Questions and Answers
with Rationales | 2026 Updated | 100%
Correct
Question
What is the first step in the synthesis of thyroid hormones?
A) Oxidation of iodide to iodine
B) Iodide trapped by thyroid follicular cells
C) Combination of DIT molecules to form T4
D) Release of T4 and T3 into circulation
Expert Rationale: The first step in thyroid hormone synthesis is the trapping of iodide (I⁻)
by thyroid follicular cells. This is followed by diffusion to the apex, transport into the colloid,
oxidation, and incorporation into tyrosine residues. T4 and T3 are released at the end of the
process.
Question
Insulin is best described as:
A) The hyperglycemic factor that mobilizes glycogen stores
B) The storage and anabolic hormone of the body
C) A hormone that promotes glycogenolysis
D) A hormone that increases blood glucose levels
Expert Rationale: Insulin is the storage and anabolic hormone of the body. It promotes the
synthesis and storage of glycogen, triglycerides, and protein in target tissues (liver, fat,
muscle). Glucagon is the hyperglycemic factor that mobilizes glycogen.
Question
Insulin is synthesized as which precursor?
,A) Preproinsulin
B) Proinsulin
C) C-peptide
D) Hexameric crystals
Expert Rationale: Insulin is synthesized as preproinsulin, which is processed to proinsulin.
Proinsulin is then converted to insulin and C-peptide and stored in secretory granules.
Insulin is stored in beta cells in the form of hexameric crystals.
Question
Which of the following stimulates insulin release?
A) Diazoxide
B) Somatostatin
C) Glucagon-like polypeptide 1 (GLP-1)
D) Phenytoin
Expert Rationale: GLP-1 is a hormone that stimulates insulin release. Other stimulators
include glucose, amino acids, and β-adrenergic sympathetic activity. Diazoxide,
somatostatin, and phenytoin are inhibitors of insulin release.
Question
Which drug inhibits insulin release?
A) Isoproterenol
B) Sulfonylureas
C) Diazoxide
D) Acetylcholine
Expert Rationale: Diazoxide inhibits insulin release. Sulfonylureas, meglitinides,
isoproterenol, and acetylcholine stimulate insulin release. Diazoxide opens ATP-sensitive
K+ channels, preventing depolarization and insulin secretion.
Question
What is the mechanism of glucose-stimulated insulin release?
A) Increased ATP closes K+ channels → depolarization → Ca2+ influx → insulin secretion
B) Increased ATP opens K+ channels → hyperpolarization → insulin secretion
,C) Decreased ATP closes Ca2+ channels → insulin secretion
D) Increased glucose directly stimulates exocytosis of insulin granules
Expert Rationale: Glucose metabolism increases ATP, which closes ATP-sensitive K+
channels. This depolarizes the cell, opens voltage-gated Ca2+ channels, and increases
intracellular Ca2+, triggering insulin exocytosis. This is the classic mechanism of glucose-
stimulated insulin release.
Question
Which of the following is an effect of insulin on the liver?
A) Promotes glycogenolysis
B) Promotes gluconeogenesis
C) Inhibits glycogenolysis and promotes glycogen synthesis
D) Promotes ketogenesis
Expert Rationale: Insulin promotes glucose storage as glycogen in the liver by inducing
glucokinase and glycogen synthase and inhibiting phosphorylase. It also inhibits
glycogenolysis, gluconeogenesis, and ketogenesis. Insulin is an anabolic hormone.
Question
Glucagon is synthesized in which cells?
A) Beta cells of the pancreas
B) Alpha cells of the pancreatic islets of Langerhans
C) Delta cells of the pancreas
D) The liver
Expert Rationale: Glucagon is synthesized in the alpha cells of the pancreatic islets of
Langerhans. Insulin is synthesized in beta cells; somatostatin in delta cells. Glucagon is a
peptide hormone consisting of 29 amino acids.
Question
What is the half-life of glucagon?
A) 1-2 hours
B) 3-6 months
, C) 3-6 minutes
D) 24 hours
Expert Rationale: Glucagon has a half-life of 3-6 minutes. It is degraded in the liver, kidney,
plasma, and at its tissue receptors. This short half-life allows for rapid regulation of blood
glucose.
Question
What is the primary use of glucagon?
A) Treatment of hyperglycemia
B) Emergency treatment of severe hypoglycemia when the patient cannot take oral glucose
C) Treatment of diabetic ketoacidosis
D) Weight loss management
Expert Rationale: Glucagon is used for the emergency treatment of severe hypoglycemia
in patients with diabetes who cannot self-administer oral glucose. It can be given IV, IM,
subcutaneously, or as a nasal powder.
Question
Which of the following is a contraindication to glucagon use?
A) Diabetes mellitus
B) Pheochromocytoma
C) Hypoglycemia
D) Hyperkalemia
Expert Rationale: Glucagon is contraindicated in patients with pheochromocytoma
because it can cause the release of catecholamines and increase blood pressure. It is also
contraindicated in patients with insulinoma due to the risk of rebound hypoglycemia.
Question
Regular insulin has an onset of action of approximately:
A) 15 minutes
B) 30 minutes
C) 1 hour
D) 2 hours
with Rationales | 2026 Updated | 100%
Correct
Question
What is the first step in the synthesis of thyroid hormones?
A) Oxidation of iodide to iodine
B) Iodide trapped by thyroid follicular cells
C) Combination of DIT molecules to form T4
D) Release of T4 and T3 into circulation
Expert Rationale: The first step in thyroid hormone synthesis is the trapping of iodide (I⁻)
by thyroid follicular cells. This is followed by diffusion to the apex, transport into the colloid,
oxidation, and incorporation into tyrosine residues. T4 and T3 are released at the end of the
process.
Question
Insulin is best described as:
A) The hyperglycemic factor that mobilizes glycogen stores
B) The storage and anabolic hormone of the body
C) A hormone that promotes glycogenolysis
D) A hormone that increases blood glucose levels
Expert Rationale: Insulin is the storage and anabolic hormone of the body. It promotes the
synthesis and storage of glycogen, triglycerides, and protein in target tissues (liver, fat,
muscle). Glucagon is the hyperglycemic factor that mobilizes glycogen.
Question
Insulin is synthesized as which precursor?
,A) Preproinsulin
B) Proinsulin
C) C-peptide
D) Hexameric crystals
Expert Rationale: Insulin is synthesized as preproinsulin, which is processed to proinsulin.
Proinsulin is then converted to insulin and C-peptide and stored in secretory granules.
Insulin is stored in beta cells in the form of hexameric crystals.
Question
Which of the following stimulates insulin release?
A) Diazoxide
B) Somatostatin
C) Glucagon-like polypeptide 1 (GLP-1)
D) Phenytoin
Expert Rationale: GLP-1 is a hormone that stimulates insulin release. Other stimulators
include glucose, amino acids, and β-adrenergic sympathetic activity. Diazoxide,
somatostatin, and phenytoin are inhibitors of insulin release.
Question
Which drug inhibits insulin release?
A) Isoproterenol
B) Sulfonylureas
C) Diazoxide
D) Acetylcholine
Expert Rationale: Diazoxide inhibits insulin release. Sulfonylureas, meglitinides,
isoproterenol, and acetylcholine stimulate insulin release. Diazoxide opens ATP-sensitive
K+ channels, preventing depolarization and insulin secretion.
Question
What is the mechanism of glucose-stimulated insulin release?
A) Increased ATP closes K+ channels → depolarization → Ca2+ influx → insulin secretion
B) Increased ATP opens K+ channels → hyperpolarization → insulin secretion
,C) Decreased ATP closes Ca2+ channels → insulin secretion
D) Increased glucose directly stimulates exocytosis of insulin granules
Expert Rationale: Glucose metabolism increases ATP, which closes ATP-sensitive K+
channels. This depolarizes the cell, opens voltage-gated Ca2+ channels, and increases
intracellular Ca2+, triggering insulin exocytosis. This is the classic mechanism of glucose-
stimulated insulin release.
Question
Which of the following is an effect of insulin on the liver?
A) Promotes glycogenolysis
B) Promotes gluconeogenesis
C) Inhibits glycogenolysis and promotes glycogen synthesis
D) Promotes ketogenesis
Expert Rationale: Insulin promotes glucose storage as glycogen in the liver by inducing
glucokinase and glycogen synthase and inhibiting phosphorylase. It also inhibits
glycogenolysis, gluconeogenesis, and ketogenesis. Insulin is an anabolic hormone.
Question
Glucagon is synthesized in which cells?
A) Beta cells of the pancreas
B) Alpha cells of the pancreatic islets of Langerhans
C) Delta cells of the pancreas
D) The liver
Expert Rationale: Glucagon is synthesized in the alpha cells of the pancreatic islets of
Langerhans. Insulin is synthesized in beta cells; somatostatin in delta cells. Glucagon is a
peptide hormone consisting of 29 amino acids.
Question
What is the half-life of glucagon?
A) 1-2 hours
B) 3-6 months
, C) 3-6 minutes
D) 24 hours
Expert Rationale: Glucagon has a half-life of 3-6 minutes. It is degraded in the liver, kidney,
plasma, and at its tissue receptors. This short half-life allows for rapid regulation of blood
glucose.
Question
What is the primary use of glucagon?
A) Treatment of hyperglycemia
B) Emergency treatment of severe hypoglycemia when the patient cannot take oral glucose
C) Treatment of diabetic ketoacidosis
D) Weight loss management
Expert Rationale: Glucagon is used for the emergency treatment of severe hypoglycemia
in patients with diabetes who cannot self-administer oral glucose. It can be given IV, IM,
subcutaneously, or as a nasal powder.
Question
Which of the following is a contraindication to glucagon use?
A) Diabetes mellitus
B) Pheochromocytoma
C) Hypoglycemia
D) Hyperkalemia
Expert Rationale: Glucagon is contraindicated in patients with pheochromocytoma
because it can cause the release of catecholamines and increase blood pressure. It is also
contraindicated in patients with insulinoma due to the risk of rebound hypoglycemia.
Question
Regular insulin has an onset of action of approximately:
A) 15 minutes
B) 30 minutes
C) 1 hour
D) 2 hours
