Endocrinology Practice Questions

Q: Which of the following hormones is NOT secreted by the anterior pituitary?

Oxytocin. **Explanation:** The pituitary gland (hypophysis) is divided into the **Anterior Pituitary (Adenohypophysis)** and the **Posterior Pituitary (Neurohypophysis)**. The key distinction lies in their embryology and function: the anterior pituitary synthesizes its own hormones, whereas the posterior pituitary only stores and releases hormones produced in the hypothalamus. **Why Oxytocin is the Correct Answer:** Oxytocin is synthesized in the **paraventricular nuclei** (and to a lesser extent, the supraoptic nuclei) of the **hypothalamus**. It travels down the hypothalamo-hypophyseal tract to be stored in the posterior pituitary. Therefore, the posterior pituitary *releases* but does *not* secrete (synthesize) oxytocin. **Analysis of Incorrect Options:** * **Growth Hormone (GH):** Secreted by **Somatotrophs** in the anterior pituitary. It is the most abundant anterior pituitary hormone. * **FSH (Follicle-Stimulating Hormone):** A gonadotropin secreted by **Gonadotrophs** in the anterior pituitary. * **Prolactin:** Secreted by **Lactotrophs** (Mammotrophs) in the anterior pituitary. Unlike other hormones, its primary regulation is inhibitory (via Dopamine). **High-Yield NEET-PG Pearls:** 1. **Posterior Pituitary Hormones:** Only two—**Oxytocin** and **ADH (Vasopressin)**. Both are synthesized in the hypothalamus. 2. **Embryology:** The anterior pituitary develops from **Rathke’s pouch** (ectodermal outpocketing of the oropharynx), while the posterior pituitary develops from the **neuroectoderm** of the floor of the third ventricle. 3. **Cell Types:** Acidophils (GH, Prolactin) and Basophils (FSH, LH, ACTH, TSH). Remember the mnemonic: **"B-FLAT"** for Basophils.

Q: Which hormone is secreted by alpha-cells in the pancreas in response to low blood glucose levels?

Glucagon. **Explanation:** The pancreas functions as both an exocrine and endocrine gland. The endocrine component consists of the **Islets of Langerhans**, which contain several distinct cell types. **1. Why Glucagon is Correct:** **Glucagon** is synthesized and secreted by the **alpha (α) cells**, which constitute about 20% of the islet cells. Its primary stimulus is **hypoglycemia** (low blood glucose). Glucagon acts as a counter-regulatory hormone to insulin; it increases blood glucose levels by stimulating **glycogenolysis** (breakdown of glycogen) and **gluconeogenesis** (synthesis of glucose from non-carbohydrate sources) in the liver. **2. Why Other Options are Incorrect:** * **Insulin:** Secreted by **beta (β) cells** (the most abundant type, ~65-70%). It is released in response to *high* blood glucose levels to facilitate glucose uptake into cells. * **Epinephrine:** While it also raises blood glucose, it is secreted by the **adrenal medulla**, not the pancreas. It acts during the "fight or flight" response. * **Somatostatin:** Secreted by **delta (δ) cells**. Its primary role is paracrine inhibition, suppressing the secretion of both insulin and glucagon. **3. NEET-PG High-Yield Pearls:** * **Major Stimulus:** The most potent stimulator for glucagon is a fall in blood glucose, but **increased amino acids** (especially arginine and alanine) also stimulate its release. * **Inhibitors:** Glucagon secretion is inhibited by hyperglycemia, insulin, and somatostatin. * **Glucagonoma:** A rare tumor of alpha cells characterized by the "4 Ds": Diabetes, Dermatitis (Necrolytic migratory erythema), Deep vein thrombosis, and Depression. * **Clinical Use:** Intramuscular glucagon is used as emergency treatment for severe hypoglycemia in diabetic patients.

Q: Disorganized lesions in which of the following locations would affect the release of ADH and oxytocin from the posterior pituitary?

Supraoptic and paraventricular nuclei. **Explanation:** The posterior pituitary (neurohypophysis) does not synthesize hormones; instead, it stores and releases hormones produced in the hypothalamus. **1. Why Option A is Correct:** The hormones **Antidiuretic Hormone (ADH/Vasopressin)** and **Oxytocin** are synthesized in the cell bodies of magnocellular neurons located in the **Supraoptic (SON)** and **Paraventricular (PVN)** nuclei of the hypothalamus. * **SON** primarily synthesizes ADH. * **PVN** primarily synthesizes Oxytocin. These hormones are transported down the axons via the hypothalamo-hypophyseal tract (bound to carrier proteins called **neurophysins**) and are stored in terminal nerve endings (Herring bodies) in the posterior pituitary until release. Therefore, lesions in these nuclei directly disrupt the production and subsequent release of these hormones. **2. Why Other Options are Incorrect:** * **B. Ventromedial Nucleus:** Known as the **Satiety Center**. Lesions here lead to hyperphagia and obesity. * **C. Lateral Hypothalamus:** Known as the **Feeding Center**. Lesions here lead to aphagia and weight loss. * **D. Posterior Hypothalamus:** Primarily involved in **thermogenesis** (response to cold) and sympathetic regulation. Lesions result in poikilothermia (inability to regulate body temperature). **High-Yield Clinical Pearls for NEET-PG:** * **Diabetes Insipidus (DI):** Central DI occurs due to a deficiency of ADH, often resulting from trauma or lesions to the SON/PVN or the pituitary stalk. * **Neurophysins:** Neurophysin I is associated with Oxytocin, while Neurophysin II is associated with ADH. * **V2 Receptors:** ADH acts on V2 receptors in the collecting ducts of the kidney to insert Aquaporin-2 channels for water reabsorption.

Q: Diabetes insipidus is due to hyposecretion of which hormone?

Arginine Vasopressin/ AVP. **Explanation:** **Diabetes Insipidus (DI)** is a clinical syndrome characterized by the excretion of large volumes of dilute urine (polyuria) and excessive thirst (polydipsia). It occurs due to a deficiency in the action of **Arginine Vasopressin (AVP)**, also known as Antidiuretic Hormone (ADH). 1. **Why Arginine Vasopressin (AVP) is correct:** AVP is synthesized in the hypothalamus and stored in the posterior pituitary. Its primary role is to maintain water homeostasis by binding to V2 receptors in the renal collecting ducts, promoting the insertion of aquaporin-2 channels. This allows water reabsorption. **Hyposecretion** of AVP (Central DI) or resistance to its action (Nephrogenic DI) leads to an inability to concentrate urine, resulting in the hallmark symptoms of DI. 2. **Why other options are incorrect:** * **Insulin:** Hyposecretion of insulin leads to **Diabetes Mellitus**, characterized by hyperglycemia and osmotic diuresis due to glycosuria. * **Angiotensin:** Part of the RAAS pathway, Angiotensin II is a potent vasoconstrictor and stimulates aldosterone release; its deficiency does not cause DI. * **Aldosterone:** A mineralocorticoid responsible for sodium reabsorption and potassium excretion. Deficiency (as in Addison’s disease) leads to hyponatremia and hyperkalemia, not DI. **High-Yield Clinical Pearls for NEET-PG:** * **Water Deprivation Test:** The gold standard for diagnosing DI and differentiating it from primary polydipsia. * **Desmopressin (dDAVP):** A synthetic analog of AVP used to differentiate Central DI (responds to dDAVP) from Nephrogenic DI (no response). * **Urine Osmolality:** In DI, urine is characteristically dilute (typically <300 mOsm/kg).

Q: Which of the following receptors is NOT found in the nucleus?

Androgen receptor. To answer this question correctly, it is essential to distinguish between the two types of intracellular receptors: **Cytoplasmic** and **Nuclear**. ### **Why Androgen Receptor is the Correct Answer** The **Androgen receptor (Option B)**, along with Glucocorticoid, Mineralocorticoid, and Progesterone receptors, is primarily located in the **cytoplasm** in its inactive state. These receptors are bound to heat shock proteins (HSPs). Upon ligand binding, the receptor dissociates from the HSP, undergoes dimerization, and translocates into the nucleus to act as a transcription factor. ### **Analysis of Incorrect Options** * **Estrogen Receptor (Option A):** Unlike other steroid receptors, the Estrogen receptor is predominantly located **inside the nucleus**, even in its unbound state. * **Thyroxine (T3/T4) Receptor (Option C):** Thyroid hormone receptors are classic examples of **constitutive nuclear receptors**. They are always bound to DNA (Thyroid Response Elements), often acting as repressors until the hormone binds. * **Vitamin D Receptor (Option D):** Similar to Thyroid and Retinoic acid receptors, the Vitamin D receptor (VDR) is located **within the nucleus**. ### **High-Yield NEET-PG Pearls** * **Mnemonic for Cytoplasmic Receptors:** **"M-A-G-P"** (Mineralocorticoid, Androgen, Glucocorticoid, Progesterone). * **Nuclear Receptors:** Remember **"T-E-V-R"** (Thyroid, Estrogen, Vitamin D, Retinoic Acid). * **Mechanism:** All these receptors belong to the **Steroid Hormone Receptor Superfamily** and regulate gene expression by binding to specific DNA sequences called Hormone Response Elements (HREs). * **Exception:** While Estrogen is a steroid, its receptor is a notable exception as it resides in the nucleus, not the cytoplasm.

Q: Which hormone is secreted by the posterior pituitary gland?

Antidiuretic Hormone (ADH). **Explanation:** The posterior pituitary gland (neurohypophysis) does not synthesize hormones; instead, it stores and releases two hormones produced by the hypothalamus: **Antidiuretic Hormone (ADH/Vasopressin)** and **Oxytocin**. ADH is synthesized primarily in the **supraoptic nucleus**, while Oxytocin is synthesized in the **paraventricular nucleus**. They travel down the hypothalamo-hypophyseal tract and are released into the systemic circulation from the posterior pituitary in response to physiological triggers like increased plasma osmolarity. **Analysis of Incorrect Options:** * **A, B, and D (GH, TSH, FSH):** These are all synthesized and secreted by the **Anterior Pituitary (Adenohypophysis)**. The anterior pituitary contains specialized glandular cells (Somatotrophs for GH, Thyrotrophs for TSH, and Gonadotrophs for FSH/LH) regulated by hypothalamic releasing hormones. **NEET-PG High-Yield Pearls:** * **Storage Site:** Hormones in the posterior pituitary are stored in terminal nerve endings called **Herring Bodies**. * **ADH Receptors:** * **V1 receptors:** Located on vascular smooth muscle (cause vasoconstriction). * **V2 receptors:** Located in the late distal tubule and collecting ducts (increase water reabsorption via **Aquaporin-2** channels). * **Clinical Correlation:** A deficiency in ADH secretion or action leads to **Diabetes Insipidus**, characterized by polyuria and polydipsia. * **Mnemonic:** Remember **"FLAT PIG"** for Anterior Pituitary hormones (FSH, LH, ACTH, TSH, Prolactin, GH). If it’s not on this list, it’s likely Posterior Pituitary.

Question 1

Which of the following hormones is NOT secreted by the anterior pituitary?

Accepted Answer

Oxytocin

Answer

Growth hormone

Answer

FSH

Answer

Prolactin

Question 2

What is the mechanism of action of Calcitriol?

Accepted Answer

Increased calcium absorption from the intestine

Answer

Decreased calcium resorption from bone

Answer

Decreased calcium absorption from the kidney

Answer

Decreased calcium absorption from the intestine

Question 3

Posterior pituitary hormone secretion is mediated by which of the following mechanisms?

Accepted Answer

The hypothalamo-hypophyseal tract originating from magnocellular neurons in the supraoptic and paraventricular nuclei

Answer

A portal capillary system from the hypothalamus to the posterior pituitary

Answer

The fight-or-flight response

Answer

The reticular activating system's input to the hypothalamus

Question 4

Increased blood levels of cholesterol seen in hypothyroidism are most likely due to which of the following mechanisms?

Accepted Answer

Decreased production of LDL receptors in adipose tissue and increased release of cholesterol from adipose tissue

Answer

Decreased calorigenesis

Answer

Decreased production of LDL receptors in the liver, leading to decreased hepatic clearance

Answer

Increased breakdown of lipoproteins releasing cholesterol into circulation

Question 5

Which hormone is secreted by alpha-cells in the pancreas in response to low blood glucose levels?

Accepted Answer

Glucagon

Answer

Insulin

Answer

Epinephrine

Answer

Somatostatin

Question 6

Disorganized lesions in which of the following locations would affect the release of ADH and oxytocin from the posterior pituitary?

Accepted Answer

Supraoptic and paraventricular nuclei

Answer

Ventromedial part of the hypothalamus

Answer

Lateral hypothalamus

Answer

Posterior hypothalamus

Question 7

Diabetes insipidus is due to hyposecretion of which hormone?

Accepted Answer

Arginine Vasopressin/ AVP

Answer

Insulin

Answer

Angiotensin

Answer

Aldosterone

Question 8

Which of the following statements is true regarding calcium and phosphorus metabolism?

Accepted Answer

Calcitriol increases phosphate reabsorption in the proximal convoluted tubule.

Answer

Parathormone increases phosphate reabsorption in the proximal convoluted tubule.

Answer

Parathormone increases calcium reabsorption in the proximal convoluted tubule.

Answer

Calcitriol decreases phosphate absorption in the intestine.

Question 9

Which of the following receptors is NOT found in the nucleus?

Accepted Answer

Androgen receptor

Answer

Estrogen receptor

Answer

Thyroxine receptor

Answer

Vitamin D receptor

Question 10

Which hormone is secreted by the posterior pituitary gland?

Accepted Answer

Antidiuretic Hormone (ADH)

Answer

Growth Hormone (GH)

Answer

Thyroid Stimulating Hormone (TSH)

Answer

Follicle Stimulating Hormone (FSH)

Endocrinology — MCQs

Endocrinology — MCQs

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