Endocrine System — MCQs
Thyroxine binding globulin (TBG) is increased in:
Increased insulin is characterized by all of the following, except:
Which of the following hormones is released from the posterior pituitary?
Which hormone does not act through cAMP?
Calcitonin levels increased in
Ducts of Bellini are present in:
What structures are derived from the neural crest?
All are derived from ectoderm except for which of the following?
Which of the following cell types is neuroectodermal in origin?
Which of the following does not form a visceral relation with the spleen?
Endocrine System Indian Medical PG Practice Questions and MCQs
Question 1: Thyroxine binding globulin (TBG) is increased in:
- A. Pregnancy (Correct Answer)
- B. Cancer chemotherapy
- C. Nephrotic syndrome
- D. Glucocorticoid therapy
Explanation: ***Pregnancy*** - Estrogen levels are elevated during **pregnancy**, which leads to an increase in the synthesis of **TBG** by the liver. - Increased TBG binds more thyroid hormone, reducing free thyroid hormone levels, which then stimulates the thyroid gland to produce more. *Cancer chemotherapy* - Many **chemotherapeutic agents** can damage the liver or interfere with protein synthesis, potentially leading to a *decrease* in TBG and other plasma proteins. - Chemotherapy can also induce **hypothyroidism** directly or indirectly, which may alter thyroid hormone binding. *Nephrotic syndrome* - **Nephrotic syndrome** is characterized by significant proteinuria, where plasma proteins, including **TBG**, are lost through the kidneys in the urine. - This leads to a *decrease* in serum TBG levels, which can affect total thyroid hormone measurements but typically does not cause overt thyroid dysfunction due to compensatory mechanisms. *Glucocorticoid therapy* - **Glucocorticoids** (e.g., prednisone, dexamethasone) are known to *decrease* the hepatic synthesis of **TBG**. - This reduction in TBG can lead to lower total thyroid hormone levels without necessarily indicating thyroid gland dysfunction, as free thyroid hormone levels often remain normal.
Question 2: Increased insulin is characterized by all of the following, except:
- A. Hypoglycemia
- B. Enhanced fatty acid synthesis
- C. Increased Intracellular potassium
- D. Increased Glucagon secretion (Correct Answer)
Explanation: ***Increased Glucagon secretion*** - **Insulin** primarily functions to lower blood glucose, and its release is typically inhibited by factors that trigger **glucagon** secretion, which aims to raise blood glucose. - Increased insulin would generally lead to **decreased glucagon secretion** as the body attempts to maintain glucose homeostasis. *Increased Intracellular potassium* - Insulin promotes the uptake of **potassium** into cells, particularly muscle and liver cells, by stimulating the **Na+/K+ ATPase pump**. - This action helps to lower serum potassium levels and can be utilized therapeutically in cases of hyperkalemia. *Hypoglycemia* - **Insulin** is the primary hormone responsible for lowering blood glucose levels by promoting glucose uptake by cells and inhibiting hepatic glucose production. - Excess insulin, whether endogenous or exogenous, can lead to **hypoglycemia** if glucose intake does not match insulin action. *Enhanced fatty acid synthesis* - **Insulin** is an anabolic hormone that promotes energy storage, including the conversion of excess glucose into **fatty acids** in the liver and adipose tissue. - This process, known as lipogenesis, is a key mechanism by which insulin contributes to the storage of energy reserves.
Question 3: Which of the following hormones is released from the posterior pituitary?
- A. Luteinizing hormone
- B. Growth hormone
- C. Antidiuretic hormone (Correct Answer)
- D. ACTH
Explanation: ***Antidiuretic hormone*** - The **posterior pituitary** (neurohypophysis) stores and releases **antidiuretic hormone (ADH)** and oxytocin. - ADH, also known as **vasopressin**, is synthesized in the **hypothalamus** and transported to the posterior pituitary for release. *Luteinizing hormone* - **Luteinizing hormone (LH)** is released from the **anterior pituitary** in response to gonadotropin-releasing hormone (GnRH) from the hypothalamus. - LH plays a crucial role in **reproduction**, triggering ovulation in females and testosterone production in males. *Growth hormone* - **Growth hormone (GH)** is synthesized and secreted by the **anterior pituitary gland**. - Its release is regulated by **growth hormone-releasing hormone (GHRH)** and **somatostatin** from the hypothalamus. *ACTH* - **Adrenocorticotropic hormone (ACTH)** is produced and secreted by the **anterior pituitary gland**. - ACTH stimulates the **adrenal cortex** to release cortisol, regulating stress responses and metabolism.
Question 4: Which hormone does not act through cAMP?
- A. TSH
- B. ACTH
- C. Insulin (Correct Answer)
- D. Adrenaline
Explanation: ***Insulin*** - Insulin primarily acts through a **tyrosine kinase receptor**, which, upon ligand binding, autophosphorylates and triggers downstream signaling cascades involving various protein kinases and phosphatases. - This mechanism allows insulin to mediate its diverse metabolic effects, such as glucose uptake and storage, independent of the **cAMP pathway**. *TSH (Thyroid-stimulating hormone)* - TSH binds to its receptor on thyroid follicular cells, activating **G protein-coupled receptors** that stimulate **adenylyl cyclase**. - This leads to an increase in intracellular **cAMP**, which then activates protein kinase A (PKA) to promote thyroid hormone synthesis and release. *ACTH (Adrenocorticotropic hormone)* - ACTH acts on the **adrenal cortex** through G protein-coupled receptors, stimulating **adenylyl cyclase** and raising intracellular **cAMP levels**. - Increased cAMP then activates PKA, leading to the synthesis and secretion of **cortisol** and other adrenal steroids. *Adrenaline (Epinephrine)* - Adrenaline can act through various **adrenergic receptors (alpha and beta)**; **beta-adrenergic receptors** are Gs protein-coupled and activate **adenylyl cyclase**. - This increases **cAMP** levels, mediating effects such as bronchodilation, increased heart rate, and glycogenolysis.
Question 5: Calcitonin levels increased in
- A. Hypoparathyroidism
- B. Cushing Syndrome
- C. Medullary thyroid carcinoma (Correct Answer)
- D. Hyperparathyroidism
Explanation: Medullary thyroid carcinoma - Calcitonin is a hormone produced by the parafollicular C cells of the thyroid gland. - Medullary thyroid carcinoma is a neuroendocrine tumor arising from these C cells, leading to excessive and unregulated calcitonin production. Hyperparathyroidism - This condition involves increased production of parathyroid hormone (PTH), which acts to increase serum calcium levels [2]. - Calcitonin secretion is typically decreased or normal in hyperparathyroidism, as calcitonin works to lower serum calcium. Hypoparathyroidism - This condition is characterized by insufficient production of parathyroid hormone (PTH), leading to low serum calcium levels [1]. - Calcitonin levels are generally unaffected or may even be slightly decreased in response to the low calcium, as its primary role is to lower calcium. Cushing Syndrome - Cushing Syndrome is caused by prolonged exposure to high levels of cortisol, a glucocorticoid. - While cortisol can affect bone metabolism, it does not directly impact calcitonin production or secretion, which is primarily regulated by serum calcium levels and C-cell activity.
Question 6: Ducts of Bellini are present in:
- A. Pancreas
- B. Liver
- C. Kidney (Correct Answer)
- D. Salivary gland
Explanation: ***Kidney*** - The Ducts of Bellini, also known as **large papillary collecting ducts**, are the terminal portions of the collecting duct system in the kidney. - They are located in the **renal medulla**, particularly within the renal papillae, and drain urine into the minor calyces. *Pancreas* - The pancreas is involved in **digestion** and hormone production (e.g., insulin), not urine formation. - Its duct system includes the **main pancreatic duct (Wirsung's duct)** and accessory pancreatic duct. *Liver* - The liver's primary functions are **metabolism**, detoxification, and bile production. Its duct system consists of **bile ducts**, which transport bile, not urine [1], [2]. - Its duct system consists of **bile ducts**, which transport bile, not urine. *Salivary gland* - Salivary glands produce **saliva** and have their own unique duct systems (e.g., Wharton's duct, Stensen's duct). - These glands are part of the digestive system and are not involved in renal function.
Question 7: What structures are derived from the neural crest?
- A. Melanocytes
- B. Dental papillae
- C. Adrenal medulla
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - The **neural crest** is a multipotent, migratory cell population that contributes to the formation of many diverse tissues and organs during vertebrate development. - Neural crest cells give rise to a wide array of derivatives, including components of the nervous system, pigment cells, skeletal and connective tissues of the head and face, and endocrine glands [1]. *Melanocytes* - **Melanocytes**, the pigment-producing cells found in the skin, hair, eyes, and other tissues, are derived from the **neural crest** [2]. - These cells migrate extensively during development from the neural crest to their final destinations throughout the body. - Neural crest-derived melanocytes produce melanin, which provides pigmentation and protection against UV radiation [2]. *Dental papillae* - The **dental papilla** is crucial for tooth development and is formed from **ectomesenchymal cells** that are derived from the cranial neural crest. - These cells differentiate into the odontoblasts that produce dentin and also contribute to the pulp of the tooth. *Adrenal medulla* - The cells of the **adrenal medulla**, which produce catecholamines like epinephrine and norepinephrine, are specialized **postganglionic sympathetic neurons** derived from the neural crest. - They develop from neuroectodermal cells that migrate to the developing adrenal gland.
Question 8: All are derived from ectoderm except for which of the following?
- A. Hair follicles
- B. Nails
- C. Lens of the eye
- D. Adrenal cortex (Correct Answer)
Explanation: ***Adrenal cortex*** - The adrenal cortex is derived from the **intermediate mesoderm**, specifically from the cells lining the posterior abdominal wall. The cells migrate to develop into the adrenal cortex. - It produces various steroid hormones, including **aldosterone**, **cortisol**, and **androgens**, which regulate diverse bodily functions. *Lens of the eye* - The lens of the eye is derived from the **surface ectoderm**. It forms from an invagination of the surface ectoderm called the lens placode. - Its primary function is to **focus light** onto the retina. *Hair follicles* - Hair follicles develop from the **surface ectoderm** [1]; they are invaginations of the epidermis that extend into the dermis. - They produce hair, which provides **insulation** and **protection** [1]. *Nails* - Nails are also derivatives of the **surface ectoderm**, forming thickened plates on the dorsal surface of the distal phalanges. - They provide **protection** to the fingertips and aid in grasping objects.
Question 9: Which of the following cell types is neuroectodermal in origin?
- A. Smooth muscle cells (Correct Answer)
- B. Skeletal muscle cells
- C. Endothelial cells
- D. Cardiac muscle cells
Explanation: ***Smooth muscle cells*** - This is the **correct answer** based on a **specific exception**: smooth muscle cells of the **iris dilator and sphincter muscles** and the **ciliary muscle** in the eye are derived from **neuroectoderm** (specifically from the **optic cup**, an outgrowth of the neural tube). - **Important note:** The vast majority of smooth muscle in the body is of **mesodermal origin** (e.g., in blood vessels, GI tract, respiratory tract). This question tests knowledge of this **notable embryological exception**. - In the context of the given options, this is the only cell type with any neuroectodermal component. *Skeletal muscle cells* - Skeletal muscle cells are entirely derived from the **paraxial mesoderm**, specifically from **somites** (myotome portion). - They form the voluntary muscles of the body and are **never** of neuroectodermal origin. *Endothelial cells* - Endothelial cells lining blood vessels and lymphatic vessels are derived from the **mesoderm** (specifically from **angioblasts**). - They are part of the cardiovascular system and are **entirely mesodermal** in origin. *Cardiac muscle cells* - Cardiac muscle cells are derived from the **splanchnic mesoderm** (lateral plate mesoderm). - The heart musculature is **entirely mesodermal** with no neuroectodermal contribution. **Clinical Pearl:** Classic neuroectodermal derivatives include neurons, glial cells (astrocytes, oligodendrocytes), ependymal cells, and neural crest derivatives (Schwann cells, melanocytes, chromaffin cells). The smooth muscle of the iris represents an important exception to the general rule that smooth muscle is mesodermal.
Question 10: Which of the following does not form a visceral relation with the spleen?
- A. Stomach
- B. Splenic flexure of colon
- C. Left kidney
- D. Adrenal glands (Correct Answer)
Explanation: The adrenal glands, specifically the **left adrenal gland**, are located superior to the **left kidney** but are generally not in direct visceral relation with the spleen itself [2]. The spleen's concavities accommodate other organs. The spleen is typically located in the **left hypochondrium**, nestled against the diaphragm, superior to the left kidney, but the adrenal gland is usually separated by the kidney or surrounding fascia. *Stomach* - The **gastric impression** on the spleen's anterior surface is formed by the fundus of the **stomach**, indicating a direct visceral relation [3]. - The stomach is one of the primary organs that directly abuts the spleen's visceral surface. *Splenic flexure of colon* - The **colic impression** on the inferior aspect of the spleen is formed by the **splenic flexure of the colon**, confirming a direct visceral relation [1]. - This anatomical arrangement explains why an enlarged spleen can sometimes be palpated near the colon. *Left kidney* - The **renal impression** on the posterior aspect of the spleen is formed by the anterior superior surface of the **left kidney**, establishing a clear visceral relation [1]. - The spleen lies directly superior and lateral to the left kidney.
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