Endocrinology Practice Questions

Q: Most hormone levels decrease with aging. Which of the following hormones does NOT follow this trend?

Prolactin. ### Explanation The aging process is generally associated with a decline in the secretory capacity of various endocrine glands, a phenomenon often referred to as "somatopause," "andropause," or "adrenopause." However, **Prolactin** is a notable exception to this trend. #### Why Prolactin is the Correct Answer Unlike most pituitary and peripheral hormones, serum **Prolactin levels remain stable or may slightly increase** with age, particularly in men. In postmenopausal women, while there is an initial decline due to the loss of estrogen (which stimulates lactotrophs), the levels eventually stabilize and do not show the progressive, steep decline seen with other hormones. This is partly because the inhibitory dopaminergic control of prolactin may weaken with age. #### Why the Other Options are Incorrect * **A. Growth Hormone (GH):** GH secretion declines significantly with age (somatopause), leading to reduced muscle mass and increased visceral fat. * **C. Testosterone:** In men, bioavailable testosterone levels decrease by approximately 1% per year after the age of 30–40 (andropause). * **D. Aldosterone:** Aging is associated with a decrease in plasma renin activity and a subsequent decline in aldosterone levels, which can predispose the elderly to hyperkalemia. #### High-Yield NEET-PG Pearls * **Hormones that Decrease with Age:** GH, Testosterone, Estrogen, Aldosterone, DHEA (the most dramatic decline), and Melatonin. * **Hormones that Increase with Age:** **PTH** (due to Vitamin D deficiency/reduced calcium absorption), **FSH, and LH** (due to loss of negative feedback from gonads), and **Norepinephrine**. * **Thyroid Status:** TSH levels often slightly *increase* in the elderly, while T3 levels may decrease (Euthyroid Sick Syndrome is common in the elderly). * **Insulin:** While insulin levels may remain normal, **insulin resistance** increases with age.

Q: Zollinger-Ellison syndrome is due to a tumor of which of the following cell types?

G-cells. **Explanation:** **Zollinger-Ellison Syndrome (ZES)** is characterized by the development of a gastrin-secreting tumor, known as a **Gastrinoma**. 1. **Why G-cells are correct:** Gastrinomas originate from **G-cells**, which are neuroendocrine cells. While G-cells are normally found in the gastric antrum and duodenum, these tumors most commonly arise in the "Gastrinoma Triangle" (bounded by the confluence of the cystic and common bile ducts, the junction of the second and third portions of the duodenum, and the neck of the pancreas). The ectopic secretion of gastrin leads to hypergastrinemia, which causes massive hypersecretion of gastric acid, resulting in severe, recurrent peptic ulcers and secretory diarrhea. 2. **Why other options are incorrect:** * **Alpha cells:** These pancreatic islet cells secrete **glucagon**. A tumor of these cells is a Glucagonoma (presents with necrolytic migratory erythema and diabetes). * **Beta cells:** These secrete **insulin**. A tumor here is an Insulinoma (presents with Whipple’s triad of hypoglycemia). * **PP cells (F-cells):** These secrete **pancreatic polypeptide**. While they can form tumors (PPomas), they do not cause the acid-peptic symptoms seen in ZES. **Clinical Pearls for NEET-PG:** * **Diagnosis:** Best initial screening test is **Fasting Serum Gastrin** (>1000 pg/mL is diagnostic). The most sensitive provocative test is the **Secretin Stimulation Test** (Secretin normally inhibits gastrin but paradoxically increases it in ZES). * **Association:** Approximately 25% of ZES cases are associated with **Multiple Endocrine Neoplasia type 1 (MEN1)**. * **Location:** Most gastrinomas are found in the **duodenum** rather than the pancreas.

Q: Which of the following hormones has a cytoplasmic receptor?

Cortisol. **Explanation:** The location of a hormone receptor is primarily determined by the hormone's chemical nature (solubility). **1. Why Cortisol is Correct:** Cortisol is a **steroid hormone** derived from cholesterol. Being lipophilic (lipid-soluble), it easily diffuses through the lipid bilayer of the plasma membrane. Once inside the cell, it binds to specific **cytoplasmic receptors** (Type 1 Nuclear Receptors). The hormone-receptor complex then translocates into the nucleus, where it binds to Hormone Response Elements (HRE) on DNA to regulate gene transcription. **2. Why the Other Options are Incorrect:** * **Epinephrine (Option A):** A catecholamine derived from tyrosine. It is water-soluble and cannot cross the cell membrane; it binds to **G-protein coupled receptors (GPCRs)** on the cell surface. * **Insulin (Option B):** A peptide hormone. It binds to a specific **Enzyme-linked receptor** (Receptor Tyrosine Kinase) located on the cell membrane. * **FSH (Option C):** A glycoprotein (peptide) hormone. Like other pituitary hormones, it is large and polar, requiring a **cell surface GPCR** to initiate its action via the cAMP second messenger system. **3. High-Yield NEET-PG Clinical Pearls:** * **Cytoplasmic Receptors:** Primarily used by Steroids (Glucocorticoids, Mineralocorticoids, Androgens, Progesterone). * **Nucleoplasmic (Nuclear) Receptors:** Primarily used by **Thyroid hormones (T3/T4)**, Retinoic acid, and Vitamin D. Note: Though T3/T4 are amino acid derivatives, they act like steroids. * **Mnemonic for Cell Surface Receptors:** All peptide hormones + Catecholamines. * **Exception:** Estrogen receptors are predominantly found in the **nucleus**, unlike most other steroids which start in the cytoplasm.

Q: Which of the following hormones is stored the longest within a cell?

T3. **Explanation:** The duration for which a hormone is stored within a cell depends on its chemical nature and the storage mechanism of the gland. **Why T3 is the Correct Answer:** Thyroid hormones (T3 and T4) are unique because they are stored **extracellularly** in the follicular lumen as part of the **thyroglobulin** molecule (colloid). This storage mechanism is exceptionally efficient, allowing the thyroid gland to store enough hormone to supply the body’s requirements for **2 to 3 months**. This is the longest storage duration of any hormone in the human body. **Why Other Options are Incorrect:** * **Insulin (Option A):** As a peptide hormone, insulin is stored in cytosolic secretory granules. However, the pancreas typically stores only about a **5-day supply**, and it is rapidly released in response to glucose. * **PTH (Option B):** Parathyroid hormone is also a peptide hormone stored in granules within chief cells. Its storage is minimal, usually lasting only a **few hours**, as it is synthesized and secreted almost immediately in response to low serum calcium. * **Testosterone (Option D):** Steroid hormones are **not stored** to any significant degree. They are highly lipophilic and would leak through the cell membrane. Instead, they are synthesized de novo from cholesterol precursors on demand. **High-Yield NEET-PG Pearls:** * **Thyroid Exception:** Most endocrine glands store small amounts of hormones; the thyroid is the only gland that stores large quantities in an inactive form (colloid). * **Clinical Correlation:** This long storage explains why patients starting anti-thyroid drugs (like Carbimazole) take several weeks to become euthyroid—the body must first deplete the pre-stored 2-3 month supply of colloid. * **Steroid Rule:** Remember: "Steroids are made on demand, not stored."

Q: Negative Basal Metabolic Rate (BMR) is observed with which of the following?

Thyroid disturbance. **Explanation:** The **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. The **Thyroid gland** is the primary regulator of BMR. **1. Why Thyroid Disturbance is Correct:** Thyroid hormones (T3 and T4) directly regulate the metabolic activity of almost all tissues in the body by increasing oxygen consumption and mitochondrial activity. * **Hypothyroidism:** Leads to a **negative (decreased) BMR**, often falling 30% to 40% below normal. This results in symptoms like weight gain, cold intolerance, and bradycardia. * **Hyperthyroidism:** Leads to an increased BMR, often 50% to 100% above normal. **2. Why Other Options are Incorrect:** * **Pituitary Disturbance:** While the pituitary gland secretes TSH (which stimulates the thyroid), a pituitary disturbance only affects BMR *indirectly* via the thyroid axis. "Thyroid disturbance" is the more specific and direct physiological answer. * **Parathyroid Disturbance:** Parathyroid hormone (PTH) regulates calcium and phosphate homeostasis. It has no direct clinical impact on the body’s basal metabolic rate. **High-Yield Clinical Pearls for NEET-PG:** * **Surface Area Rule:** BMR is more closely related to surface area than to body weight. * **Specific Dynamic Action (SDA):** Proteins have the highest SDA (30%), meaning they increase metabolic rate significantly during digestion. * **Factors increasing BMR:** Fever (12% increase per 1°C), Pregnancy, Catecholamines (Epinephrine), and Male gender (due to testosterone). * **Gold Standard:** The most accurate way to measure BMR is via indirect calorimetry (measuring oxygen consumption).

Q: What is the function of incretin?

Increased insulin secretion. **Explanation:** **Incretins** are gut-derived hormones, primarily **Glucagon-like peptide-1 (GLP-1)** and **Glucose-dependent insulinotropic polypeptide (GIP)**. They are secreted by the enteroendocrine cells (L-cells and K-cells) of the small intestine in response to nutrient ingestion. 1. **Why Option B is Correct:** The "Incretin Effect" describes the phenomenon where oral glucose triggers a significantly higher insulin response compared to an equivalent dose of intravenous glucose. Incretins bind to receptors on pancreatic beta cells, stimulating **glucose-dependent insulin secretion**. They also suppress glucagon release and slow gastric emptying, helping to maintain postprandial glycemic control. 2. **Why Incorrect Options are Wrong:** * **Option A & C:** Heart rate and respiratory rate are primarily regulated by the autonomic nervous system and chemoreceptors. Incretins do not have a primary physiological role in cardiorespiratory stimulation. * **Option D:** Erythropoiesis is stimulated by Erythropoietin (EPO), produced mainly by the peritubular interstitial cells of the kidneys in response to hypoxia. **High-Yield Clinical Pearls for NEET-PG:** * **DPP-4 Inhibitors (e.g., Sitagliptin):** These drugs prevent the breakdown of endogenous GLP-1, prolonging its half-life. * **GLP-1 Agonists (e.g., Liraglutide, Exenatide):** These are injectable analogs used in Type 2 Diabetes that also promote weight loss. * **Key Difference:** Unlike sulfonylureas, the insulinotropic action of incretins is **glucose-dependent**, meaning they carry a much lower risk of hypoglycemia. * **Site of Secretion:** GLP-1 (L-cells of ileum/colon); GIP (K-cells of duodenum/jejunum).

Q: Insulin secretion is inhibited by which of the following substances?

Epinephrine. **Explanation:** Insulin secretion is primarily regulated by the autonomic nervous system and gastrointestinal hormones. **Why Epinephrine is correct:** Epinephrine (and Norepinephrine) acts as a potent inhibitor of insulin secretion. This occurs via the activation of **$\alpha_2$-adrenergic receptors** on the pancreatic beta cells. During "fight or flight" situations or exercise, the body needs to maintain high blood glucose levels for the brain and muscles. By inhibiting insulin, epinephrine prevents glucose storage and promotes hyperglycemia. While catecholamines can also bind to $\beta_2$ receptors (which stimulate insulin), the **$\alpha_2$ inhibitory effect is dominant.** **Why the other options are incorrect:** * **Secretin & Gastrin (Options A & D):** These are gastrointestinal hormones (Incretins). The "Incretin effect" explains why oral glucose causes a greater insulin spike than intravenous glucose. Both Secretin and Gastrin, along with GIP and GLP-1, **stimulate** insulin secretion in anticipation of rising blood glucose. * **Growth Hormone (Option C):** While GH is a counter-regulatory hormone that causes insulin resistance in peripheral tissues (diabetogenic effect), it actually **stimulates** the synthesis and secretion of insulin from the pancreas to compensate for the rising blood sugar. **High-Yield Clinical Pearls for NEET-PG:** * **Dominant Stimulus:** The most potent stimulator of insulin is **Glucose**. * **Receptor Logic:** * $\alpha_2$ stimulation = **Inhibition** of insulin. * $\beta_2$ stimulation / Parasympathetic (Vagus/ACh) = **Stimulation** of insulin. * **Somatostatin:** Produced by Delta cells, it is a potent universal inhibitor of both insulin and glucagon. * **Potassium Channels:** Insulin release is triggered by the **closure** of ATP-sensitive $K^+$ channels, leading to depolarization and $Ca^{2+}$ influx.

Q: Insulin decreases:

Lipolysis. **Explanation:** Insulin is the body’s primary **anabolic hormone**, secreted by the beta cells of the Islets of Langerhans. Its fundamental role is to promote energy storage and inhibit the breakdown of stored fuels (catabolism). **Why Lipolysis is the correct answer:** Insulin is a potent **anti-lipolytic** hormone. It inhibits the enzyme **Hormone-Sensitive Lipase (HSL)** in adipose tissue. HSL is responsible for breaking down stored triglycerides into free fatty acids and glycerol. By inhibiting HSL, insulin decreases the concentration of circulating free fatty acids, thereby promoting fat storage and preventing ketogenesis. **Analysis of Incorrect Options:** * **A. Glucose uptake:** Insulin **increases** glucose uptake in peripheral tissues (skeletal muscle and adipose tissue) by inducing the translocation of **GLUT-4** transporters to the cell membrane. * **B. Glycogen synthesis:** Insulin **increases** glycogenesis by activating the enzyme **Glycogen Synthase**, ensuring excess glucose is stored in the liver and muscles. * **C. Protein synthesis:** Insulin is anabolic for proteins; it **increases** amino acid uptake and protein synthesis while inhibiting proteolysis. **NEET-PG High-Yield Pearls:** * **GLUT-4** is the only insulin-dependent glucose transporter (found in heart, skeletal muscle, and adipose tissue). * Insulin stimulates **Lipoprotein Lipase (LPL)** in capillary walls to clear chylomicrons from the blood, but inhibits **Hormone-Sensitive Lipase (HSL)** inside adipocytes. * **Key Enzyme Regulation:** Insulin activates Phosphofructokinase (Glycolysis) and Glycogen Synthase (Glycogenesis), while inhibiting Fructose-1,6-bisphosphatase (Gluconeogenesis).

Question 1

Most hormone levels decrease with aging. Which of the following hormones does NOT follow this trend?

Accepted Answer

Prolactin

Answer

Growth hormone

Answer

Testosterone

Answer

Aldosterone

Question 2

Zollinger-Ellison syndrome is due to a tumor of which of the following cell types?

Accepted Answer

G-cells

Answer

Alpha cells

Answer

Beta cells

Answer

PP cells

Question 3

Which of the following hormones has a cytoplasmic receptor?

Accepted Answer

Cortisol

Answer

Epinephrine

Answer

Insulin

Answer

FSH

Question 4

A 35-year-old man presents with a thyroid nodule. Laboratory studies reveal elevated serum calcitonin and normal serum calcium. Which of the following mechanisms best explains the normal calcium levels in this patient despite high serum calcitonin levels?

Accepted Answer

High levels of calcitonin downregulate its receptor

Answer

Concurrent parathyroid adenoma

Answer

Concurrent parathyroid hyperplasia

Answer

Increase in parathyroid hormone in response to hypocalcemia

Question 5

Which of the following hormones is stored the longest within a cell?

Accepted Answer

T3

Answer

Insulin

Answer

PTH

Answer

Testosterone

Question 6

Negative Basal Metabolic Rate (BMR) is observed with which of the following?

Accepted Answer

Thyroid disturbance

Answer

Pituitary disturbance

Answer

Parathyroid disturbance

Answer

All of the above

Question 7

What is the function of incretin?

Accepted Answer

Increased insulin secretion

Answer

Increased heart rate

Answer

Increased respiratory rate

Answer

Stimulate erythropoiesis

Question 8

Insulin secretion is inhibited by which of the following substances?

Accepted Answer

Epinephrine

Answer

Secretin

Answer

Growth hormone

Answer

Gastrin

Question 9

In a seriously ill patient, the addition of amino acids to the diet results in a positive nitrogen balance. What is the primary mechanism for this?

Accepted Answer

Increased secretion of insulin

Answer

Increased growth hormone secretion

Answer

Enhanced rate of gluconeogenesis

Answer

Increased absorption of amino acids from the diet

Question 10

Insulin decreases:

Accepted Answer

Lipolysis

Answer

Glucose uptake

Answer

Glycogen synthesis

Answer

Protein synthesis

Endocrinology — MCQs

Endocrinology — MCQs

On this page

Practice by Chapter

Want unlimited practice?