression

Question 9

A person sustains head trauma leading to a transaction of the pituitary stalk. All can be a consequence of this, except?

Accepted Answer

Diabetes mellitus

Answer

SIADH

Answer

Diabetes insipidus

Answer

Hyperprolactinemia

Question 10

All of the following are glycoproteins, EXCEPT:

Accepted Answer

GH

Answer

TSH

Answer

FSH

Answer

LH

Endocrinology — MCQs

Endocrinology — MCQs

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