Endocrinology Practice Questions

Q: Which of the following is NOT a function of parathyroid hormone (PTH)?

Decreases phosphate excretion. **Explanation:** Parathyroid Hormone (PTH) is the primary regulator of calcium and phosphate homeostasis. Its overarching goal is to **increase serum calcium** and **decrease serum phosphate**. **Why Option C is the Correct Answer:** PTH **increases** phosphate excretion (phosphaturia), it does not decrease it. It acts on the proximal convoluted tubule (PCT) of the kidney to inhibit the sodium-phosphate cotransporter (NaPi-IIa), leading to decreased phosphate reabsorption. This is a physiological mechanism to prevent calcium-phosphate precipitation as serum calcium levels rise. **Analysis of Other Options:** * **A. Maintains serum calcium levels:** This is the primary function of PTH. It responds to hypocalcemia via calcium-sensing receptors (CaSR) to restore normalcy. * **B. Promotes calcium retention:** PTH increases calcium reabsorption in the distal convoluted tubule (DCT) and thick ascending limb of the loop of Henle, effectively "retaining" calcium in the body. * **D. May cause osteolysis:** In high concentrations (chronic elevation), PTH stimulates osteoclasts indirectly via the RANKL pathway, leading to bone resorption (osteolysis) to mobilize calcium into the blood. **NEET-PG High-Yield Pearls:** * **The "Phosphate Trashing" Hormone:** Remember the mnemonic: **"PTH: Phosphate Trashing Hormone"**—it dumps phosphate in the urine. * **Vitamin D Activation:** PTH stimulates **1-alpha-hydroxylase** in the kidney, converting 25-hydroxyvitamin D to its active form, 1,25-dihydroxyvitamin D (Calcitriol). * **Clinical Correlation:** In **Primary Hyperparathyroidism**, the classic biochemical profile is **Hypercalcemia + Hypophosphatemia + Hyperphosphaturia.**

Q: What is true about insulin?

It promotes the synthesis of triglycerides.. ### Explanation **Correct Answer: D. It promotes the synthesis of triglycerides.** Insulin is the primary **anabolic hormone** of the body. In adipose tissue, it promotes lipogenesis (the synthesis of triglycerides) by increasing the transport of glucose into adipocytes via GLUT-4 and activating **Lipoprotein Lipase (LPL)**, which breaks down circulating chylomicrons into free fatty acids for storage. Simultaneously, it inhibits **Hormone-Sensitive Lipase (HSL)**, thereby preventing lipolysis. **Analysis of Incorrect Options:** * **A. Its release is enhanced by somatostatin:** This is incorrect. Somatostatin (produced by delta cells of the pancreas) acts as a universal inhibitor; it **inhibits** the secretion of both insulin and glucagon via paracrine signaling. * **B. It has an identical chemical structure in all species:** This is incorrect. While the basic structure (A and B chains linked by disulfide bonds) is conserved, amino acid sequences vary. For example, **porcine insulin** differs from human insulin by one amino acid (Alanine instead of Threonine at position B30), while bovine insulin differs by three. * **C. It is released from the pancreas only in the postprandial state:** This is incorrect. Insulin secretion is continuous. There is a **basal secretion** (approx. 1 unit/hour) to maintain glucose homeostasis during fasting, which spikes significantly (bolus secretion) in response to meals (postprandial). **High-Yield Clinical Pearls for NEET-PG:** * **GLUT-4** is the only insulin-dependent glucose transporter, found primarily in skeletal muscle and adipose tissue. * **C-peptide** is secreted in equimolar amounts with insulin; it is a key marker to distinguish endogenous insulin production from exogenous insulin injection (Factitious Hypoglycemia). * Insulin causes an **intracellular shift of potassium**, making it a standard treatment for acute hyperkalemia.

Q: In obesity, which of the following hormone levels is decreased?

Adiponectin. **Explanation:** In obesity, the adipose tissue undergoes structural and functional changes that alter its endocrine profile. While most adipokines (like Leptin) increase with increasing fat mass, **Adiponectin** is a notable exception. **1. Why Adiponectin is the Correct Answer:** Adiponectin is a protective adipokine that enhances insulin sensitivity and exerts anti-inflammatory and anti-atherogenic effects. In obesity, specifically central/visceral obesity, the expansion of adipocytes leads to increased production of pro-inflammatory cytokines (like TNF-α and IL-6). These cytokines **downregulate** the expression and secretion of adiponectin. Therefore, adiponectin levels are **inversely correlated** with Body Mass Index (BMI) and fat mass. Low levels contribute to the development of insulin resistance and metabolic syndrome. **2. Analysis of Incorrect Options:** * **Catecholamines (A):** Obesity is generally associated with increased sympathetic nervous system activity, leading to normal or elevated levels of catecholamines, which contribute to obesity-related hypertension. * **Insulin (B):** Obesity is a primary cause of insulin resistance. To compensate, the pancreas secretes more insulin, leading to **hyperinsulinemia**. * **Copeptin (D):** Copeptin is a surrogate marker for Arginine Vasopressin (AVP). Studies show that copeptin levels are typically elevated in obesity and metabolic syndrome, correlating with water retention and increased stress response. **High-Yield Clinical Pearls for NEET-PG:** * **The "Adiponectin Paradox":** Despite being produced by adipose tissue, its levels decrease as adipose tissue increases. * **Leptin vs. Adiponectin:** In obesity, **Leptin increases** (leading to leptin resistance), while **Adiponectin decreases**. * **Thiazolidinediones (TZDs):** Drugs like Pioglitazone work partly by increasing the expression of Adiponectin, thereby improving insulin sensitivity.

Q: Insulin release is inhibited by:

Somatostatin. ### Explanation **Correct Answer: A. Somatostatin** **Mechanism of Action:** Insulin secretion from the pancreatic **Beta cells** is regulated by a complex interplay of nutrients, hormones, and neural inputs. **Somatostatin**, secreted by the **Delta ($\delta$) cells** of the pancreas, acts as a potent universal inhibitor. It exerts a paracrine effect on neighboring Beta cells by binding to **SSTR-5 receptors**, which are coupled to inhibitory G-proteins ($G_i$). This leads to a decrease in intracellular cAMP and the inhibition of calcium influx, effectively shutting down insulin release. **Analysis of Incorrect Options:** * **B. Glucagon:** Secreted by Alpha cells, glucagon actually **stimulates** insulin release. This paracrine interaction ensures that as glucagon raises blood glucose, insulin is available to facilitate glucose uptake by peripheral tissues. * **C. Acetylcholine:** This is the primary neurotransmitter of the parasympathetic nervous system (Vagus nerve). It **stimulates** insulin secretion (via $M_3$ receptors) in anticipation of nutrient absorption during the "rest and digest" phase. * **D. Amino Acids:** Arginine and Lysine are potent **secretagogues** for insulin. Their presence signals a fed state, necessitating insulin for protein synthesis and glucose regulation. **High-Yield NEET-PG Pearls:** * **Most potent stimulator:** Glucose is the primary physiological stimulus for insulin. * **Incretin Effect:** Oral glucose causes a greater insulin response than IV glucose due to hormones like **GLP-1 and GIP**. * **Adrenergic Control:** $\alpha_2$-adrenergic stimulation **inhibits** insulin (dominant during stress/exercise), while $\beta_2$-stimulation **increases** it. * **Biphasic Release:** Insulin is released in two phases; the first phase is the release of pre-formed granules, and the second is the synthesis of new insulin.

Q: If a normal individual receives an insulin injection that lowers plasma glucose to 30 mg/dl, which of the following hormones will not be released?

Aldosterone. **Explanation:** The physiological response to hypoglycemia (plasma glucose <70 mg/dl) involves the activation of the **Counter-regulatory Hormone System**. This system aims to restore glucose levels through glycogenolysis and gluconeogenesis. **Why Aldosterone is the Correct Answer:** Aldosterone is a mineralocorticoid primarily regulated by the **Renin-Angiotensin-Aldosterone System (RAAS)** in response to low blood pressure or hypovolemia, and by serum **Potassium ($K^+$)** levels. It is not a counter-regulatory hormone. Hypoglycemia does not trigger the RAAS or significant electrolyte shifts that would necessitate aldosterone release. **Why the other options are incorrect:** * **ACTH (Option A):** Hypoglycemia is a potent stressor that activates the Hypothalamic-Pituitary-Adrenal (HPA) axis. The hypothalamus releases CRH, which stimulates the anterior pituitary to release **ACTH**, subsequently increasing **Cortisol**. Cortisol promotes gluconeogenesis. * **Epinephrine (Option B):** This is the "first line" rapid response to hypoglycemia. Low glucose triggers the sympathetic nervous system and the adrenal medulla to release epinephrine, which immediately stimulates hepatic glycogenolysis. * **Growth Hormone (Option C):** GH is released in response to hypoglycemia to decrease peripheral glucose utilization and promote lipolysis, acting as a glucose-sparing agent. **High-Yield NEET-PG Pearls:** 1. **Hierarchy of Response:** The first defense against hypoglycemia is the suppression of endogenous insulin, followed by a rise in **Glucagon** and **Epinephrine**. 2. **Insulin Tolerance Test (ITT):** Inducing hypoglycemia with insulin is the "Gold Standard" test to evaluate the integrity of the HPA axis and Growth Hormone reserve. 3. **Glucagon vs. Epinephrine:** Glucagon is the most important hormone for acute recovery from hypoglycemia in non-diabetics; however, if glucagon is deficient, epinephrine becomes critical.

Q: Cutting of the pituitary stalk decreases all of the following hormones except?

Prolactin. The secretion of anterior pituitary hormones is primarily regulated by the hypothalamus via the **hypothalamic-hypophyseal portal system**. Most anterior pituitary hormones (ACTH, TSH, growth hormone, FSH, LH) are under **stimulatory** control by hypothalamic releasing factors [1]. However, **Prolactin** is the unique exception; it is under tonic **inhibitory** control by **Dopamine** [3]. When the pituitary stalk is severed (Pituitary Stalk Interruption), the connection between the hypothalamus and the pituitary is lost. This results in: 1. **Decreased levels** of hormones that require hypothalamic stimulation (ACTH, GH, FSH, LH, and TSH). 2. **Increased levels** of Prolactin, because the inhibitory influence of Dopamine is removed [3]. This phenomenon is often referred to as "Stalk Effect" hyperprolactinemia. **Analysis of Options:** * **A, B, and D (ACTH, GH, FSH):** These are incorrect because their secretion depends on CRH, GHRH, and GnRH, respectively. Cutting the stalk prevents these releasing hormones from reaching the anterior pituitary, leading to a deficiency [4]. * **C (Prolactin):** This is the correct answer because its levels **increase** rather than decrease when the inhibitory dopaminergic pathway is disrupted. **High-Yield Clinical Pearls for NEET-PG:** * **Dopamine = Prolactin Inhibiting Factor:** Any drug that blocks dopamine (e.g., antipsychotics like Haloperidol or prokinetics like Metoclopramide) will cause hyperprolactinemia. * **Stalk Effect vs. Prolactinoma:** In stalk compression (e.g., by a Craniopharyngioma), prolactin levels are usually 200 ng/mL strongly suggest a Prolactinoma. * **Posterior Pituitary:** Stalk transection also leads to **Diabetes Insipidus** because ADH (Vasopressin) and Oxytocin, synthesized in the hypothalamus, can no longer be transported to the posterior pituitary for release [2].

Q: Which of the following statements regarding prolactin levels is TRUE?

Highest during pregnancy and fall during lactation. **Explanation:** **Understanding Prolactin Dynamics** The correct answer is **B**. During pregnancy, prolactin levels rise progressively, reaching their peak (up to 10–20 times non-pregnant levels) at term. This increase is driven by high levels of circulating **estrogen**, which stimulates the lactotrophs in the anterior pituitary to undergo hyperplasia and hypertrophy. Post-delivery, estrogen levels plummet. In non-breastfeeding women, prolactin returns to baseline within 2–3 weeks. In breastfeeding women, while basal prolactin remains elevated, it gradually **falls** over several months of lactation, though it spikes transiently during each episode of suckling (the neuroendocrine reflex). **Analysis of Incorrect Options:** * **Option A:** Incorrect. Prolactin is at its highest during pregnancy, not lowest. It does not increase *after* delivery; rather, the *action* of prolactin (lactogenesis) begins after delivery once the inhibitory effect of progesterone is removed. * **Option C:** Incorrect. Both pregnancy and lactation are the primary physiological states that significantly alter prolactin secretion. * **Option D:** Incorrect. Prolactin follows a highly predictable physiological pattern in all normal pregnancies. **High-Yield Clinical Pearls for NEET-PG:** * **The Progesterone Paradox:** Even though prolactin is high during pregnancy, milk secretion is inhibited by high **Progesterone** levels. Lactation only begins after the placenta is delivered and progesterone levels drop. * **Amniotic Fluid:** Prolactin is found in high concentrations in amniotic fluid, where it aids in fetal osmoregulation. * **Lactational Amenorrhea:** High prolactin inhibits **GnRH pulsatility**, leading to suppressed FSH/LH and subsequent anovulation. * **Drug of Choice:** For pathological hyperprolactinemia (Prolactinoma), the drug of choice is **Cabergoline** (a dopamine agonist).

Question 1

Which of the following is NOT a function of parathyroid hormone (PTH)?

Accepted Answer

Decreases phosphate excretion

Answer

Maintains serum calcium levels

Answer

Promotes calcium retention

Answer

May cause osteolysis

Question 2

What is true about insulin?

Accepted Answer

It promotes the synthesis of triglycerides.

Answer

Its release is enhanced by somatostatin.

Answer

It has an identical chemical structure in all species.

Answer

It is released from the pancreas only in the postprandial state.

Question 3

In obesity, which of the following hormone levels is decreased?

Accepted Answer

Adiponectin

Answer

Catecholamines

Answer

Insulin

Answer

Copeptin

Question 4

A 16-year-old girl diagnosed with anorexia nervosa presents with light-headedness, diaphoresis, and palpitations during exercise. Her serum glucose is 40 mg/dL. She improves after consuming a soft drink. Which of the following hormones most likely triggered the sweating and palpitations?

Accepted Answer

Epinephrine

Answer

ACTH

Answer

Calcitonin

Answer

Insulin

Question 5

Insulin release is inhibited by:

Accepted Answer

Somatostatin

Answer

Glucagon

Answer

Acetylcholine

Answer

Amino acids

Question 6

If a normal individual receives an insulin injection that lowers plasma glucose to 30 mg/dl, which of the following hormones will not be released?

Accepted Answer

Aldosterone

Answer

ACTH

Answer

Epinephrine

Answer

Growth hormone

Question 7

Cutting of the pituitary stalk decreases all of the following hormones except?

Accepted Answer

Prolactin

Answer

ACTH

Answer

GH

Answer

FSH

Question 8

Which of the following receptor genes controls TSH secretion?

Accepted Answer

TR beta 2

Answer

TR alpha 1

Answer

TR alpha 2

Answer

TR beta 1

Question 9

Which of the following is responsible for fasting hypoglycemia?

Accepted Answer

Increased insulin level

Answer

Decreased insulin level

Answer

Increased glycogen

Answer

Increased glucagon in the liver

Question 10

Which of the following statements regarding prolactin levels is TRUE?

Accepted Answer

Highest during pregnancy and fall during lactation

Answer

Lowest in pregnancy and increases after delivery

Answer

Unaffected by pregnancy and lactation

Answer

Variable in every pregnancy

Endocrinology — MCQs

Endocrinology — MCQs

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